African admixture in Europe
Encyclopedia
African admixture in Europe refers to the Eurasian presence of Human
genetic
polymorphisms
, which are considered to be evidence for movements of people from Africa to Eurasia in both the prehistoric and historic past.
and the Sahara Desert were formidable barriers to gene flow between Sub-Saharan Africa and Europe. But Europe and the Mediterranean were periodically more easily accessible to Africans due to fluctuations in the size and climate of the Sahara. At the Strait of Gibraltar
, Africa and Europe are separated by only 15 kilometres (9.3 mi) of water. At the Suez
, Eurasia
is connected to Africa forming a single land mass. The Nile river valley, which runs from East Africa
to the Mediterranean Sea could have served as a bidirectional corridor in the Sahara desert, that allows communication between Sub-Saharan Africa with the peoples of Eurasia.
first emerged in Africa 150,000-200,000 years ago. All non-Africans are descended from at least one group of humans who migrated out of Africa into western Asia 50,000-70,000 years ago. The first modern humans in Europe, the Cro-Magnon
, arrived from Western Asia and are believed to have completely replaced the previous inhabitants, the Neanderthal
s. Cro-Magnons were in the Middle East (Lebanon) by 45,000 years ago and in Eastern Europe by 40,000 years ago. By 30,000 years ago, the Cro-Magnon people had populated much of Europe. This was however not the last major human migration into Europe and this paleolithic population was to some extent replaced by later migrations to be discussed below.
, a period between 25,000 and 19,000 years ago, large ice sheets over a kilometer thick covered much of Northern Europe, making the region uninhabitable to humans. It is believed that human populations retreated south to warmer regions near the Mediterranean. Refuges during this period are believed to have been in Iberia
, the Balkans
and Italy
.
DNA evidence suggests that during the Last Glacial Maximum, there was some gene flow
from Africa into Iberia. After the Last Glacial Maximum, when the European climate warmed up, the refuges are thought to have been the source from which Europe was repopulated. African lineages that had been introduced into the Iberian refuge would have then dispersed all over Europe with the Northward expansion of humans. This could explain the presence of genetic lineages in Eastern Europe and as far North as Russia, that appear to have prehistoric links to Northwest and West Africa (see mtDNA). The expansion of human populations from Iberian refuges is also believed to have moved back to Northwest Africa.
to agriculture during the Neolithic Revolution
was a watershed in world history. The societies that first made the change to agriculture are believed to have lived in the Middle East around 10,000 BCE. Agriculture was introduced into Europe by migrating farmers from the Middle East. According to the demic diffusion
model, these Middle Eastern farmers either replaced or interbred with the local hunter-gather populations that had been living in Europe since the "out of Africa" migration.
It has been suggested that the first Middle Eastern farmers had African influences. There have been suggestions that some genetic lineages found in the Middle East arrived there during this period. The first Agricultural societies in the Middle East are generally thought to have emerged out of the Natufian Culture
, which existed in Palestine from 12,000 BCE-10,000 BCE. An important migration from Africa across the Sinai appears to have occurred before the formation of the Natufian.
and Sicily
during the time of the Islamic Golden Age
. The genetic effect of this period on modern European populations is the subject of discussion (see below). In more recent history, the peoples of Europe and Africa came into contact during the exploration
and colonisation of Africa
and as a consequence of the Atlantic slave trade
. As a result of these recent contacts, lineages of African descent have also been detected in Europe. In general, African admixture is distributed along a South-to-North cline, with peaks in the Mediterranean region and Iberia.
, sexual selection
, genetic drift
, population bottleneck
s, founder effects, isolation by distance
, genetic admixture
and barriers to gene flow
. The most influential factors affecting human genetic variation are founder effects and isolation by distance
.
Founder effect
occurs when a population is established by a small number of individuals who have departed from a much larger population. Several generations after the population has expanded, individuals will still possess the limited gene pool of the founders. Therefore founder effects result in a loss of genetic diversity
. Genetic evidence suggests that the out of Africa migration involved only small number of individuals. The African migrants carried a small subset of the prehistoric African genetic diversity, resulting in a founder effect of the Non-African population. As humans spread across the globe populating Eurasia, Australia and the Americas, there were several founder effects. As a result of these serial founder effects, genetic diversity tends to decrease with distance from Africa.
The other big factor contributing to patterns of human genetic variation is "Isolation by distance
". According to this model populations that live near each other are more likely to exchange mates than populations that live further apart. As a result populations that live near each other are genetically more similar than populations that live far apart.
Genetic distance
is a measure used to compare the genetic relationship between populations. It is based on the principle that populations that share similar frequencies of a trait are closer relations than populations that have different frequencies of a trait. The genetic distance between two populations increases linearly with the geographic distance between the two populations due to isolation by distance
and serial founder effects.Genetic admixture
increases the genetic diversity of a population. When admixture occurs between populations, the genetic distance between the two populations is reduced.
applied genetic distance measures to various populations around the world to infer phylogenetic relationships (see Table on the right). All non-African populations are more closely related to each other (i.e. short genetic distance) than they are to African populations. This is consistent with a founder effect of the non-African population in that only a few individuals participated in the initial out of Africa migration. The largest genetic distances observed are between Africa and Oceania and between Africa and the Americas. This is consistent with the isolation by distance and serial founder effects.
suggests that the genetic distance between Sub-Saharan Africa and Europe is anomalously lower than it should be if the two populations have been evolving independently. The study suggests that the lower genetic distance between Europe and Africa can be explained by genetic admixture.
ns and Sub-Saharan Africa
ns. Examples of such variants include the y-chromosomal
haplogroup E1b1b and mitochondrial haplogroup M1.
This sharing of polymorphisms is the result of long distance movements of peoples between Sub-Saharan Africa and Eurasia that involved traversing North Africa and sometimes the Middle East. Consequently the definitions of "African", "Sub-Saharan African" and "North African" will depend on the time frame of reference or the semantic preferences of any particular scientist. Due to prehistoric migrations in and out of Africa, North African populations tend to exhibit allele
frequencies that are intermediate between Sub-Saharan Africa and Eurasia
. Due to this complex genetic profile of Africa, African admixture in Europe could be the result of direct contact with Sub-Saharan Africans or indirectly through contact with North Africans with Sub-Saharan affiliations.
In some cases, lineages found in Africa and Europe may have a common origin in Asia
(for example Y haplogroups R1
, T
) and Haplogroup U. One clade of haplogroup U, U6a1 is known to have expanded from North and East Africa back into Europe . Other lineages are known to have moved from Europe directly into Africa (for example mitochondrial haplogroups H1, H3. Such back migrations between Africa and Eurasia also complicate defining admixture.
gene flow from Africa to Europe, via the Middle East, is thought to be E1b1b1, which is thought to have emerged about 22,000 years ago in East Africa
and branches of it are thought to have migrated to the Middle East
by 11,000 years ago during the late Pleistocene
or early Neolithic
periods.
Entering the late mesolithic
Natufian culture, the E1b1b1a2 (E-V13) sub-clade has been associated with the spread of farming from the Middle East into Europe either during or just before the Neolithic transition. E1b1b1 lineages are found throughout Europe but are distributed along a South-to-North cline, with a E1b1b1a mode
in the Balkans
.
In separate migrations, E lineages in the form of the E1b1b1b subclade appear to have entered Europe from Northwest Africa into Iberia. In a sample of European males, Cruciani et al. observed Haplogroup E at a frequencies of 7.2%. The timing of this movement has been given widely variant estimates.
A big expansion of peoples throughout Sub-Saharan Africa occurred after the introduction of agriculture 5,000 years ago. During the Bantu expansion
people carrying Haplogroup E
(not including E1b1b) lineages dispersed across much of Sub-Saharan Africa from their homeland near the border between Nigeria and Cameroon. The haplogroup most often associated with this expansion is E1b1a, which constitutes up to 48% of the African male gene pool. The presence of E1b1a lineages outside Africa can typically be associated with events that occurred after the Bantu Expansion, such as the trade in African slaves or the Moorish
occupation of Iberia
. In much of Europe frequencies of E lineages which are not E1b1b are very low, usually less than 1%. For example Cruciani et al. 2004, report such lineages at 2% in Southern Portugal, 4% in Northern Portugal, 2.9% in Istanbul and 4.3% among Turkish Cypriots. E1b1a is closely related to E1b1b, the most frequent clade in Europe. E lineages that are not E1b1a or E1b1b could therefore reflect either a recent expansion associated with E1b1a or ancient population movements associated with E1b1b. For example haplogroup E1a
lineages have been detected in Portugal (5/553 = 1%), among Italians in Calabria (1/80=1.3%) and among Albanians in Calabria (2/68=2.9%). According to a study by , The distribution of Haplogroup E1a lineages in Portugal was independent of the distribution of the younger and more ubiquitous E1b1a. The authors suggest that this distribution is consistent with a prehistoric migration from Africa to Iberia, possibly alongside mtDNA haplogroup U6.
