If you read about the various famines in the last 60 years, you'll find that one of the big
reasons why some underdeveloped countries have them so frequently is that they are
too dependent on one or two
staples(usually poor foods such as tubers, like cassava etc- cassava contains cyanogenic
compunds so must be fermented, grated and left out in the sun so that the cyanide can
evaporate, it also needs to be cooked beforehand, and has been linked to the deficiency-
disease kwashiorkor.) The trouble with tubers is
that they commonly have antinutrients in them, and are deficient in a number of key
trace nutrients, so become a problem if consumed in more than trace amounts. The other
point is that the DHA hypothesis holds that it's the DHA in meat that helps to increase
brain-size(tubers don't contain DHA in remotely significant amounts, last I checked).
As far as cooking is concerned, it's already been pointed out that the average hominid
brain-size heavily expanded in size long before cooking was ever invented, so there's
clearly no link between cooking and brain-size - for that matter, there wasn't that much
difference in brain-size between archaic homo sapiens(of around 300,000 years ago) and
Modern Man, whereas the difference in brain-size between Homo Erectus and modern
man or between Homo Australopithecus and Home Erectus was pretty large - so if one
were to take the line that absolutely all current dietary habits re cooking or whatever
were directly related
to greater brain-size , then that would imply that eating raw meat was far more effective
than eating any cooked-food(meats or tubers) as regards increasing the average hominid
brain-size.
At any rate, as www.beyondveg.com pointed out, our Neolithic ancestors greatly
increased their intake of starchy foods, yet their average brain-size(by comparison to
their Palaeo ancestors) actually decreased in tandem with this practice(by c. 8%), thus
appearing to indicate that eating tubers actually decreases brain-size.
Geoff
Why famine only? Tubers are a high energy density food. They are not unduly difficult to
gather. The Expensive Tissue hypothesis, which I accept, stipulates that the evolutionary
decrease in the gut-brain ratio depends on a higher density diet. I believe meat must
have dominated but I don't see any reason to suppose it did so to the exclusion of other
high density foods, such as tubers. Moreover, the fact that cooking shows up about
25-50,000 years before homo sapiens, but a long time before the Neolithic, is at least
suggestive. I understand that paleolithic tubers would have been pretty gnarly in
comparison with modern selectively bred mega-starches but I just don't see any reason to
think that paleo people ignored them.
|