The older you grow, the less your family background predicts your IQ and the better your genes predict it. An orphan of brilliant parents adopted into a family of dullards might do poorly at school but by middle age could end up a brilliant professor of quantum mechanics. An orphan of dullard parents, reared in a family of Nobel Prize-winners, might do well at school but by middle age may be working in a job that requires little reading or little deep thought.
Numerically, the contribution of “shared environment” to variation in IQ in a western society is roughly 40 percent in people younger than 20. It then falls rapidly to zero in older age groups. Conversely, the contribution of genes to explaining variation in IQ rises from 20 percent in infancy to 40 percent in childhood to 60 percent in adults and maybe 80 percent in people past middle age.
The Agile Gene: How Nature Turns on Nurture
by Matt Ridley
In the follow-up to his bestseller, Genome, Matt Ridley takes on a centuries-old question: is it nature or nurture that makes us who we are? Ridley asserts that the question itself is a “false dichotomy.” Using copious examples from human and animal behavior, he presents the notion that our environment affects the way our genes express themselves.
Ridley writes that the switches controlling our 30,000 or so genes not only form the structures of our brains but do so in such a way as to cue off the outside environment in a tidy feedback loop of body and behavior. In fact, it seems clear that we have genetic “thermostats” that are turned up and down by environmental factors. He challenges both scientific and folk concepts, from assumptions of what’s malleable in a person to sociobiological theories based solely on the “selfish gene.”
Ridley’s proof is in the pudding for such touchy subjects as monogamy, aggression, and parenting, which we now understand have some genetic controls. Nevertheless, “the more we understand both our genes and our instincts, the less inevitable they seem.”
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Nature via Nurture: Genes, Experience, & What Makes Us Human
by Matt Ridley
(2003)
Prologue: Twelve Hairy Men
1. The Paragon of Animals
2. A Plethora of Instincts
3. A Convenient Jingle
4. The Madness of Causes
5. Genes in the Fourth Dimension
6. Formative Years
7. Learning Lessons
8. Conundrums of Culture
9. The Seven Meanings of ‘Gene’
10. A Budget of Paradoxical Morals
Epilogue: Homo stramineus – the Straw Man
Matt Ridley
https://kushima38.kagoyacloud.com/?p=40851