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czyivn t1_j51pj1j 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

Which perfectly explains why different species frequently have different numbers of chromosomes: It's part of how you get a new species.

Imagine a family of these 44 chromosome people dropped on a desert island with another family of 46 chromosome people. Breeding within a chromosome number group is likely to be more successful than outbreeding. Therefore, over time, a couple possibilities are likely.

  1. The two groups stop interbreeding much and instead carry on as two indepdendent groups which accumulate more independent mutations over time until they are completely infertile with each other.
  2. One of the two groups dies out.
  3. They heavily interbreed. This might result in both groups dying out if there aren't enough fertile individuals in successive generations.

Several scenarios could result, over time, with the emergence of a new population that's not interfertile with 46 chromosome humans. A new species.

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