How is it that Dalmatians and Chihuahuas are so different but are members of the same species, yet two sparrows that look nearly identical are different species?
In: Biology
Because how things look is a bad indicator of how related things are. Modern genetic knowledge has changed, and continues to change, the family trees we’ve drawn based on purely physical traits.
In the case of dogs, we’ve selectively bred them extremely rapidly, but the genes that control body size or leg length don’t make sperms and eggs incompatible. 20,000 years isn’t enough time for regular genetic drift to give different breeds different # of chromosomes or something. And, breeds aren’t exactly completely separate populations. Regularly getting gene pool infusions from other breeds keeps massive genetic differences from building up.
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