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There's at least one paper suggesting the reason for four limbs is because of the way embryos develop. Basically, an embryo's cells develop early on into three layers: ectoderm, mesoderm, and endo...
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There's at least one paper suggesting the reason for four limbs is because of the way embryos develop. Basically, an embryo's cells develop early on into three layers: ectoderm, mesoderm, and endo...