Haplogroups A and B are thought to have been the predominant haplogroups in Central and Southern Africa prior to the Bantu Expansion. Currently these haplogroups are less common than E lineages. In a sample of 5,000 African men, haplogroup A had a frequency of 5%. Haplogroup A has rare occurrences in Europe but recently the haplogroup was detected in seven males with the same surname who were in Britain.
lineages are relatively infrequent (1% or less) throughout Europe with the exception of Iberia
where frequencies as high as 22% have been reported and some regions of Italy
where frequencies as high as 2 to 3% have been found.
In Iberia
the mean frequency of Haplogroup L lineages reaches 3.83% and the frequency is higher in Portugal
(5.83%) than in Spain
(2.9% average) and without parallel in the rest of Europe. In both countries frequencies vary widely between regions with increase frequencies observed for Madeira (Portugal), Southern Portugal, Cordoba (Southern Spain) and North Western Castile (Spain). In the Autonomous regions of Portugal
, L haplogroups constituted about 13% of the lineages in Madeira
, significantly more than in the Azores
.. In the Spanish archipelago of Canary Islands
, frequencies have been reported at 6.6%. Regarding Iberia, current debates are concerned with whether these lineages are associated with prehistoric migrations, the Islamic occupation of Iberia or the slave trade. suggested that African lineages in Iberia were predominantly the result of Atlantic Slave Trade. revealed that most of the L lineages in Iberia matched Northwest African L lineages rather than contemporary Sub-Saharan L lineages. The authors suggest this pattern indicates that most of the Sub-Saharan L lineages entered Iberia in prehistoric times rather than during the slave trade. According to , the sub-Saharan lineages found in Iberia matched lineages from diverse regions in Africa. They suggest this pattern is more compatible with recent arrival of these lineages after slave trading began in the 15th century. According to the study, alternative scenarios that invoke much older and demographically more significant introductions or that claim a substantial role of the Roman and/or Islamic periods on the introduction of sub-Saharan lineages seem unlikely. extracted DNA from human remains that were exhumed from old burial sites in Al-Andalus
, Spain. The remains date to between 12th-13th century. The frequency of Sub-Saharan lineages detected in the medieval samples was 14.6% and 8.3% in the present population of Priego de Cordoba
. The authors suggest the Muslim occupation
and prehistoric migrations before the Muslim occupation would have been the source of these lineages. The highest frequencies of Sub-Saharan lineages found so far in Europe were observed by Alvarez et al. 2010 in the comarca
of Sayago
(18.2%) which is according to the authors "comparable to that described for the South of Portugal" and by Pereira et al. 2010 in Alcacer do Sal (22%).
In Italy
, Haplogroup L lineages are present at lower frequencies than Iberia, and only detected in certain regions, such as between 2 and 3% in Latium
, Tuscany
, Basilicata
and Sicily
.
In Eastern Europe, Haplogroup L lineages are present at very low frequencies. Though a high diversity of African mtDNA lineages have been detected, few lineages have accumulated enough mutations in Europe to form monophyletic clusters. detected only two monophyletic clusters, L1b and L3b in Russians with an estimated age no greater than 6,500 years. identified African L1b, L2a, L3b, L3d and M1 clades in Slavic populations at low frequencies. L1b, L3b and L3d had matches with West African populations, indicating that these lineages probably entered Europe through Iberia. One lineage L2a1a, appeared to be much older, indicating that it may have entered Europe in prehistoric times. This clade was possibly related to L2a1 clades identified in ten individuals of Ashkenazi heritage from France, Germany, Poland, Romania and Russia. L2a lineages are widespread throughout Africa, as a result the origins of this lineage are uncertain.
Haplogroup M1 is also found in Europe at low frequencies. In a study by Gonzalez et al. 2007, haplogroup M1 had a frequency of 0.3%. The highest frequencies were found in Sicily
where 3.8% of the population were members of haplogroup M1. The origins of haplogroup M1 have yet to be conclusively established. One clade of haplgroup M1, M1a is widely accepted to be of East African origin. About 40% of all clades of M1 found in Europe are M1a and consequently of recent East African origin.
, 1.9 % in Greece
and 1.5% in Tuscany
. According to the authors, this is consistent in the case of Spain, with the historically known movement of individuals of North African ancestry into Iberia, although it is possible that this estimate also reflects a wider range of mixture times. Another study by the same author in 2011 that analyzed genome-wide polymorphism data from about 40 West Eurasian groups showed that "almost all Southern Europeans have inherited 1%–3% African ancestry with an average mixture date of around 55 generations ago, consistent with North African gene flow at the end of the Roman Empire and subsequent Arab migrations". According to the authors, application of f4 Ancestry Estimation, a method which produces accurate estimates of ancestry proportions, even in the absence of data from the true ancestral populations, suggests that the "highest proportion of African ancestry in Europe is in Iberia (Portugal 3.2±0.3% and Spain 2.4±0.3%), consistent with inferences based on mitochondrial DNA and Y chromosomes and the observation by Auton et al. that within Europe, the Southwestern Europeans have the highest haplotype-sharing with Africans". The authors found the following West African admixture proportions in Europe using f4 Ancestry Estimation :
, this or component haplotypes reaches a peak frequency in Sardinia with components of ~20%. Three independent studies conclude this haplotype is paleo North African in origin. Several HLA haplotypes and alleles that appear to be of recent Africa origin are found in Europe with frequencies declining from SW to north east similar to A30-B18-DR3.
A number of other alleles including, Cw*0501, Cw*0701 and Cw*1601 appear restricted to European and African populations. This pattern has been described as being suggestive of a close historical relationship between Europeans and Africans.
, in the Aran valley in the Pyrenees
and the large islands of Sicily
(ranging from 1.56% at Valledolmo to 5.5% at Alia), Corsica
and Sardinia
. According to Calderon et al. 2007, although some researchers have associated African traces in Iberia to Islamic invasions, the presence of GM*1,17 23' 5* haplotype in Iberia may in fact be due to more ancient processes as well as more recent ones through the introduction of genes from black slaves from Africa.
is associated with resistance to malaria
. Individuals with one copy of the sickle cell gene, heterozygotes, have higher resistance to malaria than individuals with no sickle cell genes. In regions affected by malaria, the fertility of sickle cell heterozygotes will be higher than average. Individuals with two copies of the sickle cell gene, homozygotes, will be affected by sickle cell disease and historically have had lower than average fertility. The sickle cell trait is thus an example of heterozygote advantage
which is subject to balancing selection
. When the sickle cell trait is introduced into a region affected by malaria, balancing selection will on one hand act to increase the frequency of the trait to counter malaria. On the other hand if the frequency of the trait in the population becomes high enough so that homozygotes with sickle cell disease become common, balancing selection will act to limit the spread of the trait. Therefore in regions affected by malaria, the sickle cell trait is maintained at intermediate frequencies relative to the incidence of malaria.
In Africa, malaria is believed to be one of the most important factors that contributed to restricting population growth in prehistoric times. Sickle cell mutations are believed to have occurred independently at least five times. Four variants are of African origin and one of Indian/Arabian origin. The African variants are referred to as Cameroon, Senegal, Benin and Bantu. The emergence of the sickle cell trait would have contributed to population expansion, with the emergence of farming into tropical regions where malaria was endemic.
Archeological and historical evidence suggest that the malaria had been endemic in the
Mediterranean regions of Europe in historical times. In Eastern Mediterranean regions, such as Italy, Greece, Albania and Turkey the Benin haplotype is the most frequent sickle cell variant. The Benin haplotype is also the most frequent variant in the Middle East and has been observed in Syrians, Palestinians, Israeli Arabs, Israeli Jews and Western Saudi Arabians. This suggests that the Benin haplotype may have expanded from West Africa into North Africa and then into the Middle East and Europe. The spread of the Benin haplotype to the Mediterranean region has been associated with various events including Late Stone Age expansions from West Africa into North Africa, the trans-Saharan trade
and the Arab Slave Trade
. The occurrence of sickle cell trait is particularly high in Sicily
where frequencies of 13% have been reported. In New York City, Sicilian Americans are second to African Americans in occurrence of Sickle cell disease. The high frequencies of the trait have been associated with the Arab invasion of Sicily in the 7th Century during which Sudanese soldiers were recruited by the Caliphate. Portugal is the only region in Europe where the Senegal and Bantu haplotypes are frequent. These may be associated with Portuguese naval exploits, including the Atlantic Slave Trade
and the colonization of various African countries.
In Europe
, the highest prevalence of the disease has been observed in France
as a result of population growth in African-Caribbean regions of overseas France
, and now immigration essentially from North
and sub-Saharan Africa
to mainland France. SCD has become the most common genetic disease in this country. In 2007, 28.45% of all newborns in mainland France in 2007 had at least one parent originated from a region defined "at risk" (mainly Africa and Overseas departments and territories of France) and were screened for SCD. The Paris metropolitan district (Île-de-France
) is the region that accounts for the largest number of at-risk. Indeed, nearly 56% of all newborns in this area in 2007 had at least one parent originated from a region defined as "at-risk" and were screened for SCD. The second largest number of at-risk is in Provence-Alpes-Côte d'Azur
at nearly 42% and the lowest number is in Brittany
at 4.40%.
which existed about 12,000 years ago in Palestine, has been the subject of various archeological investigations as the Natufian culture is generally believed to be the source of the European and North African Neolithic.
