In Praise of the Pelvis

In human paleontology there is a tendency to concentrate attention on the skull. This is understandable since the skull is often mostly what is left to identify a particular homonid.

And, like Disney with animals, we tend to anthropomorphize bones and to look most kindly on those parts which most closely resemble our notions of self.

In the evolutionary record of vertebrates, the transition of the pelvis is of singular importance.

From open to closed represents a step between the reptile, birds, and non-eutherian mammals ; to the true placental mammal.

I suggest that the the translation of the eutherian pelvis between H.erectus and H.sapiens resulted in those qualities which we most associate with "human" : cognition , language, and an emphasis on Sexual Selection.

A synopsis of this evolution is found by looking at the last "step" : from marsupials to eutherians .

The epipubic bones were described by Huxley and help to identify the marsupial. Huxley, however, allowed these structures to drop away when he closed the marsupial's pelvis and revealed the eutherian.

I suggest that the epipubics went with the new eutherians; as the "os penis" or baculum. This testosterone-dependent structure is connected by it's related soft tissues to the "pelvic symphysis" which is that place where the joining of the pelvic ring is made complete.

The female homolog, without calcification, is part of the clitoris just as the "os penis" is part of the penis.

The configuration of this structure in most female eutherians includes "vestibular bulbs" and I suggest that it is these bulbs which give rise, during ovulation, of that peculiar eutherian trait of estrus. For reasons related to hormonal chemistry, this unique behavior is a product of a mechanical process, rather than entirely chemical.

In women, as in gibbons and tarsiers, the "vestibular bulbs" are positioned so as to negate this mechanical effect, which leaves these creatures - and us - free of estrus.

This freedom from the compulsive behavior of the mammal-in-heat allows the female to resume the mating behavior characteristic of the other vertebrates.

These include the use of vocal courtship by the male and other aspects of the Female Choice form of pure Darwinian Sexual Selection.

I have abbreviated much of the source reasoning of this hypothesis, in view of the nature of this forum.

best regards
arne