Y Chromosome Adam is a parallel to
Mitochondrial Eve. Just as
mitochondria are inherited solely from mothers, the Y chromosome is
inherited solely from fathers. The difference is that only males get
the Y chromosomes, but both males and females get mitochondria.
Interestingly, studies have been done on this subject. In
Absence of Polymorphism at the ZFY Locus on the Human Y Chromosome,
as indicated by its title, it was found that 38 males from all over the
world had very little, or no* variance in a portion of
the Y chromosome. The conclusion was that humanity has a common, single, ancestor
absolutely no earlier than 270 000 years ago, otherwise we would have variance.
Here are some possible interpretations of this study (not all of them, by any means):
- "Adam"'s Y chromosome spread throughout and dominated an existing human population.
This would happen if the quantity of males who were not male-descendants of "Adam" decreased
to nothing.
- Sometime between 270 000 BC and now there was a major (enough emphasis?)
population
crash, and only one male's family survived. Keeping with the theme, we could also call this
guy "Y Chromosome Noah". :-)
- The calculation method's logic is flawed, although I am uncertain on what grounds.
- Humans were created, not evolved. I said possible interpretations, so
don't downvote me for being encompassing.
Or some combination of these interpretations would work as well.
Another study done similarly has placed Y Chromosome Adam at maximum 188 000 years ago, and
yet another at a recent 49 000.
* This is uncertainty on my part. I am only reporting the studies
second hand. The information comes from the following URL (about half way down):
http://www.reasons.org/resources/apologetics/humanevolution.html
You may want to read the shorter http://reasons.org/resources/apologetics/chromosome.html.