According to a hypothesis stated by , Natufian culture
emerged from the mixing of two stone age cultures: (1) the Kebaran
, a culture indigenous to the Levant and (2) the Mushabian
, a culture introduced into the Levant from North Africa. This Mushabian culture is suggested to have originated in Africa as archeological sites with Mushabian industries in the Nile Valley predate those in the Levant. The Mushabians would have then moved into the Sinai from the Nile Delta bringing with them their technologies. states: "the population overflow from Northeast Africa played a definite role in the establishment of the Natufian adaptation, which in turn led to the emergence of agriculture as a new subsistence system".
A study by analysed human remains from the Natufian culture.
According to the study, there is evidence of Sub-Saharan influences in the Natufian samples. They argue that these influences would have been diluted by the interbreeding of the Neolithic farmers from the Near East with the indigenous foragers in Europe. associate the Sub-Saharan influences detected in the Natufian samples with the migration of E1b1b lineages from East Africa to the Levant and then into Europe.
Human
Humans are the only living species in the Homo genus...
genetic
Genetics
Genetics , a discipline of biology, is the science of genes, heredity, and variation in living organisms....
polymorphisms
Polymorphism (biology)
Polymorphism in biology occurs when two or more clearly different phenotypes exist in the same population of a species — in other words, the occurrence of more than one form or morph...
, which are considered to be evidence for movements of people from Africa to Eurasia in both the prehistoric and historic past.
Geographical influences
The Mediterranean SeaMediterranean Sea
The Mediterranean Sea is a sea connected to the Atlantic Ocean surrounded by the Mediterranean region and almost completely enclosed by land: on the north by Anatolia and Europe, on the south by North Africa, and on the east by the Levant...
and the Sahara Desert were formidable barriers to gene flow between Sub-Saharan Africa and Europe. But Europe and the Mediterranean were periodically more easily accessible to Africans due to fluctuations in the size and climate of the Sahara. At the Strait of Gibraltar
Strait of Gibraltar
The Strait of Gibraltar is a narrow strait that connects the Atlantic Ocean to the Mediterranean Sea and separates Spain in Europe from Morocco in Africa. The name comes from Gibraltar, which in turn originates from the Arabic Jebel Tariq , albeit the Arab name for the Strait is Bab el-Zakat or...
, Africa and Europe are separated by only 15 kilometres (9.3 mi) of water. At the Suez
Suez
Suez is a seaport city in north-eastern Egypt, located on the north coast of the Gulf of Suez , near the southern terminus of the Suez Canal, having the same boundaries as Suez governorate. It has three harbors, Adabya, Ain Sokhna and Port Tawfiq, and extensive port facilities...
, Eurasia
Eurasia
Eurasia is a continent or supercontinent comprising the traditional continents of Europe and Asia ; covering about 52,990,000 km2 or about 10.6% of the Earth's surface located primarily in the eastern and northern hemispheres...
is connected to Africa forming a single land mass. The Nile river valley, which runs from East Africa
East Africa
East Africa or Eastern Africa is the easterly region of the African continent, variably defined by geography or geopolitics. In the UN scheme of geographic regions, 19 territories constitute Eastern Africa:...
to the Mediterranean Sea could have served as a bidirectional corridor in the Sahara desert, that allows communication between Sub-Saharan Africa with the peoples of Eurasia.
First settlers
According to the leading theory of human origins, known as the Out of Africa theory, anatomically modern humansAnatomically modern humans
The term anatomically modern humans in paleoanthropology refers to early individuals of Homo sapiens with an appearance consistent with the range of phenotypes in modern humans....
first emerged in Africa 150,000-200,000 years ago. All non-Africans are descended from at least one group of humans who migrated out of Africa into western Asia 50,000-70,000 years ago. The first modern humans in Europe, the Cro-Magnon
Cro-Magnon
The Cro-Magnon were the first early modern humans of the European Upper Paleolithic. The earliest known remains of Cro-Magnon-like humans are radiometrically dated to 35,000 years before present....
, arrived from Western Asia and are believed to have completely replaced the previous inhabitants, the Neanderthal
Neanderthal
The Neanderthal is an extinct member of the Homo genus known from Pleistocene specimens found in Europe and parts of western and central Asia...
s. Cro-Magnons were in the Middle East (Lebanon) by 45,000 years ago and in Eastern Europe by 40,000 years ago. By 30,000 years ago, the Cro-Magnon people had populated much of Europe. This was however not the last major human migration into Europe and this paleolithic population was to some extent replaced by later migrations to be discussed below.
Duration within refuges
During the Last Glacial MaximumLast Glacial Maximum
The Last Glacial Maximum refers to a period in the Earth's climate history when ice sheets were at their maximum extension, between 26,500 and 19,000–20,000 years ago, marking the peak of the last glacial period. During this time, vast ice sheets covered much of North America, northern Europe and...
, a period between 25,000 and 19,000 years ago, large ice sheets over a kilometer thick covered much of Northern Europe, making the region uninhabitable to humans. It is believed that human populations retreated south to warmer regions near the Mediterranean. Refuges during this period are believed to have been in Iberia
Iberian Peninsula
The Iberian Peninsula , sometimes called Iberia, is located in the extreme southwest of Europe and includes the modern-day sovereign states of Spain, Portugal and Andorra, as well as the British Overseas Territory of Gibraltar...
, the Balkans
Balkans
The Balkans is a geopolitical and cultural region of southeastern Europe...
and Italy
Italian Peninsula
The Italian Peninsula or Apennine Peninsula is one of the three large peninsulas of Southern Europe , spanning from the Po Valley in the north to the central Mediterranean Sea in the south. The peninsula's shape gives it the nickname Lo Stivale...
.
DNA evidence suggests that during the Last Glacial Maximum, there was some gene flow
Gene flow
In population genetics, gene flow is the transfer of alleles of genes from one population to another.Migration into or out of a population may be responsible for a marked change in allele frequencies...
from Africa into Iberia. After the Last Glacial Maximum, when the European climate warmed up, the refuges are thought to have been the source from which Europe was repopulated. African lineages that had been introduced into the Iberian refuge would have then dispersed all over Europe with the Northward expansion of humans. This could explain the presence of genetic lineages in Eastern Europe and as far North as Russia, that appear to have prehistoric links to Northwest and West Africa (see mtDNA). The expansion of human populations from Iberian refuges is also believed to have moved back to Northwest Africa.
Neolithic to the end of the prehistoric
The change from hunting and gatheringHunter-gatherer
A hunter-gatherer or forage society is one in which most or all food is obtained from wild plants and animals, in contrast to agricultural societies which rely mainly on domesticated species. Hunting and gathering was the ancestral subsistence mode of Homo, and all modern humans were...
to agriculture during the Neolithic Revolution
Neolithic Revolution
The Neolithic Revolution was the first agricultural revolution. It was the transition from hunting and gathering to agriculture and settlement. Archaeological data indicates that various forms of plants and animal domestication evolved independently in 6 separate locations worldwide circa...
was a watershed in world history. The societies that first made the change to agriculture are believed to have lived in the Middle East around 10,000 BCE. Agriculture was introduced into Europe by migrating farmers from the Middle East. According to the demic diffusion
Demic diffusion
Demic diffusion is a demographic term referring to a migratory model developed by Cavalli-Sforza, that consists of population diffusion into and across an area previously uninhabited by that group, possibly, but not necessarily, displacing, replacing, or intermixing with a pre-existing population...
model, these Middle Eastern farmers either replaced or interbred with the local hunter-gather populations that had been living in Europe since the "out of Africa" migration.
It has been suggested that the first Middle Eastern farmers had African influences. There have been suggestions that some genetic lineages found in the Middle East arrived there during this period. The first Agricultural societies in the Middle East are generally thought to have emerged out of the Natufian Culture
Natufian culture
The Natufian culture was a Mesolithic culture that existed from 12,500 to 9,500 BC in the Levant, a region in the Eastern Mediterranean. It was unusual in that it was sedentary, or semi-sedentary, before the introduction of agriculture...
, which existed in Palestine from 12,000 BCE-10,000 BCE. An important migration from Africa across the Sinai appears to have occurred before the formation of the Natufian.
Historic period
In historical times, there has been a well-documented period of North African influence in Southern Europe, especially IberiaIberian Peninsula
The Iberian Peninsula , sometimes called Iberia, is located in the extreme southwest of Europe and includes the modern-day sovereign states of Spain, Portugal and Andorra, as well as the British Overseas Territory of Gibraltar...
and Sicily
Sicily
Sicily is a region of Italy, and is the largest island in the Mediterranean Sea. Along with the surrounding minor islands, it constitutes an autonomous region of Italy, the Regione Autonoma Siciliana Sicily has a rich and unique culture, especially with regard to the arts, music, literature,...
during the time of the Islamic Golden Age
Islamic Golden Age
During the Islamic Golden Age philosophers, scientists and engineers of the Islamic world contributed enormously to technology and culture, both by preserving earlier traditions and by adding their own inventions and innovations...
