eli5 : how did different animals come from common ancestors

Question

eli5 : how did different animals come from common ancestors

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Answer 1

My siblings and I are different animals who all came from common ancestors. 🙂

I assume you mean different *species*. If some descendants end up living in a different environment from the others, then there will be a different set of environmental conditions that they’ll need to fit in order to continue reproducing. It’s not that the animals *absolutely can’t* survive in the new environment; it’s just that on large scales and over long periods of time, the individual animals who have traits that are especially favorable to that specific environment will be more successful than the rest. Eventually, those specific traits add up to an animal that can’t reproduce with other descendants of their common ancestor.