Albert Perry was an ordinary African American man whose DNA turned out to carry the most distant branch of the human male family tree ever found.1PubMed Central. An African American paternal lineage adds an extremely ancient root to the human Y chromosome phylogenetic tree His lineage, named A00, split from all other known male lines before any of them split from each other.2PubMed Central. An African American Paternal Lineage Adds an Extremely Ancient Root to the Human Y Chromosome Phylogenetic Tree How far back that split happened is still argued over, and the first headline-making age has been challenged by other researchers.3PubMed Central. The ‘extremely ancient’ chromosome that isn’t: a forensic bioinformatic investigation of Albert Perry’s X-degenerate portion of the Y chromosome
What Scientists Found in Albert Perry’s DNA
The Y chromosome is passed almost unchanged from father to son, so it traces a single unbroken male line. Small spelling changes in its DNA pile up over the generations and sort men into branches called haplogroups. Researchers compare many men’s sequences side by side, and a swap shared by a group of men marks them as relatives on one branch.
Perry’s Y chromosome lacked every change that marks the deepest known branches of the tree. It kept the original version at all of them.4PubMed Central. An African American paternal lineage adds an extremely ancient root to the human Y chromosome phylogenetic tree That meant it could not belong to any existing branch and sat outside them all. Researchers then read about 240,000 letters of his Y chromosome to find changes unique to his line.5PubMed Central. An African American paternal lineage adds an extremely ancient root to the human Y chromosome phylogenetic tree They named this new branch A00.6PubMed Central. An African American Paternal Lineage Adds an Extremely Ancient Root to the Human Y Chromosome Phylogenetic Tree
Carrying the original spelling at every marker is what places him on the oldest branch. A man who still has the original version everywhere must have split off before any of the changes appeared. That shows the order of branching, not that Perry himself is ancient: every living man is equally far in time from the shared root. Nor is he descended from a different species. His lineage is fully human, only its branch is distinct, and the rest of his DNA is as ordinary as anyone’s. One well-sequenced man was enough to redraw the tree, because the root has to connect all lines, including his.
A00 was spotted in a large database of African American customers of a genetic testing company.7PubMed Central. An African American paternal lineage adds an extremely ancient root to the human Y chromosome phylogenetic tree It had not turned up in the traditional hunter-gatherer groups of sub-Saharan Africa that geneticists had long studied.8PubMed Central. An African American paternal lineage adds an extremely ancient root to the human Y chromosome phylogenetic tree
Where the A00 Lineage Lives Today
A00 is common enough to notice only in Cameroon.9PubMed Central. Ancient West African foragers in the context of African population history There it is concentrated among the Mbo and Bangwa peoples in the west of the country.10PubMed Central. Ancient West African foragers in the context of African population history Perry’s male-line ancestors very likely came from that region, probably through the Atlantic slave trade. Many enslaved Africans were taken from West-Central Africa, which is why a database of African Americans can reveal lineages that fieldwork in Africa missed.
A00 has also been found in the DNA of ancient West African foragers.11PubMed Central. Ancient West African foragers in the context of African population history Others buried in the same study region carried branch B, a lineage now common in Central African hunter-gatherers.12PubMed Central. Ancient West African foragers in the context of African population history Finding A00 at noticeable levels only in Cameroon shows where it survives today, not necessarily where it began, which is why the ancient West African finds matter as supporting evidence.
A lineage needs only one unbroken chain of sons to survive. Small, stable communities can keep a rare branch for many generations, while a branch vanishes the moment a man has no sons.
Other deep branches cluster nearby. Another very deep branch, A1b, was first found in only three men from Cameroon.13PubMed Central. Molecular Dissection of the Basal Clades in the Human Y Chromosome Phylogenetic Tree
How Old Is A00, Really
The discoverers estimated that the common male ancestor of A00 and all other lines lived about 338,000 years ago.14PubMed Central. An African American Paternal Lineage Adds an Extremely Ancient Root to the Human Y Chromosome Phylogenetic Tree Their range of uncertainty ran from about 237,000 to 581,000 years ago.15PubMed Central. The ‘extremely ancient’ chromosome that isn’t: a forensic bioinformatic investigation of Albert Perry’s X-degenerate portion of the Y chromosome So even the original figure was a broad window, not a precise date.
Other researchers published a critique titled “The extremely ancient chromosome that isn’t.”16PubMed Central. The ‘extremely ancient’ chromosome that isn’t: a forensic bioinformatic investigation of Albert Perry’s X-degenerate portion of the Y chromosome Revisions to the age have since been proposed, and the matter is not settled.17PubMed Central. The Y Chromosome: A Complex Locus for Genetic Analyses of Complex Human Traits In news stories, treat 338,000 as an early, contested figure. Later estimates generally pulled the age closer in time, and the order of the branches is far less disputed than the date.