. The genetic effect of this period on modern European populations is the subject of discussion (see below). In more recent history, the peoples of Europe and Africa came into contact during the exploration
European exploration of Africa
European exploration of Africa began with Ancient Greeks and Romans, who explored and established settlements in North Africa. Fifteenth Century Portugal, especially under Henry the Navigator probed along the West African coast. Scientific curiosity and Christian missionary spirit soon were...
and colonisation of Africa
Colonisation of Africa
The colonisation of Africa has a long history, the most famous phase being the European Scramble for Africa during the late 19th and early 20th century.- Ancient colonialism :...
and as a consequence of the Atlantic slave trade
Atlantic slave trade
The Atlantic slave trade, also known as the trans-atlantic slave trade, refers to the trade in slaves that took place across the Atlantic ocean from the sixteenth through to the nineteenth centuries...
. As a result of these recent contacts, lineages of African descent have also been detected in Europe. In general, African admixture is distributed along a South-to-North cline, with peaks in the Mediterranean region and Iberia.
Assessing African genetic contributions in non-Africans
The evolutionary forces that contribute to patterns of human genetic variation include new mutations, natural selectionNatural selection
Natural selection is the nonrandom process by which biologic traits become either more or less common in a population as a function of differential reproduction of their bearers. It is a key mechanism of evolution....
, sexual selection
Sexual selection
Sexual selection, a concept introduced by Charles Darwin in his 1859 book On the Origin of Species, is a significant element of his theory of natural selection...
, genetic drift
Genetic drift
Genetic drift or allelic drift is the change in the frequency of a gene variant in a population due to random sampling.The alleles in the offspring are a sample of those in the parents, and chance has a role in determining whether a given individual survives and reproduces...
, population bottleneck
Population bottleneck
A population bottleneck is an evolutionary event in which a significant percentage of a population or species is killed or otherwise prevented from reproducing....
s, founder effects, isolation by distance
Isolation by distance
Isolation by distance describes the tendency of individuals to find mates from nearby populations rather than distant populations. As a result of this tendency, populations that live near each other are genetically more similar than populations that live further apart. Isolation by distance results...
, genetic admixture
Genetic admixture
Genetic admixture occurs when individuals from two or more previously separated populations begin interbreeding. Admixture results in the introduction of new genetic lineages into a population. It has been known to slow local adaptation by introducing foreign, unadapted genotypes...
and barriers to gene flow
Gene flow
In population genetics, gene flow is the transfer of alleles of genes from one population to another.Migration into or out of a population may be responsible for a marked change in allele frequencies...
. The most influential factors affecting human genetic variation are founder effects and isolation by distance
Isolation by distance
Isolation by distance describes the tendency of individuals to find mates from nearby populations rather than distant populations. As a result of this tendency, populations that live near each other are genetically more similar than populations that live further apart. Isolation by distance results...
.
Founder effect
Founder effect
In population genetics, the founder effect is the loss of genetic variation that occurs when a new population is established by a very small number of individuals from a larger population. It was first fully outlined by Ernst Mayr in 1942, using existing theoretical work by those such as Sewall...
occurs when a population is established by a small number of individuals who have departed from a much larger population. Several generations after the population has expanded, individuals will still possess the limited gene pool of the founders. Therefore founder effects result in a loss of genetic diversity
Genetic diversity
Genetic diversity, the level of biodiversity, refers to the total number of genetic characteristics in the genetic makeup of a species. It is distinguished from genetic variability, which describes the tendency of genetic characteristics to vary....
. Genetic evidence suggests that the out of Africa migration involved only small number of individuals. The African migrants carried a small subset of the prehistoric African genetic diversity, resulting in a founder effect of the Non-African population. As humans spread across the globe populating Eurasia, Australia and the Americas, there were several founder effects. As a result of these serial founder effects, genetic diversity tends to decrease with distance from Africa.
The other big factor contributing to patterns of human genetic variation is "Isolation by distance
Isolation by distance
Isolation by distance describes the tendency of individuals to find mates from nearby populations rather than distant populations. As a result of this tendency, populations that live near each other are genetically more similar than populations that live further apart. Isolation by distance results...
". According to this model populations that live near each other are more likely to exchange mates than populations that live further apart. As a result populations that live near each other are genetically more similar than populations that live far apart.
| Africa | Oceania | East Asia | Europe | |
| Oceania | 24.7 | |||
| East Asia | 20.6 | 10 | ||
| Europe | 16.6 | 13.5 | 9.7 | |
| America | 22.6 | 14.6 | 8.9 | 9.5 |
Genetic distance
Genetic distance
Genetic distance refers to the genetic divergence between species or between populations within a species. It is measured by a variety of parameters. Smaller genetic distances indicate a close genetic relationship whereas large genetic distances indicate a more distant genetic relationship...
is a measure used to compare the genetic relationship between populations. It is based on the principle that populations that share similar frequencies of a trait are closer relations than populations that have different frequencies of a trait. The genetic distance between two populations increases linearly with the geographic distance between the two populations due to isolation by distance
Isolation by distance
Isolation by distance describes the tendency of individuals to find mates from nearby populations rather than distant populations. As a result of this tendency, populations that live near each other are genetically more similar than populations that live further apart. Isolation by distance results...
and serial founder effects.Genetic admixture
Genetic admixture
Genetic admixture occurs when individuals from two or more previously separated populations begin interbreeding. Admixture results in the introduction of new genetic lineages into a population. It has been known to slow local adaptation by introducing foreign, unadapted genotypes...
increases the genetic diversity of a population. When admixture occurs between populations, the genetic distance between the two populations is reduced.
applied genetic distance measures to various populations around the world to infer phylogenetic relationships (see Table on the right). All non-African populations are more closely related to each other (i.e. short genetic distance) than they are to African populations. This is consistent with a founder effect of the non-African population in that only a few individuals participated in the initial out of Africa migration. The largest genetic distances observed are between Africa and Oceania and between Africa and the Americas. This is consistent with the isolation by distance and serial founder effects.
suggests that the genetic distance between Sub-Saharan Africa and Europe is anomalously lower than it should be if the two populations have been evolving independently. The study suggests that the lower genetic distance between Europe and Africa can be explained by genetic admixture.
Defining African admixture
Generally lineages used to characterize African admixture are those that are specific to Africa. Some DNA polymorphisms are shared by Europeans, West Asians, North AfricaNorth Africa
North Africa or Northern Africa is the northernmost region of the African continent, linked by the Sahara to Sub-Saharan Africa. Geopolitically, the United Nations definition of Northern Africa includes eight countries or territories; Algeria, Egypt, Libya, Morocco, South Sudan, Sudan, Tunisia, and...
ns and Sub-Saharan Africa
Sub-Saharan Africa
Sub-Saharan Africa as a geographical term refers to the area of the African continent which lies south of the Sahara. A political definition of Sub-Saharan Africa, instead, covers all African countries which are fully or partially located south of the Sahara...
ns. Examples of such variants include the y-chromosomal
Y chromosome
The Y chromosome is one of the two sex-determining chromosomes in most mammals, including humans. In mammals, it contains the gene SRY, which triggers testis development if present. The human Y chromosome is composed of about 60 million base pairs...
haplogroup E1b1b and mitochondrial haplogroup M1.
This sharing of polymorphisms is the result of long distance movements of peoples between Sub-Saharan Africa and Eurasia that involved traversing North Africa and sometimes the Middle East. Consequently the definitions of "African", "Sub-Saharan African" and "North African" will depend on the time frame of reference or the semantic preferences of any particular scientist. Due to prehistoric migrations in and out of Africa, North African populations tend to exhibit allele
Allele
An allele is one of two or more forms of a gene or a genetic locus . "Allel" is an abbreviation of allelomorph. Sometimes, different alleles can result in different observable phenotypic traits, such as different pigmentation...
frequencies that are intermediate between Sub-Saharan Africa and Eurasia
Eurasia
Eurasia is a continent or supercontinent comprising the traditional continents of Europe and Asia ; covering about 52,990,000 km2 or about 10.6% of the Earth's surface located primarily in the eastern and northern hemispheres...
. Due to this complex genetic profile of Africa, African admixture in Europe could be the result of direct contact with Sub-Saharan Africans or indirectly through contact with North Africans with Sub-Saharan affiliations.
In some cases, lineages found in Africa and Europe may have a common origin in Asia
Asia
Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...
(for example Y haplogroups R1
Haplogroup R1 (Y-DNA)
In human genetics, Haplogroup R1 is a Y-chromosome DNA haplogroup, a subgroup of haplogroup R, associated with the M173 mutation. It is dominated in practice by two very common Eurasian clades, R1a and R1b, which together are found all over Eurasia except in Southeast Asia and East Asia...
, T
Haplogroup T (Y-DNA)
In human genetics, Haplogroup T is a human Y-chromosome DNA haplogroup. From 2002 to 2008, it was known as Haplogroup K2. It should not be confused with the mitochondrial DNA haplogroup T, of the same name....
) and Haplogroup U. One clade of haplogroup U, U6a1 is known to have expanded from North and East Africa back into Europe . Other lineages are known to have moved from Europe directly into Africa (for example mitochondrial haplogroups H1, H3. Such back migrations between Africa and Eurasia also complicate defining admixture.
