Department of Evolutionary Biology, Unit for Theoretical Biology, University of Vienna, Vienna, Austria.
Konrad Lorenz Institute for Evolution and Cognition Research, Klosterneuburg, Austria.
Nat Ecol Evol. 2021 May;5(5):625-630. doi: 10.1038/s41559-021-01425-z. Epub 2021 Mar 25.
It is commonly assumed that the strong sexual dimorphism of the human pelvis evolved for delivering the relatively large human foetuses. Here we compare pelvic sex differences across modern humans and chimpanzees using a comprehensive geometric morphometric approach. Even though the magnitude of sex differences in pelvis shape was two times larger in humans than in chimpanzees, we found that the pattern is almost identical in the two species. We conclude that this pattern of pelvic sex differences did not evolve de novo in modern humans and must have been present in the common ancestor of humans and chimpanzees, and thus also in the extinct Homo species. We further suggest that this shared pattern was already present in early mammals and propose a hypothesis of facilitated variation as an explanation: the conserved mammalian endocrine system strongly constrains the evolution of the pattern of pelvic differences but enables rapid evolutionary change of the magnitude of sexual dimorphism, which in turn facilitated the rapid increase in hominin brain size.
人们普遍认为，人类骨盆的强烈性别二态性是为了生育相对较大的人类胎儿而进化的。在这里，我们使用全面的几何形态测量方法比较了现代人类和黑猩猩的骨盆性别差异。尽管人类骨盆形状的性别差异幅度是黑猩猩的两倍，但我们发现这两种物种的模式几乎相同。我们得出的结论是，这种骨盆性别差异模式并非在现代人类中从头进化而来，而必须存在于人类和黑猩猩的共同祖先中，因此也存在于已灭绝的 Homo 物种中。我们进一步提出，这种共同模式早在早期哺乳动物中就已经存在，并提出了一个便于变异的假说作为解释：保守的哺乳动物内分泌系统强烈限制了骨盆差异模式的进化，但允许性二态性幅度的快速进化变化，这反过来又促进了人类大脑尺寸的快速增加。
