Monday, 25 February 2013

Relationship between intelligence and life history speed: population and individual levels

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The relationship between population and speed of life history is probably somewhat complex; but (as far as I understand the matter) I think it could be summarized by saying that:

1. At the population level, there is usually a correlation between higher intelligence and slower life history speed.

(This is presumably due to natural selection, historically, in situations where both higher intelligence and slower life history are, on average, adaptive.).

But:

2. At the individual level, within a population, intelligence and life history speed are uncorrelated.

Or, more accurately, intelligence and life history speed are dissociated at the individual level; such that a highly intelligent person may have either slower or faster life history; and the same applies to low intelligence persons.

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The dissociation can be seen in two stereotypical male high intelligence types: the sexually aggressive business executive or politician (fast life history - urgency of reproductive effort leading to early sex, multiple partners, more children with lower/ zero investment per offspring); versus the nerdy professor (slow life history - delayed reproductive effort, late marriage to single partner, few children with high investment per offspring).

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The dissociation is, presumably, caused because while intelligence and personality are inherited, life history is triggered by the environment, by some experience (probably) early in life.

Or, an individual's specific life history trajectory is selected-from a certain range of possible life history speeds.

The range of possible life history speeds is innate and inherited, but the specific life history speed which is embarked upon is a consequence of environmental cues, triggers or stimuli.

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This implies that fast life history parents often have slow life history children and vice versa.

And this means that life history is different from intelligence and personality, because childrens' intelligence and personality is, on average, similar to their parents'.

(Yet, at the same time, some populations will have different average life history speeds from others; and a different average range of life history speeds.)