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Homo (genus)
Encyclopedia
Homo is the genus
that includes modern humans
and species closely related to them. The genus is estimated to be about 2.3 to 2.4 million years old, evolving from australopithecine
ancestors with the appearance of Homo habilis
.
Specifically, H. habilis is assumed to be the direct descendant of Australopithecus garhi
which lived about 2.5 million years ago. However in May 2010, H. gautengensis was discovered, a species believed to be even older than H. habilis.
The most salient physiological development between the two species is the increase in cranial capacity
, from about 450 cc in A. garhi to 600 cc in H. habilis. Within the Homo genus, cranial capacity again doubled from H. habilis through H. Ergaster or H. Erectus to H. heidelbergensis
by 0.6 million years ago. The cranial capacity of H. heidelbergensis overlaps with the range found in modern humans.
The advent of Homo was thought to coincide with the first evidence of stone tool
s (the Oldowan industry), and thus by definition with the beginning of the Lower Palaeolithic; however, recent evidence from Ethiopia now places the earliest evidence of stone tool usage at before 3.39 million years ago. The emergence of Homo coincides roughly with the onset of Quaternary glaciation
, the beginning of the current ice age
.
All species of the genus except Homo sapiens
(modern humans) are extinct. Homo neanderthalensis, traditionally considered the last surviving relative, died out about 24,000 years ago, while a recent discovery suggests that another species, Homo floresiensis
, discovered in 2003, may have lived as recently as 12,000 years ago. The Denisova hominin
, whose discovery was announced in March 2010, may be yet another past species in the genus. The other extant Homininae
—the chimpanzee
s and gorilla
s—have a limited geographic range. In contrast, the evolution of humans is a history of migrations and admixture. Humans repeatedly left Africa to populate Eurasia and finally the Americas, Oceania, and the rest of the world.
and palaeontology, the common name for all members of the genus Homo is "human".
The word homo is Latin
, in the original sense of "human being", or "man
" (in the gender-neutral sense). The word "human" itself is from Latin humanus, an adjective cognate to homo, both thought to derive from a Proto-Indo-European
word for "earth" reconstructed as .
The binominal name Homo sapiens is due to Carl Linnaeus (1758).
Names for other species were coined beginning in the second half of the 19th century (H. neanderthalensis 1864, H. erectus 1892).
of H. sapiens. Recently, nuclear DNA from a Neanderthal specimen from Vindija Cave
has been sequenced as well, using two different methods that yield similar results regarding Neanderthal and H. sapiens lineages, with both analyses suggesting a date for the split between 460,000 and 700,000 years ago, though a population split of around 370,000 years is inferred. The nuclear DNA results indicate that about 30% of derived alleles in H. sapiens are also in the Neanderthal lineage. This high frequency may suggest some gene flow between ancestral humans and Neanderthal populations.
Homo habilis
, which is considered the first member of the genus Homo, gave rise to Homo ergaster
. Some of the H. ergaster migrated to Asia, where they are named Homo erectus
, and to Europe with Homo georgicus
. H. ergaster in Africa and H. erectus in Eurasia evolved separately for almost two million years and presumably separated into two different species. Homo rhodesiensis
, who were descended from H. ergaster, migrated from Africa to Europe and became Homo heidelbergensis
and later (about 250,000 years ago) Homo sapiens neanderthalensis and the Denisova hominin
in Asia. The first Homo sapiens sapiens, descendants of H. rhodesiensis, appeared in Africa about 250,000 years ago. About 100,000 years ago, some H. sapiens sapiens migrated from Africa to the Levant
and met with resident Neanderthals, with some admixture
. Later, about 70,000 years ago, perhaps after the Toba catastrophe, a small group left the Levant to populate Eurasia
, Australia
and later the Americas. A sub-group among them met the Denisovans and, after further admixture, migrated to populate Melanesia. In this scenario, non-African people living today are mostly of African origin ("Out of Africa model"). However there was also some admixture with Neanderthals and Denisovans, who had evolved locally (the "multiregional hypothesis"). Recent genomic results from the group of Svante Pääbo
also show that 30,000 years ago at least three major subspecies co-existed: Denisovans, Neanderthals and Cro-magnon
s. Today, only H. sapiens sapiens remains, with no other extant species or subspecies.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
that includes modern humans
Anatomically 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....