Y-DNA
One proposed example of HoloceneHolocene
The Holocene is a geological epoch which began at the end of the Pleistocene and continues to the present. The Holocene is part of the Quaternary period. Its name comes from the Greek words and , meaning "entirely recent"...
gene flow from Africa to Europe, via the Middle East, is thought to be E1b1b1, which is thought to have emerged about 22,000 years ago in East Africa
East Africa
East Africa or Eastern Africa is the easterly region of the African continent, variably defined by geography or geopolitics. In the UN scheme of geographic regions, 19 territories constitute Eastern Africa:...
and branches of it are thought to have migrated to the Middle East
Middle East
The Middle East is a region that encompasses Western Asia and Northern Africa. It is often used as a synonym for Near East, in opposition to Far East...
by 11,000 years ago during the late Pleistocene
Pleistocene
The Pleistocene is the epoch from 2,588,000 to 11,700 years BP that spans the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek and ....
or early Neolithic
Neolithic
The Neolithic Age, Era, or Period, or New Stone Age, was a period in the development of human technology, beginning about 9500 BC in some parts of the Middle East, and later in other parts of the world. It is traditionally considered as the last part of the Stone Age...
periods.
Entering the late mesolithic
Mesolithic
The Mesolithic is an archaeological concept used to refer to certain groups of archaeological cultures defined as falling between the Paleolithic and the Neolithic....
Natufian culture, the E1b1b1a2 (E-V13) sub-clade has been associated with the spread of farming from the Middle East into Europe either during or just before the Neolithic transition. E1b1b1 lineages are found throughout Europe but are distributed along a South-to-North cline, with a E1b1b1a mode
Mode (statistics)
In statistics, the mode is the value that occurs most frequently in a data set or a probability distribution. In some fields, notably education, sample data are often called scores, and the sample mode is known as the modal score....
in the Balkans
Balkans
The Balkans is a geopolitical and cultural region of southeastern Europe...
.
In separate migrations, E lineages in the form of the E1b1b1b subclade appear to have entered Europe from Northwest Africa into Iberia. In a sample of European males, Cruciani et al. observed Haplogroup E at a frequencies of 7.2%. The timing of this movement has been given widely variant estimates.
A big expansion of peoples throughout Sub-Saharan Africa occurred after the introduction of agriculture 5,000 years ago. During the Bantu expansion
Bantu expansion
The Bantu expansion or the Bantu Migration was a millennia-long series of migrations of speakers of the original proto-Bantu language group...
people carrying Haplogroup E
Haplogroup E (Y-DNA)
In human genetics, Haplogroup E is a human Y-chromosome DNA haplogroup. Haplogroup E is one of the two main branches of the older Haplogroup DE, the other main branch being haplogroup D. The E clade is divided into two subclades: E1 and E2 .-Origins:Underhill et al. proposed that haplogroup E...
(not including E1b1b) lineages dispersed across much of Sub-Saharan Africa from their homeland near the border between Nigeria and Cameroon. The haplogroup most often associated with this expansion is E1b1a, which constitutes up to 48% of the African male gene pool. The presence of E1b1a lineages outside Africa can typically be associated with events that occurred after the Bantu Expansion, such as the trade in African slaves or the Moorish
Moors
The description Moors has referred to several historic and modern populations of the Maghreb region who are predominately of Berber and Arab descent. They came to conquer and rule the Iberian Peninsula for nearly 800 years. At that time they were Muslim, although earlier the people had followed...
occupation of Iberia
Al-Andalus
Al-Andalus was the Arabic name given to a nation and territorial region also commonly referred to as Moorish Iberia. The name describes parts of the Iberian Peninsula and Septimania governed by Muslims , at various times in the period between 711 and 1492, although the territorial boundaries...
. In much of Europe frequencies of E lineages which are not E1b1b are very low, usually less than 1%. For example Cruciani et al. 2004, report such lineages at 2% in Southern Portugal, 4% in Northern Portugal, 2.9% in Istanbul and 4.3% among Turkish Cypriots. E1b1a is closely related to E1b1b, the most frequent clade in Europe. E lineages that are not E1b1a or E1b1b could therefore reflect either a recent expansion associated with E1b1a or ancient population movements associated with E1b1b. For example haplogroup E1a
Haplogroup E1a (Y-DNA)
In human genetics, Haplogroup E1a is a human Y-chromosome DNA haplogroup. Haplogroup E1a, along with haplogroup E1b, is one of the two main branches of the older E1. The E1a clade is divided into several subclades.- Distribution :...
lineages have been detected in Portugal (5/553 = 1%), among Italians in Calabria (1/80=1.3%) and among Albanians in Calabria (2/68=2.9%). According to a study by , The distribution of Haplogroup E1a lineages in Portugal was independent of the distribution of the younger and more ubiquitous E1b1a. The authors suggest that this distribution is consistent with a prehistoric migration from Africa to Iberia, possibly alongside mtDNA haplogroup U6.
Haplogroups A and B are thought to have been the predominant haplogroups in Central and Southern Africa prior to the Bantu Expansion. Currently these haplogroups are less common than E lineages. In a sample of 5,000 African men, haplogroup A had a frequency of 5%. Haplogroup A has rare occurrences in Europe but recently the haplogroup was detected in seven males with the same surname who were in Britain.
mtDNA
Haplogroup LMacro-haplogroup L (mtDNA)
In human mitochondrial genetics, L is the mitochondrial DNA macro-haplogroup that is at the root of the human mtDNA phylogenetic tree. As such, it represents the most ancestral mitochondrial lineage of all currently living modern humans....
lineages are relatively infrequent (1% or less) throughout Europe with the exception of Iberia
Iberia
The name Iberia refers to three historical regions of the old world:* Iberian Peninsula, in Southwest Europe, location of modern-day Portugal and Spain** Prehistoric Iberia...
where frequencies as high as 22% have been reported and some regions of Italy
Italy
Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...
where frequencies as high as 2 to 3% have been found.
In Iberia
Iberia
The name Iberia refers to three historical regions of the old world:* Iberian Peninsula, in Southwest Europe, location of modern-day Portugal and Spain** Prehistoric Iberia...
the mean frequency of Haplogroup L lineages reaches 3.83% and the frequency is higher in Portugal
Portugal
Portugal , officially the Portuguese Republic is a country situated in southwestern Europe on the Iberian Peninsula. Portugal is the westernmost country of Europe, and is bordered by the Atlantic Ocean to the West and South and by Spain to the North and East. The Atlantic archipelagos of the...
(5.83%) than in Spain
Spain
Spain , officially the Kingdom of Spain languages]] under the European Charter for Regional or Minority Languages. In each of these, Spain's official name is as follows:;;;;;;), is a country and member state of the European Union located in southwestern Europe on the Iberian Peninsula...
(2.9% average) and without parallel in the rest of Europe. In both countries frequencies vary widely between regions with increase frequencies observed for Madeira (Portugal), Southern Portugal, Cordoba (Southern Spain) and North Western Castile (Spain). In the Autonomous regions of Portugal
Autonomous regions of Portugal
The two Autonomous Regions of Portugal are the Azores and Madeira...
, L haplogroups constituted about 13% of the lineages in Madeira
Madeira
Madeira is a Portuguese archipelago that lies between and , just under 400 km north of Tenerife, Canary Islands, in the north Atlantic Ocean and an outermost region of the European Union...
, significantly more than in the Azores
Azores
The Archipelago of the Azores is composed of nine volcanic islands situated in the middle of the North Atlantic Ocean, and is located about west from Lisbon and about east from the east coast of North America. The islands, and their economic exclusion zone, form the Autonomous Region of the...
.. In the Spanish archipelago of Canary Islands
Canary Islands
The Canary Islands , also known as the Canaries , is a Spanish archipelago located just off the northwest coast of mainland Africa, 100 km west of the border between Morocco and the Western Sahara. The Canaries are a Spanish autonomous community and an outermost region of the European Union...
, frequencies have been reported at 6.6%. Regarding Iberia, current debates are concerned with whether these lineages are associated with prehistoric migrations, the Islamic occupation of Iberia or the slave trade. suggested that African lineages in Iberia were predominantly the result of Atlantic Slave Trade. revealed that most of the L lineages in Iberia matched Northwest African L lineages rather than contemporary Sub-Saharan L lineages. The authors suggest this pattern indicates that most of the Sub-Saharan L lineages entered Iberia in prehistoric times rather than during the slave trade. According to , the sub-Saharan lineages found in Iberia matched lineages from diverse regions in Africa. They suggest this pattern is more compatible with recent arrival of these lineages after slave trading began in the 15th century. According to the study, alternative scenarios that invoke much older and demographically more significant introductions or that claim a substantial role of the Roman and/or Islamic periods on the introduction of sub-Saharan lineages seem unlikely. extracted DNA from human remains that were exhumed from old burial sites in Al-Andalus
Al-Andalus
Al-Andalus was the Arabic name given to a nation and territorial region also commonly referred to as Moorish Iberia. The name describes parts of the Iberian Peninsula and Septimania governed by Muslims , at various times in the period between 711 and 1492, although the territorial boundaries...
