Y-chromosomal Adam - Hypothesis


The existence of a Y-chromosomal Adam was determined by applying the theories of molecular evolution to the Y chromosome. Unlike the autosomes, the human Y chromosome does not recombine with the X chromosome but is transferred intact from father to son. Mutations periodically occur within the Y chromosome and these mutations are passed on to males in subsequent generations. These mutations can be used as markers to identify shared patrilineal relationships. Y chromosomes that share a specific mutation are referred to as haplogroups. Y chromosomes within a specific haplogroup share a common patrilineal ancestor who was the first to carry the defining mutation. A family tree of Y chromosomes can be constructed, with the mutations serving as branching points along lineages. Y-chromosomal Adam is positioned at the root of the family tree as the Y chromosomes of all living males are descended from his Y chromosome.

Researchers can reconstruct ancestral Y chromosome DNA sequences by reversing mutated DNA segments to their original condition. The most likely original or ancestral state of a DNA sequence is determined by comparing human DNA sequences with those of a closely related species, usually non-human primates such as chimpanzees and gorillas. By reversing known mutations in a Y-chromosome lineage, a hypothetical ancestral sequence for the MRCA, Y-chromosomal Adam, can be inferred.

Determining Y-chromosomal Adam's DNA sequence, and the time when he lived, involves identifying the human Y-chromosome lineages that are most divergent from each other—the lineages that share the least unique mutations with each other when compared to a non-human primate sequence in a phylogenetic tree. The common ancestor of the most divergent lineages is therefore the common ancestor of all lineages.

The existence of Y-chromosomal Adam was confirmed by a worldwide sample of Y chromosomes that included individuals from all continents. A number of Y-chromosome lineages, or haplogroups, from Africa were found to be the most divergent from each other, and non-African lineages were determined to be subsets of a few lineages found in Africa. This suggested Africa was the most likely home of Y-chromosomal Adam.

Read more about this topic:  Y-chromosomal Adam

Other articles related to "hypothesis":

Descriptive Knowledge - Knowledge in Various Disciplines - Knowledge in Science and Engineering
... picks a question of interest, and based on previous knowledge, develops a hypothesis ... experiment which will allow him to test the hypothesis against the real world ... He then makes predictions about the outcome of the test, based on the hypothesis ...
Eutherian Fetoembryonic Defense System (eu-FEDS) Hypothesis - Hypothesis
... The basic premise of the eu-FEDS hypothesis is that both soluble and cell surface associated glycoproteins, present in the reproductive system and expressed on gametes, suppress any potential immune responses, and ...
Directed Mutagenesis - Recent Studies
... The hypothesis of directed mutagenesis was first proposed in 1988 by John Cairns, of Harvard University who was studying Escherichia coli that lacked the ability to metabolize lactose ... Later support for this hypothesis came from Susan Rosenberg, then at the University of Alberta, who found that an enzyme involved in DNA recombinational repair ... The directed mutagenesis hypothesis was challenged in 2002, when John Roth and colleagues showed that the phenomenon was due to general hypermutability due to selected gene amplification, and was thus a ...
PANDAS - Proposed Mechanism
... The PANDAS diagnosis and the hypothesis that symptoms in this subgroup of patients are caused by infection are controversial ... Researchers are pursuing the hypothesis that the mechanism is similar to that of rheumatic fever, an autoimmune disorder triggered by streptococcal infections, where ... The molecular mimicry hypothesis is a proposed mechanism for PANDAS this hypothesis is that antigens on the cell wall of the streptococcal bacteria are similar in some way to the ...
Hypotheses For The Evolution of Schreckstoff
... The first hypothesis is that the evolution of schreckstoff has been driven by kin selection (Smith 1992) ... Support for this hypothesis would include evidence that individuals live in groups of closely related kin and that the release of chemical alarm signals increases the likelihood that related individuals will ... The second hypothesis, predator attraction, suggests that the release of schreckstoff may attract additional predators which will interfere with the predation event, increasing the likelihood that the ...

Famous quotes containing the word hypothesis:

    The great tragedy of science—the slaying of a beautiful hypothesis by an ugly fact.
    Thomas Henry Huxley (1825–95)

    The hypothesis I wish to advance is that ... the language of morality is in ... grave disorder.... What we possess, if this is true, are the fragments of a conceptual scheme, parts of which now lack those contexts from which their significance derived. We possess indeed simulacra of morality, we continue to use many of the key expressions. But we have—very largely if not entirely—lost our comprehension, both theoretical and practical, of morality.
    Alasdair Chalmers MacIntyre (b. 1929)

    It is an hypothesis that the sun will rise tomorrow: and this means that we do not know whether it will rise.
    Ludwig Wittgenstein (1889–1951)