ZHD comments on New report: Intelligence Explosion Microeconomics - Less Wrong

45 Post author: Eliezer_Yudkowsky 29 April 2013 11:14PM

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Comment author: ZHD 30 April 2013 06:56:37AM *  3 points [-]

Hominid brain size has not been increasing for at least the past 100,000 years. In fact, the range is tighter and median is lower for homo sapiens vs homo neanderthalensis.

Given that information, how does this change your explanation of your data?

The most important brain developments in the genus have come during the time when brain size was not increasing. This means that size can not be an explanatory variable.

Cheers, ZHD

Comment author: CarlShulman 30 April 2013 08:17:59AM *  3 points [-]

Footnote 44 discusses Neanderthals having larger brains, so it's not new data.

Comment author: ZHD 30 April 2013 08:25:06AM 0 points [-]

Thank you Carl. I am having some difficulty navigating to that discussion. Can you provide a direct link?

Comment author: CarlShulman 30 April 2013 08:27:08AM 1 point [-]

It's the link at the top of the OP. Look on page 38 of the document (page numbers are at the bottom) to find footnote 44.

Comment author: ZHD 30 April 2013 09:00:48AM 5 points [-]

Thanks for the help!

So this is the footnote:

  1. Neanderthals may have had larger brains than modern humans (Ponce de León et al. 2008) and it is an open question how much Neanderthals interbred with the ancestors of modern humans. It is possible that the marginal fitness returns on cognition have leveled off sharply enough that improvements in cognitive efficiency have shifted the total resource cost of brains downward rather than upward over very recent history. If true, this is not the same as Homo sapiens sapiens becoming stupider or even staying the same intelligence. But it does imply that either marginal fitness returns on cognition or marginal cognitive returns on brain scaling have leveled off significantly compared to earlier evolutionary history

That appears to be circular reasoning. It only implies that "marginal fitness return on cognition" has leveled off if we define fitness as a function of brain size—we have no fitness measurement otherwise.

My previous suggestion, that the most important brain developments in our genus are independent of brain size, needs an explanation with a much different anchor.

Comment author: pcm 11 May 2013 07:30:12PM 1 point [-]

There is speculation that brain size decreased due to loss of olfactory and maybe other sensory parts of the brain after dogs took over those functions. See here.

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