Identical ancestors point
Encyclopedia
In genetic genealogy
, the identical ancestors point (IAP) is that point in a given population's past where each individual then alive turned out to be either the ancestor of every individual alive now, or to have no living descendants at all. This point lies further in the past than the population's most recent common ancestor
(MRCA).
The MRCA had many contemporary companions of both sexes. Many of these contemporaries left direct descendants, but not all of them left an unbroken link of descendants all the way down to today's population. That is, some contemporaries are ancestors of no one in current population. The rest of contemporaries of MRCA may claim ancestry over a subset of current population, but not the entirety of current population.
Because ancestors of the MRCA are by definition also common ancestors, we can continue to find (less recent) common ancestors by pushing further back in time to more and more ancient common ancestors of all people alive today. Eventually we will reach a point in the past where all humans can be divided into two groups: those who left no descendants today and those who are common ancestors of all living humans today. This point in time is termed the identical ancestors point. Even though each living person receives genes in dramatically different proportions from these ancestors from the identical ancestors point, all living people share exactly the same set of ancestors from this point back, all the way to the very first single-celled organism.
The identical ancestors point for Homo sapiens has been estimated to between 15,000
and 5,000
years ago, with an estimate of the human MRCA living about 2,000 to 5,000 years ago, that is, estimating the IAP to be about three times as distant as the MRCA. Note that both the matrilineal and the patrilineal human MRCAs are far more remote still, dating to some 150,000 and 90,000 years ago, respectively.
It is incorrect to assume that the MRCA and his/her ancestors passed all their genes down to every person alive today. Because of sexual reproduction
, at every generation, an ancestor only passes half of his or her genes to the next generation. The percentage of genes inherited from the MRCA becomes smaller and smaller at every successive generation, as genes inherited from contemporaries of MRCA are interchanged via sexual reproduction.
As the human genome
consists of roughly 232 base pairs, the genetic contribution of a single ancestor may be flushed out of an individual's genome completely after 32 generations, or roughly 1,000 years.
Genetic genealogy
Genetic genealogy is the application of genetics to traditional genealogy. Genetic genealogy involves the use of genealogical DNA testing to determine the level of genetic relationship between individuals.-History:...
, the identical ancestors point (IAP) is that point in a given population's past where each individual then alive turned out to be either the ancestor of every individual alive now, or to have no living descendants at all. This point lies further in the past than the population's most recent common ancestor
Most recent common ancestor
In genetics, the most recent common ancestor of any set of organisms is the most recent individual from which all organisms in the group are directly descended...
(MRCA).
The MRCA had many contemporary companions of both sexes. Many of these contemporaries left direct descendants, but not all of them left an unbroken link of descendants all the way down to today's population. That is, some contemporaries are ancestors of no one in current population. The rest of contemporaries of MRCA may claim ancestry over a subset of current population, but not the entirety of current population.
Because ancestors of the MRCA are by definition also common ancestors, we can continue to find (less recent) common ancestors by pushing further back in time to more and more ancient common ancestors of all people alive today. Eventually we will reach a point in the past where all humans can be divided into two groups: those who left no descendants today and those who are common ancestors of all living humans today. This point in time is termed the identical ancestors point. Even though each living person receives genes in dramatically different proportions from these ancestors from the identical ancestors point, all living people share exactly the same set of ancestors from this point back, all the way to the very first single-celled organism.
The identical ancestors point for Homo sapiens has been estimated to between 15,000
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....
and 5,000
4th millennium BC
The 4th millennium BC saw major changes in human culture. It marked the beginning of the Bronze Age and of writing.The city states of Sumer and the kingdom of Egypt were established and grew to prominence. Agriculture spread widely across Eurasia...
years ago, with an estimate of the human MRCA living about 2,000 to 5,000 years ago, that is, estimating the IAP to be about three times as distant as the MRCA. Note that both the matrilineal and the patrilineal human MRCAs are far more remote still, dating to some 150,000 and 90,000 years ago, respectively.
It is incorrect to assume that the MRCA and his/her ancestors passed all their genes down to every person alive today. Because of sexual reproduction
Sexual reproduction
Sexual reproduction is the creation of a new organism by combining the genetic material of two organisms. There are two main processes during sexual reproduction; they are: meiosis, involving the halving of the number of chromosomes; and fertilization, involving the fusion of two gametes and the...
, at every generation, an ancestor only passes half of his or her genes to the next generation. The percentage of genes inherited from the MRCA becomes smaller and smaller at every successive generation, as genes inherited from contemporaries of MRCA are interchanged via sexual reproduction.
As the human genome
Human genome
The human genome is the genome of Homo sapiens, which is stored on 23 chromosome pairs plus the small mitochondrial DNA. 22 of the 23 chromosomes are autosomal chromosome pairs, while the remaining pair is sex-determining...
consists of roughly 232 base pairs, the genetic contribution of a single ancestor may be flushed out of an individual's genome completely after 32 generations, or roughly 1,000 years.
See also
- 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...
- Genetic genealogyGenetic genealogyGenetic genealogy is the application of genetics to traditional genealogy. Genetic genealogy involves the use of genealogical DNA testing to determine the level of genetic relationship between individuals.-History:...
- Genealogical DNA testGenealogical DNA testA genealogical DNA test examines the nucleotides at specific locations on a person's DNA for genetic genealogy purposes. The test results are not meant to have any informative medical value and do not determine specific genetic diseases or disorders ; they are intended only to give genealogical...
- GenealogyGenealogyGenealogy is the study of families and the tracing of their lineages and history. Genealogists use oral traditions, historical records, genetic analysis, and other records to obtain information about a family and to demonstrate kinship and pedigrees of its members...
- Last universal ancestorLast universal ancestorThe last universal ancestor , also called the last universal common ancestor , or the cenancestor, is the most recent organism from which all organisms now living on Earth descend. Thus it is the most recent common ancestor of all current life on Earth...
- Most recent common ancestorMost recent common ancestorIn genetics, the most recent common ancestor of any set of organisms is the most recent individual from which all organisms in the group are directly descended...
- Pedigree collapsePedigree collapseIn genealogy, pedigree collapse describes how reproduction between two individuals who knowingly or unknowingly share an ancestor causes the number of distinct ancestors in the family tree of their offspring to be smaller than it could otherwise be. Robert C...
- Phylogenetic treePhylogenetic treeA phylogenetic tree or evolutionary tree is a branching diagram or "tree" showing the inferred evolutionary relationships among various biological species or other entities based upon similarities and differences in their physical and/or genetic characteristics...
- Recent African origin
External links
- Identical ancestors point - explaining the relationship of "most recent common ancestor" and "identical ancestors point"