Humans have 23 pairs of chromosomes. In contrast, chimpanzees have 24 pairs of chromosomes and lack any pair resembling the long human chromosome 2 pair; instead, chimpanzees have two pairs of medium-sized chromosomes. What is the most likely explanation for these differences in the human and chimpanzee genomes?
A) The common ancestor of humans and chimpanzees had 24 pairs of chromosomes, and at some point in the human lineage, two chromosomes fused end to end, providing some selective advantage.B) The common ancestor of humans and chimpanzees had 23 pairs of chromosomes, but when chimpanzees evolved, one of the chromosomes broke in half.C) At some point in evolution, human ancestors and chimpanzee ancestors were able to mate and produce fertile offspring, making a new species.D) Chromosome breakage resulted in additional centromeres being made, allowing meiosis to proceed successfully.E) Transposable elements transferred significantly large segments of the chromosomes to new locations.

The common ancestor of humans and chimpanzees had 24 pairs of chromosomes, and at some point in the human lineage, two chromosomes fused end to end, providing some selective advantage.

Scientists have proved that the reason why humans have 23 chromosomes and chimpanzees have 24 is that there was an end-to-end fusion of two ancestral chromosomes resulting 1 and it is believed that this fusion conferred in man certain obvious advantages over the chimpanzees.