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stickymaplesyrup t1_j50nlvg wrote

Reply to comment by suvlub in Given that reproduction is difficult or impossible when both animals have different numbers of chromosomes, how did so many species evolve to have so many different numbers of them? by MercurioLeCher

Okay, hear me out.

One of the ways we define whether or not species are different is if they can reproduce together, and if the offspring are also able to reproduce. This is why horses and donkeys are still different species even though they can have babies, ie mules, because mules are sterile.

What if these 44 chromosome people grew in number and could have kids together (non-incestuously, I don't know if there are multiple families with this condition)? And then those kids could have kids, and so on.

Would this be the origin of a new species of human?

It's fun to think about and consider.

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ohheyitslaila t1_j515r2u wrote

You actually picked a really interesting set of animals for your example!!! I apologize if I explain anything poorly, I just know a little about this stuff because my family breeds horses. I feel like this kind of hits on what you’re asking.

So female horses and male donkeys can be bred to each other, that produces mules. Female mules have 63 chromosomes, which can’t usually be split evenly to produce a fertile egg. BUT, some female mules actually produce an egg that does have an even set of chromosomes. It’s just that the egg rarely meets up with a sperm with a matching set of chromosomes. A case of this incredible, one in a million chance did occur and a female mule gave birth to a male foal in 2007. The foal had some deformities, believed to be caused by the chromosomal issues, specifically a problem with its legs. But it lived until about 2010, when it slipped on ice and was badly injured, leading to him being humanely euthanized.

I wonder if that kind of thing could happen in humans. It would probably be just as rare, if not more so.

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