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timtyler comments on [LINK] On the unlikelihood of intelligent life - Less Wrong Discussion

7 Post author: NancyLebovitz 27 March 2013 05:29AM

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Comment author: timtyler 30 March 2013 10:59:39AM *  0 points [-]

Ants then. They are 6% brain, which easily trumps humans in terms of EQ.

The idea that there's no trend towards bigger brains seems stupid. Almost as stupid as the idea that we should expect of see such a trend in all organisms.

All modern organisms evolved from bacteria-like critters, with little nervous tissue. Of course there's a trend towards bigger brains. The only issue is why - and that seems pretty obvious too: brains pay.

Comment author: CellBioGuy 09 May 2013 05:37:53AM 2 points [-]

A random walk away from no brain by a large number of lineages would also give you a constantly increasing upper bound on brain size.

Comment author: timtyler 09 May 2013 11:57:28PM 1 point [-]

That was S. J. Gould's model - in Life's Grandeur. Assuming that a trait like brain size behaves as though it is a neutral trait seems pretty loopy, though. Now we have enormous data centres to explain, the "random drift" model is surely no longer worth entertaining.

Comment author: Nornagest 30 March 2013 06:07:52PM *  2 points [-]

Ants then. They are 6% brain, which easily trumps humans in terms of EQ.

That doesn't fly either, I'm afraid. EQ is not a straight brain-to-body-mass ratio; the expected brain mass in the formula scales sublinearly against body mass, giving smaller animals a tendency to have proportionally larger brains. This is motivated by the fact that some nervous functions (diaphragm contraction, for example) are relatively constant in complexity but still have to be handled by small animals' brains, so the smaller an animal is the more nervous overhead it has to deal with.

The formula this works from was only designed to apply to mammals; different body plans have different neural requirements, and arthropod nervous systems are very different from mammalian. If we ignore that and apply the mammalian formula Ew(brain) = 0.12w(body)^0.66 to something ant-sized, it gives us an expected brain mass of about three milligrams for an ant weighing four milligrams (obviously absurd, but we knew the formula was bogus) and an encephalization quotient of about 0.08 if your 6% value is accurate. Human EQ is about 7.5.