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Starch and human evolution

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clayto
Posts: 384
Joined: July 22nd, 2007, 6:34 pm

Starch and human evolution

#1 Post by clayto » September 22nd, 2007, 8:27 pm

There is a link to a BBC article on scientific research into the importance of starch, rather than meat, in human evolution ----- in the Humanist Vegetarian Forum.

Chris
clayto

Tom Rees
Posts: 29
Joined: September 8th, 2007, 8:43 pm

Re: Starch and human evolution

#2 Post by Tom Rees » September 23rd, 2007, 9:15 pm

clayto wrote:There is a link to a BBC article on scientific research into the importance of starch, rather than meat, in human evolution ----- in the Humanist Vegetarian Forum.

Chris
The science itself is very interesting but the headline-grabbing 'speculation' seems to me to based on a misunderstanding of evolution. The gist of it is this:

And these extra calories may have been crucial for feeding the larger brains of humans, speculate the University of California Santa Cruz authors.

But the thing is, if an abundant and easy-to-obtain source of calories becomes available, you'd expect brain size to decrease rather than increase. Why invest all those calories in a brain, when you have more than enough food and you could invest them in something else like faster reproduction?

In other words, what limits brain development is not a shortage of nutrition, but a shortage of benefit. Because we're brainy, we're inclined to believe that having a big brain is an evolutionarily optimal strategy, but it usually isn't. The limit on brain development in other animals is not that they're short of food, but rather that bigger brained animals are usually less evolutionarily fit.

For example, at some stage in the past ruminants developed secondary fermentation. But they didn't use the calorie bonanza to develop big brains. Rather they used it to become more numerous.

The trigger for brain development in humans is now widely accepted to be bipedalism. When our ancestors came down from the trees to the savannah, it left us with a pair of useful hands - which meant that a brain had a value that wasn't there for other species. And so a bigger brain developed. Different hominins had different dietary strategies (Neanderthals being notable for an almost carnivorous diet, for example), but they all had increasingly larger brains.

When you look at what they've actually shown, it has no bearing on the brain development issue. They've shown that 1) copies of amylase vary among races, depending on how much starch there is in our diet. 2) Early hominins probably ate starchy tubers. What this says to me is that the transition to the savanna was linked to a dietary shift from fruits and occasional meat, to tubers and occasional meat.

This bit raised my hackles:

“To think that, two to four million years ago, a small-brained, awkwardly bipedal animal could efficiently acquire meat, even by scavenging, just doesn't make a whole lot of sense.”

You wouldn't say that if you've ever watched footage of chimps hunting - especially that footage earlier this year of using spears to hunt bush babies.

My conclusion: this is a nice piece of science that sheds some interesting light on early hominin evolution, overlaid with some irrelevant cock-and-bull about how it somehow explains brain enlargement!
:angry:

clayto
Posts: 384
Joined: July 22nd, 2007, 6:34 pm

Starch

#3 Post by clayto » September 24th, 2007, 8:26 pm

Thanks for this response. I will pass it on to Stephen of the HVG as he has a particular interest and knoweldge (much more than mine) of evolution and should find both items of interest. :thumbsup:
clayto

Tom Rees
Posts: 29
Joined: September 8th, 2007, 8:43 pm

Re: Starch

#4 Post by Tom Rees » September 25th, 2007, 2:28 pm

clayto wrote:Thanks for this response. I will pass it on to Stephen of the HVG as he has a particular interest and knoweldge (much more than mine) of evolution and should find both items of interest. :thumbsup:
Hi Chris, bring him along to the forum! I tried tracking down some proper science on human brain evolution on the web but couldn't find much.

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