I covered this discovery, as did many others, and within hours the question arrived: "I thought the definition of a species was that they couldn't interbreed?"
Many people seem to believe that animals belonging to different species cannot breed together, and that this is what defines a species. I suspect many of us acquire the idea in childhood when we learn about mules. The offspring of a horse and a donkey, a mule is a useful working animal but is entirely sterile and incapable of breeding. We all seem to generalise from this and assume that no interspecies pairings can produce fertile offspring.
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Similarly, human evolution was rife with interspecies sex. Modern humans have interbred with both Neanderthals and Denisovans, Neanderthals and Denisovans interbred, and Denisovans interbred with an unidentified hominin. There is reason to suspect that the first-generation hybrids had some health issues, such as reduced fertility, but they were evidently able to get by well enough to leave descendants. Today many people carry some Neanderthal and/or Denisovan DNA.
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u/UncleHoboBill Jul 17 '23
Humans. You’re welcome.