There is an interesting principle in biology, named Haeckel’s Recapitulation Theory: ontogeny recapitulates phylogeny. In simple terms, that means that you can read the whole evolutionary tree leading to a species just by looking at successive development stages of the fetus. We start looking like single-cell individuals, “evolve” into bunches of cells, eventually “turn” into fish, then lizards, then monkeys, etc.
It’s not as simple as that, and the principle/theory has been refuted/rejected.
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