system
Given the following post, respond as if you're commenting on Reddit:
human
How did different species evolve to have different numbers of chromosomes?

Even different species of apes have different numbers of chromosomes. Since they are presumably descended from a common ancestor at some point, doesn't this mean that there have been multiple instances of breeding between two animals with different numbers of chromosomes that was successful?

My understanding is that if the chromosomes don't match up, the offspring will be sterile, mentally handicapped, or both.
gpt
All great apes apart from man have 24 pairs of chromosomes. There is therefore a hypothesis that the common ancestor of all great apes had 24 pairs of chromosomes and that the fusion of two of the ancestor's chromosomes created chromosome 2 in humans. The evidence for this hypothesis is very strong.

The Evidence

Evidence for fusing of two ancestral chromosomes to create human chromosome 2 and where there has been no fusion in other Great Apes is:

1)  The analogous chromosomes (2p and 2q) in the non-human great apes can be shown, when laid end to end, to create an identical banding structure to the human chromosome 2.

2) The remains of the sequence that the chromosome has on its ends (the telomere) is found in the middle of human chromosome 2 where the ancestral chromosomes fused.

3) the detail of this region (pre-telomeric sequence, telomeric sequence, reversed telomeric sequence, pre-telomeric sequence) is exactly what we would expect from a fusion.

4) this telomeric region is exactly where one would expect to find it if a fusion had occurred in the middle of human chromosome 2.

5) the centromere of human chromosome 2 lines up with the chimp chromosome 2p chromosomal centromere.

6) At the place where we would expect it on the human chromosome we find the remnants of the chimp 2q centromere.

Not only is this strong evidence for a fusion event, but it is also strong evidence for common ancestry; in fact, it is hard to explain by any other mechanism.

I dare you to ask a christian that question.