, Spain. The remains date to between 12th-13th century. The frequency of Sub-Saharan lineages detected in the medieval samples was 14.6% and 8.3% in the present population of Priego de Cordoba
Priego de Córdoba
Priego de Córdoba is a town and municipality of southern Spain in the extreme southeastern portion of the province of Córdoba, near the headwater of the Guadajoz River, and on the northern slope of the Sierra de Priego. The population in 2008 was 22,558....
. The authors suggest the Muslim occupation
Umayyad conquest of Hispania
The Umayyad conquest of Hispania is the initial Islamic Ummayad Caliphate's conquest, between 711 and 718, of the Christian Visigothic Kingdom of Hispania, centered in the Iberian Peninsula, which was known to them under the Arabic name al-Andalus....
and prehistoric migrations before the Muslim occupation would have been the source of these lineages. The highest frequencies of Sub-Saharan lineages found so far in Europe were observed by Alvarez et al. 2010 in the comarca
Comarca
A comarca is a traditional region or local administrative division found in parts of Spain, Portugal, Panama, Nicaragua, and Brazil. The term is derived from the term marca, meaning a "march, mark", plus the prefix co- meaning "together, jointly".The comarca is known in Aragonese as redolada and...
of Sayago
Sayago
Sayago is a comarca in the province of Zamora, central Spain.- Geography :The comarca is located at the southwest of the Zamora province. The main geographical characteristic is the isolation caused by the Duero and Tormes rivers canyons...
(18.2%) which is according to the authors "comparable to that described for the South of Portugal" and by Pereira et al. 2010 in Alcacer do Sal (22%).
In Italy
Italy
Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...
, Haplogroup L lineages are present at lower frequencies than Iberia, and only detected in certain regions, such as between 2 and 3% in Latium
Latium
Lazio is one of the 20 administrative regions of Italy, situated in the central peninsular section of the country. With about 5.7 million residents and a GDP of more than 170 billion euros, Lazio is the third most populated and the second richest region of Italy...
, Tuscany
Tuscany
Tuscany is a region in Italy. It has an area of about 23,000 square kilometres and a population of about 3.75 million inhabitants. The regional capital is Florence ....
, Basilicata
Basilicata
Basilicata , also known as Lucania, is a region in the south of Italy, bordering on Campania to the west, Apulia to the north and east, and Calabria to the south, having one short southwestern coastline on the Tyrrhenian Sea between Campania in the northwest and Calabria in the southwest, and a...
and Sicily
Sicily
Sicily is a region of Italy, and is the largest island in the Mediterranean Sea. Along with the surrounding minor islands, it constitutes an autonomous region of Italy, the Regione Autonoma Siciliana Sicily has a rich and unique culture, especially with regard to the arts, music, literature,...
.
In Eastern Europe, Haplogroup L lineages are present at very low frequencies. Though a high diversity of African mtDNA lineages have been detected, few lineages have accumulated enough mutations in Europe to form monophyletic clusters. detected only two monophyletic clusters, L1b and L3b in Russians with an estimated age no greater than 6,500 years. identified African L1b, L2a, L3b, L3d and M1 clades in Slavic populations at low frequencies. L1b, L3b and L3d had matches with West African populations, indicating that these lineages probably entered Europe through Iberia. One lineage L2a1a, appeared to be much older, indicating that it may have entered Europe in prehistoric times. This clade was possibly related to L2a1 clades identified in ten individuals of Ashkenazi heritage from France, Germany, Poland, Romania and Russia. L2a lineages are widespread throughout Africa, as a result the origins of this lineage are uncertain.
Haplogroup M1 is also found in Europe at low frequencies. In a study by Gonzalez et al. 2007, haplogroup M1 had a frequency of 0.3%. The highest frequencies were found in Sicily
Sicily
Sicily is a region of Italy, and is the largest island in the Mediterranean Sea. Along with the surrounding minor islands, it constitutes an autonomous region of Italy, the Regione Autonoma Siciliana Sicily has a rich and unique culture, especially with regard to the arts, music, literature,...
where 3.8% of the population were members of haplogroup M1. The origins of haplogroup M1 have yet to be conclusively established. One clade of haplgroup M1, M1a is widely accepted to be of East African origin. About 40% of all clades of M1 found in Europe are M1a and consequently of recent East African origin.
Haplogroup L lineages frequencies (> 1%)
| Country | Region | Number tested | Study | % |
| Italy | Latium Latium Lazio is one of the 20 administrative regions of Italy, situated in the central peninsular section of the country. With about 5.7 million residents and a GDP of more than 170 billion euros, Lazio is the third most populated and the second richest region of Italy... |
138 | Achilli et al. (2007) | 2.90% |
| Italy | Tuscany Tuscany Tuscany is a region in Italy. It has an area of about 23,000 square kilometres and a population of about 3.75 million inhabitants. The regional capital is Florence .... |
114 | Achilli et al. (2007) | 2.63% |
| Italy | Basilicata Basilicata Basilicata , also known as Lucania, is a region in the south of Italy, bordering on Campania to the west, Apulia to the north and east, and Calabria to the south, having one short southwestern coastline on the Tyrrhenian Sea between Campania in the northwest and Calabria in the southwest, and a... |
92 | Ottoni et al. (2009) | 2.20% |
| Italy | Sicily Sicily Sicily is a region of Italy, and is the largest island in the Mediterranean Sea. Along with the surrounding minor islands, it constitutes an autonomous region of Italy, the Regione Autonoma Siciliana Sicily has a rich and unique culture, especially with regard to the arts, music, literature,... |
154 | Ottoni et al. (2009) | 2.00% |
| Iberia | South Iberia | 310 | Casas et al. (2006) | 7.40% |
| Spain | All regions | 312 | Alvarez et al. (2007) | 2.90% |
| Spain | 496 | Pereira et al. (2005) | 1.61% | |
| Spain | Galicia | 92 | Pereira et al. (2005) | 3.30% |
| Spain | North East | 118 | Pereira et al. (2005) | 2.54% |
| Spain | Zamora | 214 | Alvarez et al. (2010) | 4.70% |
| Spain | Sayago Sayago Sayago is a comarca in the province of Zamora, central Spain.- Geography :The comarca is located at the southwest of the Zamora province. The main geographical characteristic is the isolation caused by the Duero and Tormes rivers canyons... |
33 | Alvarez et al. (2010) | 18.18% |
| Spain | Cordoba Córdoba, Spain -History:The first trace of human presence in the area are remains of a Neanderthal Man, dating to c. 32,000 BC. In the 8th century BC, during the ancient Tartessos period, a pre-urban settlement existed. The population gradually learned copper and silver metallurgy... |
108 | Casas et al. (2006) | 8.30% |
| Spain | Catalonia Catalonia Catalonia is an autonomous community in northeastern Spain, with the official status of a "nationality" of Spain. Catalonia comprises four provinces: Barcelona, Girona, Lleida, and Tarragona. Its capital and largest city is Barcelona. Catalonia covers an area of 32,114 km² and has an... |
101 | Alvarez-Iglesias et al. (2009) | 2.97% |
| Spain | Balearic Islands Balearic Islands The Balearic Islands are an archipelago of Spain in the western Mediterranean Sea, near the eastern coast of the Iberian Peninsula.The four largest islands are: Majorca, Minorca, Ibiza and Formentera. The archipelago forms an autonomous community and a province of Spain with Palma as the capital... |
231 | Picornell et al. (2005) | 2.20% |
| Spain | Canary Islands Canary Islands The Canary Islands , also known as the Canaries , is a Spanish archipelago located just off the northwest coast of mainland Africa, 100 km west of the border between Morocco and the Western Sahara. The Canaries are a Spanish autonomous community and an outermost region of the European Union... |
300 | Brehm et al. (2003) | 6.60% |
| Portugal | 594 | Achilli et al. (2007) | 6.90% | |
| Portugal | North | 188 | Achilli et al. (2007) | 3.19% |
| Portugal | Center | 203 | Achilli et al. (2007) | 6.40% |
| Portugal | South | 203 | Achilli et al. (2007) | 10.84% |
| Portugal | 549 | Pereira et al. (2005) | 5.83% | |
| Portugal | North | 187 | Pereira et al. (2005) | 3.21% |
| Portugal | Center | 239 | Pereira et al. (2005) | 5.02% |
| Portugal | South | 123 | Pereira et al. (2005) | 11.38% |
| Portugal | North | 100 | Pereira et al. (2010) | 5.00% |
| Portugal | Center | 82 | Pereira et al. (2010) | 9.70% |
| Portugal | South | 59 | Pereira et al. (2010) | 6.80% |
| Portugal | Alcacer do Sal | 50 | Pereira et al. (2010) | 22% |
| Portugal | Coruche | 160 | Pereira et al. (2010) | 8.7% |
| Portugal | Pias | 75 | Pereira et al. (2010) | 3.9% |
| Portugal | Madeira Madeira Madeira is a Portuguese archipelago that lies between and , just under 400 km north of Tenerife, Canary Islands, in the north Atlantic Ocean and an outermost region of the European Union... |
155 | Brehm et al. (2003) | 12.90% |
| Portugal | Azores Azores The Archipelago of the Azores is composed of nine volcanic islands situated in the middle of the North Atlantic Ocean, and is located about west from Lisbon and about east from the east coast of North America. The islands, and their economic exclusion zone, form the Autonomous Region of the... |
179 | Brehm et al. (2003) | 3.40% |
| Cyprus | Cyprus Cyprus Cyprus , officially the Republic of Cyprus , is a Eurasian island country, member of the European Union, in the Eastern Mediterranean, east of Greece, south of Turkey, west of Syria and north of Egypt. It is the third largest island in the Mediterranean Sea.The earliest known human activity on the... |
91 | Irwin et al. (2008) | 3.30% |
Autosomal
- A 2011 study by Moorjani et al. found that almost all Southern Europeans have inherited 1%–3% Sub-Saharan ancestry (3.2% in Portugal, 2.9% in Sardinia, 2.7% in Southern Italy, 2.4% in Spain and 1.1% in Northern Italy) with an average mixture date of around 55 generations ago, "consistent with North African gene flow at the end of the Roman Empire and subsequent Arab migrations".
