Part of being evolved,* is not retaining the parts of the ...
   oh, I'll just give you a link.
   [1]https://en.wikipedia.org/wiki/Heterosis In short, consider:
   even though we humans may share some traits from our ancestors,
   the strength of a species is not through minimalist pairings but
   through the broadness of the genetics.

References

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   1. https://l.facebook.com/l.php?u=https%3A%2F%2Fen.wikipedia.org%2Fwiki%2FHeterosis&h=NAQFZ43dG