It may be that not everyone understands the evidence you are referring to in this OP. I suggest that you explain briefly what is special about Chromosome #2, what telomeres are, etc. Then you can provide a link or two that explains it in more detail. Just a suggestion.
Thanks, SR. I did consider doing this, but
1) the OP was a bit long already
2) I was assuming those who had an answer had already considered the problem, so would know about it already
3) I'm no biologist so wouldn't be able to give the best summary
4) Wiki/Google, people! Seriously, do I have to do everything around here

5) I'm lazy
6) Oh, well, ok. It might aid some possible lurkers, so...
Humans have one pair fewer chromosomes than all the other Great Apes. This was trumpeted by creationists as an impossible sticking point for common descent, as an organism's offspring can't just miss an entire chromosome. But then science discovered something very interesting about Human Chromosome 2... The ends and middles of chromosomes are marked by "blobs" of genetic information called telomeres and centromeres (respectively), but Chr 2 has two centromeres and a "misplaced" telomere site in the middle (ie something like t---c---t---c---t). This is completely wrong for a normal chromosome, but exactly what you'd expect to see if two normal chromosomes fused end-to-end. Moreover, the two halves of this chromosome correspond very closely to two separate chromosomes in apes (2A & 2B -- used to be something else, can't remember the numbers -- EDIT: 12 & 13, apparently. Yay Google.). Therefore, it is very strong evidence that humans used to have the same chromosomes as the other apes, but they fused at some point in the past. That's evolution, and also evidence of common descent.
Wiki linkage:
http://en.wikipedia.org/wiki/Chromosome_2_%28human%29