- Measures of genetic distanceGenetic distanceGenetic distance refers to the genetic divergence between species or between populations within a species. It is measured by a variety of parameters. Smaller genetic distances indicate a close genetic relationship whereas large genetic distances indicate a more distant genetic relationship...
between Europe and Sub-Saharan are generally smaller than Genetic distances between Africa and other continental populations. Cavalli-Sforza states that the relatively short genetic distance is likely due to prehistoric admixture. - A 2009 study by Auton et al. found a North-South Cline of Hapmap Yoruba haplotypes (YRI) in Europe. The study determined that South and Southwest subpopulations had the highest proportion of YRI. This distribution is indicative of recurrent gene flow into Europe from the Southwest and the Middle East. The authors suggest that the haplotype sharing between Europe and the YRI are suggestive of gene flow from Africa, albeit from West Africa and not necessarily North Africa.
- A 2007 study conducted at Penn State University found low levels of African admixture(2.8-10%) that were distributed along a North South cline. The authors suggest that the distribution of this African admixture mirrors the distribution of haplogroup E3b-M35(E1b1b).
- A principal component analysis of data from Human Genome Diversity Project by Reich et al. detected a West-to-East gradient of Bantu related ancestry across Eurasia. The authors suggest that after the Out of Africa migration, there was most likely a later Bantu-related gene flow into Europe.
Ancestry informative markers (AIMs)
A 2009 autosomal study by Moorjani et al. that used between 500K and 1.5 Million SNPs estimated that the proportion of sub-Saharan African ancestry is 2.4% in SpainSpain
Spain , officially the Kingdom of Spain languages]] under the European Charter for Regional or Minority Languages. In each of these, Spain's official name is as follows:;;;;;;), is a country and member state of the European Union located in southwestern Europe on the Iberian Peninsula...
, 1.9 % in Greece
Greece
Greece , officially the Hellenic Republic , and historically Hellas or the Republic of Greece in English, is a country in southeastern Europe....
and 1.5% in Tuscany
Tuscany
Tuscany is a region in Italy. It has an area of about 23,000 square kilometres and a population of about 3.75 million inhabitants. The regional capital is Florence ....
. According to the authors, this is consistent in the case of Spain, with the historically known movement of individuals of North African ancestry into Iberia, although it is possible that this estimate also reflects a wider range of mixture times. Another study by the same author in 2011 that analyzed genome-wide polymorphism data from about 40 West Eurasian groups showed that "almost all Southern Europeans have inherited 1%–3% African ancestry with an average mixture date of around 55 generations ago, consistent with North African gene flow at the end of the Roman Empire and subsequent Arab migrations". According to the authors, application of f4 Ancestry Estimation, a method which produces accurate estimates of ancestry proportions, even in the absence of data from the true ancestral populations, suggests that the "highest proportion of African ancestry in Europe is in Iberia (Portugal 3.2±0.3% and Spain 2.4±0.3%), consistent with inferences based on mitochondrial DNA and Y chromosomes and the observation by Auton et al. that within Europe, the Southwestern Europeans have the highest haplotype-sharing with Africans". The authors found the following West African admixture proportions in Europe using f4 Ancestry Estimation :
| Population | West African (>1%°) |
| Portugal | 3.2% |
| Sardinian | 0% |
| Southern Italy | 2.7% |
| Spain | 2.4% |
| Northern Italy | 1.1% |
HLA
One of the most convincing evidences of gene flow from Africa is the A30-B18-DR3 haplotypeA30-Cw5-B18-DR3-DQ2 (HLA Haplotype)
HLA A30-Cw5-B18-DR3-DQ2 is a multigene haplotype that extends across a majority of the major histocompatibility complex on human chromosome 6. A multigene haplotype is a set of inherited alleles covering several genes, or gene-alleles. Long haplotypes, like A30::DQ2, are generally the result of...
, this or component haplotypes reaches a peak frequency in Sardinia with components of ~20%. Three independent studies conclude this haplotype is paleo North African in origin. Several HLA haplotypes and alleles that appear to be of recent Africa origin are found in Europe with frequencies declining from SW to north east similar to A30-B18-DR3.
A number of other alleles including, Cw*0501, Cw*0701 and Cw*1601 appear restricted to European and African populations. This pattern has been described as being suggestive of a close historical relationship between Europeans and Africans.
GM immunoglobulin allotypes
Further studies have shown the presence of haplotype GM*1,17 23' 5* in southern Europe. This haplotype is considered a genetic marker of subSaharan Africa, where it shows frequencies of about 80%. Whereas in non-Mediterranean European populations that value is about 0.3%, in Spain the average figure for this African haplotype is nearly eight times greater(though still low levels) at 2.4% and it shows a peak at 4.5% in Galicia. Values of around 4% have also been found in HuelvaHuelva
Huelva is a city in southwestern Spain, the capital of the province of Huelva in the autonomous region of Andalusia. It is located along the Gulf of Cadiz coast, at the confluence of the Odiel and Tinto rivers. According to the 2010 census, the city has a population of 149,410 inhabitants. The...
, in the Aran valley in the Pyrenees
Pyrenees
The Pyrenees is a range of mountains in southwest Europe that forms a natural border between France and Spain...
and the large islands of Sicily
Sicily
Sicily is a region of Italy, and is the largest island in the Mediterranean Sea. Along with the surrounding minor islands, it constitutes an autonomous region of Italy, the Regione Autonoma Siciliana Sicily has a rich and unique culture, especially with regard to the arts, music, literature,...
(ranging from 1.56% at Valledolmo to 5.5% at Alia), Corsica
Corsica
Corsica is an island in the Mediterranean Sea. It is located west of Italy, southeast of the French mainland, and north of the island of Sardinia....
and Sardinia
Sardinia
Sardinia is the second-largest island in the Mediterranean Sea . It is an autonomous region of Italy, and the nearest land masses are the French island of Corsica, the Italian Peninsula, Sicily, Tunisia and the Spanish Balearic Islands.The name Sardinia is from the pre-Roman noun *sard[],...
. According to Calderon et al. 2007, although some researchers have associated African traces in Iberia to Islamic invasions, the presence of GM*1,17 23' 5* haplotype in Iberia may in fact be due to more ancient processes as well as more recent ones through the introduction of genes from black slaves from Africa.
Sickle cell trait
Sickle cell genes of African origin have been detected in Europe, mostly in the Mediterranean region. The sickle cell traitSickle cell trait
Sickle cell trait describes a condition in which a person has one abnormal allele of the hemoglobin beta gene , but does not display the severe symptoms of sickle cell disease that occur in a person who has two copies of that allele...
is associated with resistance to malaria
Malaria
Malaria is a mosquito-borne infectious disease of humans and other animals caused by eukaryotic protists of the genus Plasmodium. The disease results from the multiplication of Plasmodium parasites within red blood cells, causing symptoms that typically include fever and headache, in severe cases...
. Individuals with one copy of the sickle cell gene, heterozygotes, have higher resistance to malaria than individuals with no sickle cell genes. In regions affected by malaria, the fertility of sickle cell heterozygotes will be higher than average. Individuals with two copies of the sickle cell gene, homozygotes, will be affected by sickle cell disease and historically have had lower than average fertility. The sickle cell trait is thus an example of heterozygote advantage
Heterozygote advantage
A heterozygote advantage describes the case in which the heterozygote genotype has a higher relative fitness than either the homozygote dominant or homozygote recessive genotype. The specific case of heterozygote advantage is due to a single locus known as overdominance...
which is subject to balancing selection
Balancing selection
Balancing selection refers to a number of selective processes by which multiple alleles are actively maintained in the gene pool of a population at frequencies above that of gene mutation. This usually happens when the heterozygotes for the alleles under consideration have a higher adaptive value...
. When the sickle cell trait is introduced into a region affected by malaria, balancing selection will on one hand act to increase the frequency of the trait to counter malaria. On the other hand if the frequency of the trait in the population becomes high enough so that homozygotes with sickle cell disease become common, balancing selection will act to limit the spread of the trait. Therefore in regions affected by malaria, the sickle cell trait is maintained at intermediate frequencies relative to the incidence of malaria.
