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.