How Well Does Evolution Explain Human Intelligence? 


In A Challenge To the Argument From Reason I wondered how evolution could produce such an extraordinary thing as human intelligence--it seems contrary to what evolution would predict. Jordan left a comment* in which he said the answer might be in a 2005 paper by Flinn et al. I recommend the paper to you for your greater understanding of evolutionary theory. 

Here is what I saw in it. I think the authors of the paper would agree with all of what I'm about to write. First, the background theory of evolution is not questioned. The question is not the one I had asked, whether evolution could have produced human intelligence, but how it did so; for there is no doubt that it did. No other possibility is on the table.

Second, there is a paucity of evidence to test a theory. Therefore (p. 17),

"The main weakness of the model is that the data are not available to provide simple strong or direct tests. Nevertheless, the analysis of the temporal patterns indicated by the fossil record, the specific design features of the human brain, and the life history and reproductive characteristics of humans in combination provides powerful opportunities to evaluate the model against competing hypotheses."

This is representative of several similar comments throughout the paper. Third, the general mood of the paper is tentative: it's filled throughout with "may have," "might have been," and "could possibly" sorts of statements. This is not a criticism; they have shown commendable restraint.

Fourth, the authors' intent is not to prove their hypothesis (actually a model proposed by Richard Alexander in 1990), but to show its superiority over other models taken from the same evolutionary background assumptions (see the quote already given). They show how, in paleontology and anatomy, their model provides a better fit to the data than others have. It's a step in a progressive process toward what might ultimately be found to be the true and right answer; but our lack of historical evidence means that we'll probably never be able to say, "Aha! This is it!"

That much I think the authors would agree with. Now to summarize their theory. They propose that human intelligence was selected for when hominins (humans, our predecessors, and the like) achieved such ecological dominance that their primary selective competition was with each other, and not with other organisms. Some of them, by the usual process of blind, random variation, developed cognitive skills supporting social interactions, which gave them a selective advantage compared to other hominins. Social intelligence became the big evolutionary variable. This led to an "evolutionary arms race" in which increasingly complex intellectual skills for social functioning were selected for and supported in succeeding generations. Those hominins who (by the usual process of blind, random variation, of course) were born with higher skills left more offspring behind. Eventually the whole human species acquired and shared this high intelligence. (Jordan also summarized the theory in his comments on that prior post, which I can't get to right now as I'm writing offline.)

This is not my field, yet I have questions. As far as I can tell, the authors succeed in showing this model to be better than other evolutionary theories. Still I wonder:
 
• How did humans gain that initial ecological dominance without having high intelligence first? Didn't that dominance come as a result of intelligence? It seems like the cause is also the effect here. 
• This hypothesis depends entirely on the evolutionary pull of human social intelligence. It assumes that other abstract intelligence would follow along with it. How? Why would evolution select for the ability (for example) to use complex numbers (involving the square root of -1) to compute phase and current in electrical circuits? Can they support the assumption that this sort of intelligence naturally tags along with social intelligence? How? 
• Isn't it nice to be able to take your background assumptions as accurate and unchallenged, so that all you have to do is come up with the best un-demonstrable idea within those assumptions? 
• Isn't blind, random variation wonderful?

* I'm away from regular Internet access again for several days. I can still write blog entries offline and post them when I get a connection, but some links are hard to find and insert when I do that. As for reading and responding to comments, I'll stay in touch as I can. 

Posted: Sun - August 19, 2007 at 07:08 AM           |


© 2004-2007 by Tom Gilson. Permission is granted to quote up to two paragraphs of any blog entry, provided that a link back to the original is included or (in print) the website address is provided. Please email me regarding longer quotes. All other rights reserved.

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