Scientists date splits by counting changes and dividing by how fast changes appear each generation. It works like a clock: if changes accumulate at a roughly steady pace, more differences between two lines means more time since they split. Generations are then converted to years using an assumed average age of fathers, which adds one more assumption.
The pace of mutation is where the trouble starts. Rates measured within families tend to run slightly faster than rates measured from ancient DNA.18PubMed. Toward a consensus on SNP and STR mutation rates on the human Y-chromosome Experts suggest reporting ages as a range between those two rates.19PubMed. Toward a consensus on SNP and STR mutation rates on the human Y-chromosome A faster assumed rate makes the same changes look younger, and a slower one stretches the age back. Small differences in rate can shift dates by tens of thousands of years.
One widely used family-based rate rested on just 4 observed mutations.20PubMed Central. Sequencing Y Chromosomes Resolves Discrepancy in Time to Common Ancestor of Males versus Females Every age estimate divides by the rate, so an error there carries straight into the final date. Modern DNA sequencing now allows mutation rates to be measured directly.21PubMed. Human Y-chromosome variation in the genome-sequencing era
What A00 Means for Y-Chromosomal Adam
Y-chromosomal Adam is the most recent man from whom all living men descend through an unbroken father-to-son line.22Wikipedia. Y-chromosomal Adam He was not the only man alive in his time.23Wikipedia. Y-chromosomal Adam Other men of his era have living descendants too, just not through sons only.24Wikipedia. Y-chromosomal Adam Those descendants are linked to him through a mix of mothers and fathers, so the other men’s DNA lives on in us, just not on the Y chromosome.
The name is a nickname, not a claim about creation. Mitochondrial Eve is the matching idea for mothers, at a different time, and the two never needed to meet.
The title can shift over history as male lines die out.25Wikipedia. Y-chromosomal Adam It depends on which lines happen to survive. If a branch dies out, the shared ancestor of everyone left can become more recent, because the deepest split is gone. If a deeper branch like A00 is found alive, the shared ancestor must be older, since he now has to connect to that branch as well. Earlier work had already revised the tree’s root using other African branches.26PubMed Central. A Revised Root for the Human Y Chromosomal Phylogenetic Tree: The Origin of Patrilineal Diversity in Africa Full-sequence comparisons place A00 outside all other known branches, so it is the oldest outlier but still part of one connected human tree.27bioRxiv. Examining models of modern human origins through the analysis of 43 fully sequenced human Y chromosomes
How A00 Compares With Neanderthal Y Chromosomes
Researchers compared Neanderthal, A00, and other human Y chromosomes with a chimpanzee’s. The Neanderthal Y came out as the most distantly related.28PubMed Central. The Divergence of Neandertal and Modern Human Y Chromosomes A00 is fully modern human, not a Neanderthal mix. If it were Neanderthal-related, it would sit with the Neanderthal Y in that comparison, but it clusters on the modern human side.
Denisovan Y chromosomes split around 700,000 years ago from the line shared by Neanderthals and modern humans.29PubMed. The evolutionary history of Neanderthal and Denisovan Y chromosomes Neanderthal and modern human Y chromosomes then split around 370,000 years ago.30PubMed. The evolutionary history of Neanderthal and Denisovan Y chromosomes A00’s split falls after the Neanderthal one, inside modern humans. Older A00 dates sat uncomfortably close to the Neanderthal split, which was part of why they were questioned. Late Neanderthals appear to have had their Y chromosomes replaced by lines related to modern humans.31PubMed. The evolutionary history of Neanderthal and Denisovan Y chromosomes
Could Your DNA Test Turn Up Something Like This
Men who take ancestry tests often get a Y haplogroup that names their male-line branch. Women have no Y chromosome and need a father or brother to test their male line.
A typical result is a branch name, often a letter and number code, with a short description of where that branch is common. Most men land on branches shared by millions of others, so a match to a very rare branch like A00 would be exceptional. Branch names can also change as companies update their trees, so the same man may see a different label years later.
Large databases let researchers spot rare branches by scanning many men’s results, which is how A00 surfaced. A database finding still needs full sequencing and careful analysis before scientists treat it as a new branch. Customers usually contribute only if they have agreed to research participation.
Fairness matters here. African DNA research has a history of samples flowing out of Africa with little benefit returned.32PubMed Central. Ethical and legal implications of whole genome and whole exome sequencing in African populations Researchers are urged to share benefits and build trust with African communities.33PubMed Central. Ethical and legal implications of whole genome and whole exome sequencing in African populations Reading a company’s research-consent terms before agreeing is a sensible habit.
If you do get an unusual result, check the branch name against the company’s tree, ask whether you can join research projects, and share it with male relatives who share the line. A deep branch says nothing about health or traits. A Y result also traces only one of thousands of ancestors, since most of your DNA comes from other lines, and it points to a region, not a single village.