A very exciting new paper was released yesterday, confirming the announcement four months ago that the common ancestor to all human male lineages lived much longer ago than what believed so far.
An African American Paternal Lineage Adds an Extremely Ancient Root to the Human Y Chromosome Phylogenetic Tree (Mendez et al.)
Abstract
"We report the discovery of an African American Y chromosome that carries the ancestral state of all SNPs that defined the basal portion of the Y chromosome phylogenetic tree. We sequenced ∼240 kb of this chromosome to identify private, derived mutations on this lineage, which we named A00. We then estimated the time to the most recent common ancestor (TMRCA) for the Y tree as 338 thousand years ago (kya) (95% confidence interval = 237–581 kya). Remarkably, this exceeds current estimates of the mtDNA TMRCA, as well as those of the age of the oldest anatomically modern human fossils. The extremely ancient age combined with the rarity of the A00 lineage, which we also find at very low frequency in central Africa, point to the importance of considering more complex models for the origin of Y chromosome diversity. These models include ancient population structure and the possibility of archaic introgression of Y chromosomes into anatomically modern humans. The A00 lineage was discovered in a large database of consumer samples of African Americans and has not been identified in traditional hunter-gatherer populations from sub-Saharan Africa. This underscores how the stochastic nature of the genealogical process can affect inference from a single locus and warrants caution during the interpretation of the geographic location of divergent branches of the Y chromosome phylogenetic tree for the elucidation of human origins."
The most amazing thing about this re-assessment is that the root of this new African branch (Y-haplogroup A00) is considerably older than the anatomically modern humans, known as Homo Sapiens. It is not until 200,000 years ago that hominids started exhibiting traits that could be characterised as anatomical modernity, while full behavioural modernity only developed from 50,000 years ago (in some parts of the world).
This A00 lineage is at least 237,000 years old, but could be as old as 581,000 years old, based on the mutation rate used by the team of researchers. This bring us back to the Early to Middle Palaeolithic, a period where several (sub)species of hominids co-existed in Africa, Asia and Europe, including Homo erectus (1.8 million to 300,000 ybp), Homo rhodesiensis (300,000 to 125,000 ybp), Homo heidelbergensis (600,000 to 400,000 ybp), Denisovans (?), and of course Neanderthals (600,000 to 25,000 ybp).
I have long supported the Multiregional origin of modern humans as opposed to the Recent African origin of modern humans taught in most schools. The discovery in 2010 that modern Eurasians did indeed have Neanderthal and Denisovan DNA was a first step in confirming the Multiregional origin theory. This paper adds another example of archaic admixture, from Central Africa this time. I believe that the reason why modern human racial groups display such phenotypical diversity is for the greatest part due to these archaic admixtures.
I also believe that the definition of species, as applied to hominids, should be revised accordingly, since members are different species by definition cannot interbreed with one another. Therefore, all archaic humans should be considered as subspecies and not separate species.
Genetic genealogy is a brand new science, which really took off in the last 5 to 10 years. It is likely that even older lineages will be found - if not in living people, at least in relatively recent ancient DNA from the last 10,000 years (like Ötzi).
An African American Paternal Lineage Adds an Extremely Ancient Root to the Human Y Chromosome Phylogenetic Tree (Mendez et al.)
Abstract
"We report the discovery of an African American Y chromosome that carries the ancestral state of all SNPs that defined the basal portion of the Y chromosome phylogenetic tree. We sequenced ∼240 kb of this chromosome to identify private, derived mutations on this lineage, which we named A00. We then estimated the time to the most recent common ancestor (TMRCA) for the Y tree as 338 thousand years ago (kya) (95% confidence interval = 237–581 kya). Remarkably, this exceeds current estimates of the mtDNA TMRCA, as well as those of the age of the oldest anatomically modern human fossils. The extremely ancient age combined with the rarity of the A00 lineage, which we also find at very low frequency in central Africa, point to the importance of considering more complex models for the origin of Y chromosome diversity. These models include ancient population structure and the possibility of archaic introgression of Y chromosomes into anatomically modern humans. The A00 lineage was discovered in a large database of consumer samples of African Americans and has not been identified in traditional hunter-gatherer populations from sub-Saharan Africa. This underscores how the stochastic nature of the genealogical process can affect inference from a single locus and warrants caution during the interpretation of the geographic location of divergent branches of the Y chromosome phylogenetic tree for the elucidation of human origins."
The most amazing thing about this re-assessment is that the root of this new African branch (Y-haplogroup A00) is considerably older than the anatomically modern humans, known as Homo Sapiens. It is not until 200,000 years ago that hominids started exhibiting traits that could be characterised as anatomical modernity, while full behavioural modernity only developed from 50,000 years ago (in some parts of the world).
This A00 lineage is at least 237,000 years old, but could be as old as 581,000 years old, based on the mutation rate used by the team of researchers. This bring us back to the Early to Middle Palaeolithic, a period where several (sub)species of hominids co-existed in Africa, Asia and Europe, including Homo erectus (1.8 million to 300,000 ybp), Homo rhodesiensis (300,000 to 125,000 ybp), Homo heidelbergensis (600,000 to 400,000 ybp), Denisovans (?), and of course Neanderthals (600,000 to 25,000 ybp).
I have long supported the Multiregional origin of modern humans as opposed to the Recent African origin of modern humans taught in most schools. The discovery in 2010 that modern Eurasians did indeed have Neanderthal and Denisovan DNA was a first step in confirming the Multiregional origin theory. This paper adds another example of archaic admixture, from Central Africa this time. I believe that the reason why modern human racial groups display such phenotypical diversity is for the greatest part due to these archaic admixtures.
I also believe that the definition of species, as applied to hominids, should be revised accordingly, since members are different species by definition cannot interbreed with one another. Therefore, all archaic humans should be considered as subspecies and not separate species.
Genetic genealogy is a brand new science, which really took off in the last 5 to 10 years. It is likely that even older lineages will be found - if not in living people, at least in relatively recent ancient DNA from the last 10,000 years (like Ötzi).