and species closely related to them. The genus is estimated to be about 2.3 to 2.4 million years old, evolving from australopithecine
Australopithecine
The term australopithecine refers generally to any species in the related genera Australopithecus or Paranthropus. These species occurred in the Plio-Pleistocene era, and were bipedal and dentally similar to humans, but with a brain size not much larger than modern apes, lacking the...
ancestors with the appearance of Homo habilis
Homo habilis
Homo habilis is a species of the genus Homo, which lived from approximately at the beginning of the Pleistocene period. The discovery and description of this species is credited to both Mary and Louis Leakey, who found fossils in Tanzania, East Africa, between 1962 and 1964. Homo habilis Homo...
.
Specifically, H. habilis is assumed to be the direct descendant of Australopithecus garhi
Australopithecus garhi
Australopithecus garhi is a gracile australopithecine species whose fossils were discovered in 1996 by a research team led by Ethiopian paleontologist Berhane Asfaw and Tim White, an American paleontologist. The hominin remains are believed to be a human ancestor species and the final missing link...
which lived about 2.5 million years ago. However in May 2010, H. gautengensis was discovered, a species believed to be even older than H. habilis.
The most salient physiological development between the two species is the increase in cranial capacity
Cranial capacity
Cranial capacity is a measure of the volume of the interior of the cranium of those vertebrates who have both a cranium and a brain. The most commonly used unit of measure is the cubic centimetre or cc...
, from about 450 cc in A. garhi to 600 cc in H. habilis. Within the Homo genus, cranial capacity again doubled from H. habilis through H. Ergaster or H. Erectus to H. heidelbergensis
Homo heidelbergensis
Homo heidelbergensis is an extinct species of the genus Homo which may be the direct ancestor of both Homo neanderthalensis in Europe and Homo sapiens. The best evidence found for these hominins date between 600,000 and 400,000 years ago. H...
by 0.6 million years ago. The cranial capacity of H. heidelbergensis overlaps with the range found in modern humans.
The advent of Homo was thought to coincide with the first evidence of stone tool
Stone tool
A stone tool is, in the most general sense, any tool made either partially or entirely out of stone. Although stone tool-dependent societies and cultures still exist today, most stone tools are associated with prehistoric, particularly Stone Age cultures that have become extinct...
s (the Oldowan industry), and thus by definition with the beginning of the Lower Palaeolithic; however, recent evidence from Ethiopia now places the earliest evidence of stone tool usage at before 3.39 million years ago. The emergence of Homo coincides roughly with the onset of Quaternary glaciation
Quaternary glaciation
Quaternary glaciation, also known as the Pleistocene glaciation, the current ice age or simply the ice age, refers to the period of the last few million years in which permanent ice sheets were established in Antarctica and perhaps Greenland, and fluctuating ice sheets have occurred elsewhere...
, the beginning of the current ice age
Ice age
An ice age or, more precisely, glacial age, is a generic geological period of long-term reduction in the temperature of the Earth's surface and atmosphere, resulting in the presence or expansion of continental ice sheets, polar ice sheets and alpine glaciers...
.
All species of the genus except Homo sapiens
Human
Humans are the only living species in the Homo genus...
(modern humans) are extinct. Homo neanderthalensis, traditionally considered the last surviving relative, died out about 24,000 years ago, while a recent discovery suggests that another species, Homo floresiensis
Homo floresiensis
Homo floresiensis is a possible species, now extinct, in the genus Homo. The remains were discovered in 2003 on the island of Flores in Indonesia. Partial skeletons of nine individuals have been recovered, including one complete cranium...
, discovered in 2003, may have lived as recently as 12,000 years ago. The Denisova hominin
Denisova hominin
Denisova hominins , or Denisovans, are Paleolithic-Era members of the genus Homo that may belong to a previously unknown species. In , scientists announced the discovery of a finger bone fragment of a juvenile female that lived about 41,000 years ago, found in Denisova Cave in Altai Krai, Russia, a...
