John Hawks has an excellent post rebutting some misinformation and confusion on the part of Colin Blakemore, an Oxford neurobiologist. Blakemore asserts that:
* There was a sharp spike in cranial capacity ~200,000 years ago, on the order of 30%
* And, that the large brain was not deleterious despite its large caloric footprint (25% of our calories service the brain) because the “environment of early humans was so clement and rich in resources”
Hawks refutes the first by simply reposting the chart the above (x axis = years before present, y axis = cranial capacity). It’s rather straightforward, I don’t know the paleoanthropology with any great depth, but the gradual rise in hominin cranial capacity has always been a “mystery” waiting to be solved (see Grooming, Gossip, and the Evolution of Language and The Mating Mind: How Sexual Choice Shaped the Evolution of Human Nature). Blakemore may have new data, but as they say, “bring it.” Until then the consensus is what it is (the hominins with the greatest cranial capacities for what it’s worth were Neandertals, and even anatomically modern humans have tended toward smaller cranial capacities since the end of the last Ice Age along with a general trend toward smaller size).
But the second issue is particularly confusing, as Blakemore should have taken an ecology course at some point in his eduction if he’s a biologist (though perhaps not). One of the problems that I often have with biologists is that they are exceedingly Malthusian in their thinking, and so have a difficult time internalizing the contemporary realities of post-Malthusian economics (see Knowledge and the Wealth of Nations: A Story of Economic Discovery).Innovation and economic growth combined with declining population growth have changed the game in fundamental ways. And yet still the biological predisposition to think in Malthusian terms is correct for our species for almost its whole history.*
A “tropical paradise” is only a tropical paradise if you have a modicum of affluence, leisure, and, modern medicine. Easter Island is to a great extent a reductio ad absurdum of pre-modern man and gifted with a clement regime. Easter Island’s weather is mild, the monthly low is 18/65 °C/°F and the monthly high is 28/82 °C/°F. The rainfall is 1,118/44 mm/in. But constrained on an island the original Polynesians famously transformed it into a Malthusian case-study. We literally breed up to the limits of growth, squeezing ourselves against the margins of subsistence.
I can think of only one way in which Blakemore’s thesis that the environment of early humans was rich in resources might hold, at least on a per capita basis: the anatomically modern humans of Africa exhibited bourgeois values and had low time preference. In other words, their population was always kept below ecological carrying capacity through forethought and social planning, since there is no evidence for much technological innovation which would have resulted in economic growth to generate surplus. My main qualm with this thesis is that it seems to put the cart before the horse, since one presupposes that a robust modern cognitive capacity is usually necessary for this sort of behavior.
* Malthus’ biggest mistake was probably that he did not anticipate the demographic transition, whereby gains in economic growth were not absorbed by gains in population.
Razib Khan’s degrees are in biochemistry and biology. He has blogged about genetics since 2002, previously worked in software development, is an Unz Foundation Junior Fellow and lives in the western US. He loves habaneros.
March 29th, 2010 at 5:16 pm
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March 29th, 2010 at 7:46 pm
Right, Neandertals had an average cranial capacity of 1450 cc, besting our average brain size of 1350 cc. As Neandertals were becoming distinct from Homo heidelbergensis 300,00-250,000 years ago, that doesn’t seem to fit with the sudden spike in cranial capacity 200 kyr that Blakemore asserts.
But wait, Heidelbergensis skulls (Atapuerca SH 4) have been found as large as 1390 cc, dating from the middle Pleistocene. That pushes back large brains as far back 500 kyr.
To be fair, Heidelbergensis had an average cranial size of around 1200 cc, about 90% that of a modern human. So from the middle Pleistocene to the present day we’ve seen an increase in cranial capacity of about 10%.
Seems gradual to me, not counting the decline in hominan brain size after the demise of the Neandertals, of course. Perhaps Blakemore was boasting of his own large organ?
March 30th, 2010 at 12:59 am
Surely Malthus was incorrect on all counts – he predicted the population would reach capacity in 1890. Ahem, and yet we are still here. He also recommended that the poor are killed to save resources. Not so right either.
http://overpopulationisamyth.com/
March 30th, 2010 at 1:16 am
did you bother to read the post?
And yet still the biological predisposition to think in Malthusian terms is correct for our species for almost its whole history
in any case, yes, malthus was wrong in most of his predictions and prescriptions. what i’m alluding to the fact is that nature is malthusian, and most of human history has been malthusian. blakemore seems to have forgotten this conjuring images of tropical idyll.
March 30th, 2010 at 4:40 am
I saw Blakemore present on his theory at the Hinxton campus a couple of weeks ago. Most of his talk was innocuous material about neuronal plasticity, and the evolution part was crammed into a couple of slides at the end (despite being the headline for his presentation).
Afterwards there was an embarrassed silence from the human evolutionary geneticists in the audience: Blakemore is an excellent neurobiologist, but his understanding of evolutionary theory is simply cartoonish.
March 30th, 2010 at 6:19 am
Sigh. I’m becoming careerist, because I don’t really care about all the ways he’s wrong, just how he and his ilk are in my way. Academia is filled with illustrious Blakemores. Tenured poobahs with their best work two or more decades behind them, bored with their small ponds, using their prominence to make authoritative pronouncements outside their narrow expertise and getting taken seriously (by some), looking stupid to the rest of us. Postdocs need their jobs. People with good, creative ideas need their grant money.
April 1st, 2010 at 5:42 am
you know, looking at the graph, I do see a faster rate of increase beginning around 200kya – whether I’d call it ‘sharp’ is another question.
April 4th, 2010 at 7:44 am
[...] Khan – “Thomas Malthus Was Right. Mostly“, “Again, Malthus Was Right (In the [...]
April 4th, 2010 at 11:16 pm
[...] week ago I pointed to a controversy about the rate of growth of human cranial capacities over the past few million years. I asserted [...]