Ok, I'll get the hang of these postings yet! To continue with the topic of bipedalism research that humbug talks aobut, part of my recent research has been to examine SIDS (Sudden Infant Death Syndrome) in light of the co-sleeping argument (that is, whether the arguments made by 'parenting experts' in magazines against co-sleeping with one's children as dangerous is valid). In order to understand the issues, many factors must be considered particularly birthing histories in primate lineage and cultural practices of co-sleeping. All this aside, one must consider the evolutionary data for birthing in humans. SIDS research has not recognized that human infants have an evolutionary past and have focused on uraban and industrialized areas.Originally posted by humbug:
Lets take a trait like bipedalism. The advantages of bipedalism are huge (hunting, gathering, building, etc) which points to natural selection. A GREAT deal of research has been done tracing the development of bidedal locomotion in our species. Turns out bipedalism requires many (too numerous to enumerate here) anatomical changes versus say a quadraped. A larger brain, smaller upturned pelvis, larger birth canal, completely different feet and leg structure. Scientists can trace OUR bipedalism back to our quadrapedal ancestors including all of the "transitional" forms.
The consequence of bipedalism in Australopithecus afarensis and subsequently Homo erectus is that offspring are born more neurologically immature in that most of their development takes place postnatally. Let me explain. In order to transition from quadrapedal to bipedal locomotion, the pelvis must broaden and rotate forward which then diminishes the size of the birth canal. Thus the postnatal care for human infants is greater than that of other primates.
So humbug you are absolutely right on (except that human birth canals have become narrower to accommodate our upright motion). There are other important factors in this research, both biological and sociocultural. But the point is that even though there are gaps in evolutionary data (anthropology/biology is not perfect but continued learning and more knowledge gained as a result of increased research) does not mean that the evidence is not there.