, whose discovery was announced in March 2010, may be yet another past species in the genus. The other extant Homininae
Homininae
Homininae is a subfamily of Hominidae, which includes humans, gorillas and chimpanzees, and some extinct relatives; it comprises all those hominids, such as Australopithecus, that arose after the split from orangutans . Our family tree, which has 3 main branches leading to chimpanzees, humans and...
—the chimpanzee
Chimpanzee
Chimpanzee, sometimes colloquially chimp, is the common name for the two extant species of ape in the genus Pan. The Congo River forms the boundary between the native habitat of the two species:...
s and gorilla
Gorilla
Gorillas are the largest extant species of primates. They are ground-dwelling, predominantly herbivorous apes that inhabit the forests of central Africa. Gorillas are divided into two species and either four or five subspecies...
s—have a limited geographic range. In contrast, the evolution of humans is a history of migrations and admixture. Humans repeatedly left Africa to populate Eurasia and finally the Americas, Oceania, and the rest of the world.
Naming
In biological sciences, particularly anthropologyAnthropology
Anthropology is the study of humanity. It has origins in the humanities, the natural sciences, and the social sciences. The term "anthropology" is from the Greek anthrōpos , "man", understood to mean mankind or humanity, and -logia , "discourse" or "study", and was first used in 1501 by German...
and palaeontology, the common name for all members of the genus Homo is "human".
The word homo is Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
, in the original sense of "human being", or "man
Man (word)
The term man and words derived from it can designate any or even all of the human race regardless of their sex or age...
" (in the gender-neutral sense). The word "human" itself is from Latin humanus, an adjective cognate to homo, both thought to derive from a Proto-Indo-European
Proto-Indo-European language
The Proto-Indo-European language is the reconstructed common ancestor of the Indo-European languages, spoken by the Proto-Indo-Europeans...
word for "earth" reconstructed as .
The binominal name Homo sapiens is due to Carl Linnaeus (1758).
Names for other species were coined beginning in the second half of the 19th century (H. neanderthalensis 1864, H. erectus 1892).
Species
Species status of Homo rudolfensis, H. ergaster, H. georgicus, H. antecessor, H. cepranensis, H. rhodesiensis and H. floresiensis remains under debate. H. heidelbergensis and H. neanderthalensis are closely related to each other and have been considered to be subspeciesSubspecies
Subspecies in biological classification, is either a taxonomic rank subordinate to species, ora taxonomic unit in that rank . A subspecies cannot be recognized in isolation: a species will either be recognized as having no subspecies at all or two or more, never just one...
of H. sapiens. Recently, nuclear DNA from a Neanderthal specimen from Vindija Cave
Vindija Cave
Vindija is a cave near the city of Varaždin, Croatia. It contains one of the best preserved remains of the Neanderthals in the world, found in 1974. It is estimated that the Neanderthal man lived there about 30,000 years ago....
has been sequenced as well, using two different methods that yield similar results regarding Neanderthal and H. sapiens lineages, with both analyses suggesting a date for the split between 460,000 and 700,000 years ago, though a population split of around 370,000 years is inferred. The nuclear DNA results indicate that about 30% of derived alleles in H. sapiens are also in the Neanderthal lineage. This high frequency may suggest some gene flow between ancestral humans and Neanderthal populations.
Migration and admixture
Homo habilis
Homo habilis is a species of the genus Homo, which lived from approximately at the beginning of the Pleistocene period. The discovery and description of this species is credited to both Mary and Louis Leakey, who found fossils in Tanzania, East Africa, between 1962 and 1964. Homo habilis Homo...
, which is considered the first member of the genus Homo, gave rise to Homo ergaster
Homo ergaster
Homo ergaster is an extinct chronospecies of Homo that lived in eastern and southern Africa during the early Pleistocene, about 2.5–1.7 million years ago.There is still disagreement on the subject of the classification, ancestry, and progeny of H...
