Scientific American resets my priorities (or at least my metaphors) with anthropological research. You think in order to walk, you gotta crawl first? Not really:
According to anthropologist David Tracer of the University of Colorado at Boulder, babies of the Au hunter-gatherers of Papua New Guinea do not go through a crawling stage. Instead their parents and other caregivers carry them until they can walk. Yet Au children do not appear to suffer any ill effects from skipping this phase. In a presentation given to the American Association of Physical Anthropologists in Chicago this past April, Tracer argued that, in fact, not crawling may be entirely normal and possibly even adaptive.
…Citing a study of Bangladeshi children showing that crawling significantly increases the risk of contracting diarrhea, Tracer proposes that carrying infants limits their exposure to ground pathogens. It also protects them from predators. He therefore contends that the crawling stage is a recent invention….