One of the most interesting features of our chromosomes, which I mention briefly in the article, is that we’re one pair short. In other words, we humans have 23 pairs of chromosomes, while other apes have 24.
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The fusion of chromosome 2 millions of years ago may not have caused any big change in hominid biology—except, perhaps, by making it difficult for populations of hominids with 23 pairs of chromosomes to mate with populations who still had 24.