The Chromosome that Broke the Camel’s Back

I’ve been asked what the tipping point was for me to accept the Theory of Evolution after resisting it for most of my life. As I researched, the weight of the evidence was cumulative, so the fact that flipped the switch for me was more a function of timing and the order I just happened to have discovered things, as opposed to necessarily the strongest or best argument. That said, I do happen to remember what it was.

(Quick aside: I’m aware that millions of people around the world accept science like evolution, geology, cosmology, paleontology and the big bang while at the same time believing in a God. In fact, this is the official position of the Catholic church. This is one reason I will be attempting to keep discussion of science and religion separate on my blog when the topic doesn’t require conflation.)

Humans have 23 pairs of chromosomes, while all the other great apes have 24 pairs. If evolution proposes that apes and humans share a common ancestor, this difference must be explained. It was hypothesized that a mutation fused two of the ape chromosomes creating just one in humans. And that is what modern genetics has found.

In 2005, a paper was published comprehensively identifying where two analogous chromosomes of the non-human great apes fused end-to-end to create human chromosome 2. Our chromosome has end markers (the telomere) in the middle, and two middle-sequences (centromeres) laid out in the pattern that is consistent which such fusing. The first centromere of human chromosome 2 lines up with chimp chromosome 2p, while the second centromere matches chimp 2q.

I’m not a geneticist. The last time I was in a formal biology class, the technology to sequence these genes was a far-off science-fiction dream. So rather than embarrass myself further, I’d point you to this short video that explains the finding much better than I could.


This initial finding has been corroborated by significant research in the years since.

If you are feeling curious and ambitious, I would encourage you to dig deeper into the science yourself, as I did. Much of it is over my head, but it was enough to conclusively convince me that our chromosome 2 is a fusion of two common ancestor’s chromosomes. (And amazed me at what has happened in the field of genetics while I was off marketing space movies.) The evidence is difficult to explain by any other mechanism.

I was so convinced, I named this blog after it.

As you research this yourself, you may also find amateur authors attempting to use jargon to paint minor cherry-picked disagreements (some since settled) among geneticists about the “how” this happened as some kind of scientific doubt about the “what” happened. I find this trend unfortunate, as scientists publicly refining the work of other scientists is what gives science its power, not its weakness.

One thought on “The Chromosome that Broke the Camel’s Back

  1. While you were “marketing space movies” I was trying to build databases and web apps for the guys who were figuring this stuff out- and my mind was blown regularly by the intricacies of biology. The father you go down the rabbit hole, the more complex (and amazing) it gets!

    Liked by 1 person

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