Human Y chromosome much older than previously thought

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University of Arizona geneticists have discovered the oldest known genetic branch of the human Y chromosome – the hereditary factor determining male sex.
The new divergent lineage, which was found in an individual who submitted his DNA to Family Tree DNA, a company specializing in DNA analysis to trace family roots, branched from the Y chromosome tree before the first appearance of anatomically modern humans in the fossil record. 
The results are published in the American Journal of Human Genetics. 
“Our analysis indicates this lineage diverged from previously known Y chromosomes about 300,000 ago, a time when anatomically modern humans had not yet evolved,” said Michael Hammer, an associate professor in the University of Arizona’s department of ecology and evolutionary biology and a research scientist at the UA’s Arizona Research Labs. “This pushes back the time the last common Y chromosome ancestor lived by almost 70 percent.”
Unlike the other human chromosomes, the majority of the Y chromosome does not exchange genetic material with other chromosomes, which makes it simpler to trace ancestral relationships among contemporary lineages. If two Y chromosomes carry the same mutation, it is because they share a common paternal ancestor at some point in the past. The more mutations that differ between two Y chromosomes the farther back in time the common ancestor lived. 
Originally, a DNA sample obtained from an African American living in South Carolina was submitted to the National Geographic Genographic Project. When none of the genetic markers used to assign lineages to known Y chromosome groupings were found, the DNA sample was sent to Family Tree DNA for sequencing. Fernando Mendez, a postdoctoral researcher in Hammer’s lab, led the effort to analyze the DNA sequence, which included more than 240,000 base pairs of the Y chromosome.
Written By: Phys.org
continue to source article at phys.org

6 COMMENTS

  1. ” Human sex-determining chromosomes: X chromosome (left) and the much smaller Y chromosome. “

    Not quite. The SRY region on the Y chromosome determines sex and only the male sex is actually determined.

    ” Human Y chromosome much older than previously thought “

    Also misleading. The LINAGE of the Y is much older than we thought which is why scientific thinking is always tentative.

    Still, the pre-modern human origin raises interesting questions about the 70 or so genes still active and uncrossed on this chromosome.

  2. NeoD- Help me out here. Your line about the lineage of Y has me a bit confused. The way I read it, the human Y predates humans by more than previously thought. I found this no more remarkable than, say, fingers and toes predate humans, other than it might fill in a branch or two of the big tree.

    Did you read it as humans are older than previously thought? I am here to learn and my background on this subject is limited to an on-line course from Duke and the lectures of Richard, PZ, Eugenie, et al.

    Thanks in advance. While I am not a complete Luddite on this, I am at the point of just knowing enough to be a danger to the mind of my grandchild.

    • In reply to #2 by rjohn19:

      NeoD- Help me out here. Your line about the lineage of Y has me a bit confused. The way I read it, the human Y predates humans by more than previously thought. I found this no more remarkable than, say, fingers and toes predate humans, other than it might fill in a branch or two of the big tree.

      Did you read it as humans are older than previously thought? I am here to learn and my background on this subject is limited to an on-line course from Duke and the lectures of Richard, PZ, Eugenie, et al.

      Thanks in advance. While I am not a complete Luddite on this, I am at the point of just knowing enough to be a danger to the mind of my grandchild.

      ” Human Y chromosome much older than previously thought “

      This implies the Y chromosome itself and just not the proto human and human Y chromosome line, inherited from some restricted population of ancestors, is older than we previously thought. So, humans are not older than thought, but the Y chromosome line that many of us exhibit started with some remoter ancestor(s). Naturally Y chromosome predate humans, but the sentence is about humans.

      A subtle point and possibly not worth making.

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