And I’ve never seen anyone rationally debunk the quack claim that it makes delivery easier.

One possible way to drive secondary altriciality might be that caretaking for our primary neoteny requires longer education in childhood — to develop the sorts of skillsets that enable cultural support for complicated deliveries, for a mother/baby pair who can’t forage enough to feed themselves, etc. Greg/ Iain, I can’t remember enough of my Hrdy etc. to accurately report the state of the research here — is this a reasonable possibility?

I would not think that the baby sling is a different adaptation than altriciality. The “extended development” can be seen as a single big blob of an adaptation but it may well be multiple things, with multiple steps at distinctly different times. (Or not.) Most people would argue that the eye is a great adaptation, but it isn’t. It’s a whole shitload of adaptations.

I should also point out, and I’ll address this in more detail later, that what I’m saying here is not groundbreaking or new. Rather, some version of this is what everyone in the biz believes to some extent, and it is something that has not been reiterated on this blog for a while. We have been arguing about genetic vs. cultural adaptations, and I’m taking heat from people who really know very nothing about this sort of thing, for assuming that most aspects of most human behaviors are not mostly genetic. But, when we look at humans, it is reasonable to say that one of our most important adaptations is the non-genetic or non hardwired nature of our behaviors. We should be surprised to see shopping for shoes or watching football or making umlauts on things as variable across our species in a way that maps underlying allelic variation!

Nevertheless, the argument that infant carrying impacted hominin cognition was the foundation of the argument that Noble and I produced 21 years ago. The steps were that bipedalism made carrying necessary, and hairlessness made it obligatory. The dating of the first of these is not (much) in dispute, the dating of the second is agreed but not demonstrated. So obligatory infant carrying must indeed have been around 2.2 million years ago (with or without slings). And the impact was probably immediately observable in the amount of “encoding” in the brain outside the womb. This, we suggested, is the fundamental human adaptation.

Problem is that the timing of the apparently delayed brain growth (relative to chimpanzees) is difficult to date. There are actually two candidate dates–the early brain increase and the second brain increase about 400 thousand years ago. Arguably this also was a time of important behavioural changes that could be said to be consequent on infant learning.

I discuss some of these issues in my paper: Davidson, I. (2007), ”As large as you need and as small as you can’–implications of the brain size of Homo floresiensis’, in A. Schalley and D. Khlentzos (eds.), Mental states: evolution, function, nature (Amsterdam: John Benjamins), 35-42.

This can be found on my site: http://une-au.academia.edu/IainDavidson

We live in cultures complex enough to objectify the cultural significance of something like misplaced umlauts; it should not surprise anyone that it takes longer to develop. (And that made me lol in public, but is was very much to the point.) It’s my contention there is nothing we call human nature not addressed in some ways by cultures; even divergence from the central memes proceeds in reference to the original.

Another thing I wanted to add is that the fairly common meme comparing human early development with other species is certainly useful in an evolutionary biological context, but describing it as too long, or some other characterization implying that human development is defective in some way, just does not follow. I might as well point out that I am really, really old…in dog years. It’s human development, not bonobo development. It may be clumsy or inefficient in some senses, but the processes result in us, and if it had evolved differently you and I would almost certainly not be talking about it here and now.

/end pet peeve

Nice post.