In Africa, malaria is believed to be one of the most important factors that contributed to restricting population growth in prehistoric times. Sickle cell mutations are believed to have occurred independently at least five times. Four variants are of African origin and one of Indian/Arabian origin. The African variants are referred to as Cameroon, Senegal, Benin and Bantu. The emergence of the sickle cell trait would have contributed to population expansion, with the emergence of farming into tropical regions where malaria was endemic.
Archeological and historical evidence suggest that the malaria had been endemic in the
Mediterranean regions of Europe in historical times. In Eastern Mediterranean regions, such as Italy, Greece, Albania and Turkey the Benin haplotype is the most frequent sickle cell variant. The Benin haplotype is also the most frequent variant in the Middle East and has been observed in Syrians, Palestinians, Israeli Arabs, Israeli Jews and Western Saudi Arabians. This suggests that the Benin haplotype may have expanded from West Africa into North Africa and then into the Middle East and Europe. The spread of the Benin haplotype to the Mediterranean region has been associated with various events including Late Stone Age expansions from West Africa into North Africa, the trans-Saharan trade
Trans-Saharan trade
Trans-Saharan trade requires travel across the Sahara to reach sub-Saharan Africa. While existing from prehistoric times, the peak of trade extended from the 8th century until the late 16th century.- Increasing desertification and economic incentive :...
and the Arab Slave Trade
Arab slave trade
The Arab slave trade was the practice of slavery in the Arab World, mainly Western Asia, North Africa, East Africa and certain parts of Europe during their period of domination by Arab leaders. The trade was focused on the slave markets of the Middle East and North Africa...
. The occurrence of sickle cell trait is particularly high in Sicily
Sicily
Sicily is a region of Italy, and is the largest island in the Mediterranean Sea. Along with the surrounding minor islands, it constitutes an autonomous region of Italy, the Regione Autonoma Siciliana Sicily has a rich and unique culture, especially with regard to the arts, music, literature,...
where frequencies of 13% have been reported. In New York City, Sicilian Americans are second to African Americans in occurrence of Sickle cell disease. The high frequencies of the trait have been associated with the Arab invasion of Sicily in the 7th Century during which Sudanese soldiers were recruited by the Caliphate. Portugal is the only region in Europe where the Senegal and Bantu haplotypes are frequent. These may be associated with Portuguese naval exploits, including the Atlantic Slave Trade
Atlantic slave trade
The Atlantic slave trade, also known as the trans-atlantic slave trade, refers to the trade in slaves that took place across the Atlantic ocean from the sixteenth through to the nineteenth centuries...
and the colonization of various African countries.
In Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
, the highest prevalence of the disease has been observed in France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
as a result of population growth in African-Caribbean regions of overseas France
Overseas departments and territories of France
The French Overseas Departments and Territories consist broadly of French-administered territories outside of the European continent. These territories have varying legal status and different levels of autonomy, although all have representation in the Parliament of France , and consequently the...
, and now immigration essentially from North
North Africa
North Africa or Northern Africa is the northernmost region of the African continent, linked by the Sahara to Sub-Saharan Africa. Geopolitically, the United Nations definition of Northern Africa includes eight countries or territories; Algeria, Egypt, Libya, Morocco, South Sudan, Sudan, Tunisia, and...
and sub-Saharan Africa
Sub-Saharan Africa
Sub-Saharan Africa as a geographical term refers to the area of the African continent which lies south of the Sahara. A political definition of Sub-Saharan Africa, instead, covers all African countries which are fully or partially located south of the Sahara...
to mainland France. SCD has become the most common genetic disease in this country. In 2007, 28.45% of all newborns in mainland France in 2007 had at least one parent originated from a region defined "at risk" (mainly Africa and Overseas departments and territories of France) and were screened for SCD. The Paris metropolitan district (Île-de-France
Île-de-France (région)
Île-de-France is the wealthiest and most populated of the twenty-two administrative regions of France, composed mostly of the Paris metropolitan area....
) is the region that accounts for the largest number of at-risk. Indeed, nearly 56% of all newborns in this area in 2007 had at least one parent originated from a region defined as "at-risk" and were screened for SCD. The second largest number of at-risk is in Provence-Alpes-Côte d'Azur
Provence-Alpes-Côte d'Azur
Provence-Alpes-Côte d'Azur or PACA is one of the 27 regions of France.It is made up of:* the former French province of Provence* the former papal territory of Avignon, known as Comtat Venaissin...
at nearly 42% and the lowest number is in Brittany
Brittany
Brittany is a cultural and administrative region in the north-west of France. Previously a kingdom and then a duchy, Brittany was united to the Kingdom of France in 1532 as a province. Brittany has also been referred to as Less, Lesser or Little Britain...
at 4.40%.
Paleoanthropology
The migration of farmers from the Middle East into Europe is believed to have significantly influenced the genetic profile of contemporary Europeans. Some recent studies have focused on corroborating current genetic data with the archeological evidence from Europe, the Middle East and Africa. The Natufian cultureNatufian culture
The Natufian culture was a Mesolithic culture that existed from 12,500 to 9,500 BC in the Levant, a region in the Eastern Mediterranean. It was unusual in that it was sedentary, or semi-sedentary, before the introduction of agriculture...
which existed about 12,000 years ago in Palestine, has been the subject of various archeological investigations as the Natufian culture is generally believed to be the source of the European and North African Neolithic.
According to a hypothesis stated by , Natufian culture
Natufian culture
The Natufian culture was a Mesolithic culture that existed from 12,500 to 9,500 BC in the Levant, a region in the Eastern Mediterranean. It was unusual in that it was sedentary, or semi-sedentary, before the introduction of agriculture...
emerged from the mixing of two stone age cultures: (1) the Kebaran
Kebaran
The Kebaran or Kebarian culture was an archaeological culture in the eastern Mediterranean area , named after its type site, Kebara Cave south of Haifa...
, a culture indigenous to the Levant and (2) the Mushabian
Mushabian culture
The Mushabian culture is suggested to have originated along the Nile Valley prior to migrating to the Levant, due to similar industries demonstrated among archaeological sites in both regions but with the Nile valley sites predating those found in the Sinai regions of the Levant.Accordingly...
, a culture introduced into the Levant from North Africa. This Mushabian culture is suggested to have originated in Africa as archeological sites with Mushabian industries in the Nile Valley predate those in the Levant. The Mushabians would have then moved into the Sinai from the Nile Delta bringing with them their technologies. states: "the population overflow from Northeast Africa played a definite role in the establishment of the Natufian adaptation, which in turn led to the emergence of agriculture as a new subsistence system".
A study by analysed human remains from the Natufian culture.
According to the study, there is evidence of Sub-Saharan influences in the Natufian samples. They argue that these influences would have been diluted by the interbreeding of the Neolithic farmers from the Near East with the indigenous foragers in Europe. associate the Sub-Saharan influences detected in the Natufian samples with the migration of E1b1b lineages from East Africa to the Levant and then into Europe.
See also
- ArchaeogeneticsArchaeogeneticsArchaeogenetics, a term coined by Colin Renfrew, refers to the application of the techniques of molecular population genetics to the study of the human past. This can involve:*the analysis of DNA recovered from archaeological remains, i.e...
- Archaeogenetics of the Near EastArchaeogenetics of the Near EastThe archaeogenetics of the Near East involves the study of aDNA or ancient DNA, identifying haplogroups and haplotypes of ancient skeletal remains from both YDNA and mtDNA for populations of the Ancient Near East The archaeogenetics of the Near East involves the study of aDNA or ancient DNA,...
- CaucasoidCaucasian raceThe term Caucasian race has been used to denote the general physical type of some or all of the populations of Europe, North Africa, the Horn of Africa, Western Asia , Central Asia and South Asia...
- European ethnic groups
- Human genetic variationHuman genetic variationHuman genetic variation refers to genetic differences both within and among populations. There may be multiple variants of any given gene in the human population , leading to polymorphism. Many genes are not polymorphic, meaning that only a single allele is present in the population: that allele is...
- Population geneticsPopulation geneticsPopulation genetics is the study of allele frequency distribution and change under the influence of the four main evolutionary processes: natural selection, genetic drift, mutation and gene flow. It also takes into account the factors of recombination, population subdivision and population...
- White peopleWhite peopleWhite people is a term which usually refers to human beings characterized, at least in part, by the light pigmentation of their skin...
- Genetic history of EuropeGenetic history of EuropeThe genetic history of Europe can be inferred from the patterns of genetic diversity across continents and time. The primary data to develop historical scenarios coming from sequences of mitochondrial, Y-chromosome and autosomal DNA from modern populations and if available from ancient DNA...
- Afro-AbkhaziansAfro-AbkhaziansAbkhazians of African descent are a small group in Abkhazia of African descent who used to live mainly in the Abkhazian settlement Adzyubzha at the mouth of the Kodori River and the surrounding villages of Abkhazia on the eastern coast of the Black Sea.-Hypotheses:The ethnic origin of the...