Hobbits small brains not so anomolous

Is the Hobbit's Brain Unfeasibly Small?:

Brain expansion began early in primate evolution and has occurred in all major groups, suggesting a strong selective advantage to increased brainpower in most primate lineages. Despite this overall trend, however, Mundy and his colleagues have identified several branches/lineages within each major group that have shown decreasing brain and body mass as they evolve, for example in marmosets and mouse lemurs.

According to Mundy, "We find that, under reasonable assumptions, the reduction in brain size during the evolution of Homo floresiensis is not unusual in comparison to these other primates. Along with other recent studies on the effects of 'island dwarfism' in other mammals, these results support the hypothesis that the small brain of Homo floresiensis was adapted to local ecological conditions on Flores."

The paper will show up in BMC Biology at some point. The main question I have is in regards to the purported tool use of the Hobbits. I can believe that a local adaptation toward small brains, Idiocracy-writ large, occurred. Brains are metabolically expensive, and it isn't as if the history of life on earth has shown the massive long-term benefits of being highly encephalized (though I think one can make a case that there has been a modest trend, with primates, and especially H. sapiens as extreme outliers above the trend). But could small brained creatures maintain the relatively advanced toolkit which the Hobbit finds have been associated with? Seems to me that there's a high probability here of some sort of contamination, but I'll be happy to be put in my place by anthropologists in-the-know....

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Also, I think Harpending/Cochran hypothesized that tool making was an instinctive behavior. If so, might not a shrinking brain nevertheless likely retain such a useful instinct, like nest building among birds?

How does the size of the hobbit's brain compare to that of, say, a 4 year old human child? I can remember being a (very verbal) 4 year old and intensely focusing on figuring out how a toy worked, or untying a complicated knot, and other stuff like that. It hardly seems implausible to me that, given some additional body strength and manual dexterity, someone with a brain no larger than a 4 year old human could make fairly sophisticated tools. Maybe the brain would have to be tweaked a little, but I don't see that it would have to be anything radical.

One could imagine that it requires a larger brain to develop tools and tool use, but maybe not such a big one to maintain it.

Crows, with brains the size of walnuts, make tools. Chimps with much larger brains make tools of about the same complexity as crows. The human brain seems overdesigned if the only thing it is used for is tool making (obviously not). How long were the hobbits isolated on Flores, and how long prior was tool making in their linage?

Plenty of time for brains to become reduced in size yet allow tool making to be retained. I speculate that our much larger brains allow us to imagine more complex tools and then create them. In terms of the physical dexterity needed to handle raw materials, not so much difference.

What has always fascinated me is the sheer genius the original tool creators must have had, to begin the cracking of rocks to form sharp edges, and with their tiny little brains.

"was adapted to local ecological conditions on Flores"

I wonder if the areas of the brain itself also had specific adaptations. For instance, the Aborigines have a larger visual cortex area. This is thought to possibly represent an adaptation to living conditions in the bush and desert regions of Australia.


By Blumenthal (not verified) on 27 Jan 2010 #permalink

It's not just an issue of "maintaining" advanced tools - some are suggesting the hobbits are from a pre H. sapiens line that never developed tool use as sophisticated. Combining much smaller brains with much more sophisticated tools sounds pretty iffy to me.

Then there's the contrary point in Comment #1....

Since Homo erectus has been found there dating much, much earlier than floresiensis, could the tools have been created by H. erectus and used by floresiensis? How long does a hand axe last? Were there scraps in Liang Bua that would indicate creating the tools?

By thunder_puck (not verified) on 30 Jan 2010 #permalink