. Some of the H. ergaster migrated to Asia, where they are named Homo erectus
Homo erectus
Homo erectus is an extinct species of hominid that lived from the end of the Pliocene epoch to the later Pleistocene, about . The species originated in Africa and spread as far as India, China and Java. There is still disagreement on the subject of the classification, ancestry, and progeny of H...
, and to Europe with Homo georgicus
Homo georgicus
Homo georgicus is a species of Homo that was suggested in 2002 to describe fossil skulls and jaws found in Dmanisi, Georgia in 1999 and 2001, which seem intermediate between Homo habilis and H. erectus. A partial skeleton was discovered in 2001. The fossils are about 1.8 million years old...
. H. ergaster in Africa and H. erectus in Eurasia evolved separately for almost two million years and presumably separated into two different species. Homo rhodesiensis
Homo rhodesiensis
Homo rhodesiensis is a hominin species described from the fossil Kabwe skull. Other morphologically-comparable remains have been found from the same, or earlier, time period in southern Africa , East Africa and North Africa...
, who were descended from H. ergaster, migrated from Africa to Europe and became Homo heidelbergensis
Homo heidelbergensis
Homo heidelbergensis is an extinct species of the genus Homo which may be the direct ancestor of both Homo neanderthalensis in Europe and Homo sapiens. The best evidence found for these hominins date between 600,000 and 400,000 years ago. H...
and later (about 250,000 years ago) Homo sapiens neanderthalensis and the Denisova hominin
Denisova hominin
Denisova hominins , or Denisovans, are Paleolithic-Era members of the genus Homo that may belong to a previously unknown species. In , scientists announced the discovery of a finger bone fragment of a juvenile female that lived about 41,000 years ago, found in Denisova Cave in Altai Krai, Russia, a...
in Asia. The first Homo sapiens sapiens, descendants of H. rhodesiensis, appeared in Africa about 250,000 years ago. About 100,000 years ago, some H. sapiens sapiens migrated from Africa to the Levant
Levant
The Levant or ) is the geographic region and culture zone of the "eastern Mediterranean littoral between Anatolia and Egypt" . The Levant includes most of modern Lebanon, Syria, Jordan, Israel, the Palestinian territories, and sometimes parts of Turkey and Iraq, and corresponds roughly to the...
and met with resident Neanderthals, with some 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...
. Later, about 70,000 years ago, perhaps after the Toba catastrophe, a small group left the Levant to populate 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...
, Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
and later the Americas. A sub-group among them met the Denisovans and, after further admixture, migrated to populate Melanesia. In this scenario, non-African people living today are mostly of African origin ("Out of Africa model"). However there was also some admixture with Neanderthals and Denisovans, who had evolved locally (the "multiregional hypothesis"). Recent genomic results from the group of Svante Pääbo
Svante Pääbo
Svante Pääbo is a Swedish biologist specializing in evolutionary genetics. He was born in 1955 in Stockholm to Sune Bergström, who shared the Nobel Prize in Physiology or Medicine with Bengt I. Samuelsson and John R. Vane in 1982, and his mother, Estonian Karin Pääbo.He earned his PhD from Uppsala...
also show that 30,000 years ago at least three major subspecies co-existed: Denisovans, Neanderthals and 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....
s. Today, only H. sapiens sapiens remains, with no other extant species or subspecies.
See also
- HomininaeHomininaeHomininae is a subfamily of Hominidae, which includes humans, gorillas and chimpanzees, and some extinct relatives; it comprises all those hominids, such as Australopithecus, that arose after the split from orangutans . Our family tree, which has 3 main branches leading to chimpanzees, humans and...
- Human evolutionHuman evolutionHuman evolution refers to the evolutionary history of the genus Homo, including the emergence of Homo sapiens as a distinct species and as a unique category of hominids and mammals...
- List of human evolution fossils
- Timeline of human evolutionTimeline of human evolutionThe timeline of human evolution outlines the major events in the development of human species, and the evolution of humans' ancestors. It includes a brief explanation of some animals, species or genera, which are possible ancestors of Homo sapiens...