Evelyn Fox Keller, Professor of History and Philosophy of Science at MIT, comes at the old nature versus nurture question from an interesting direction. What do you mean, she asks, by versus.
"What do you mean" is literal. Keller probes at language and meaning in the book.
The story starts with Francis Galton. Galton was Charles Darwin's half cousin. He wrote a book called English Men of Science: Their Nature and Nurture. The theme of the book was: how could Francis Galton be so smart?
From his very comfortable and long-inherited family home, Galton set down an answer: nature. Francis Galton was smart by nature. He had inherited it. And because of this, he proposed, the English people should give to people like Francis Galton, money to breed.
See? Francis Galton was smart. As a writer, he could overlay complexly interesting double meanings, on simple common words. "Nurture," about English Men of Science, is overloaded. As is the question of their nature.
Drums and Drummers
For explaining what she means by mirage, about a space between nature and nurture, Keller picks up Hans Kummer's analogy of drummers and drums. It would be meaningless to ask, how much of the sound comes from the drummer, and how much comes from the drum.
A study shows that the heritability of a trait difference in the mating behavior of fruits flies is, say, 50.00%. Then, one fruit fly is cloned, and the experiment is repeated. The heritability of the very same trait difference would now be zero.
Little h and Big H Heritability
There are two measure of heritability. The book lays them out, if you want to get into it..
Agricultural breeding science focuses on little h, or narrow heritability. It is the easier to measure. They don't care, about any one corn plant in the field.
Behavioral genetics (including of people) uses Big H or broad heritability. It is the harder to measure. And you can't do experiments on people the way you can on corn. Double trouble.
There is a third understanding of heritability, which is a nontechnical one. We want to know how much of our own eye color we got from mom, or from grandma. This meaning is a mirage. It is the drum and drummer question. It can't be asked of individuals, but only of populations. And it can't be asked of traits, but only of trait differences.
Omit Needless Words!
A review in the American Scientist calls Keller's book the Strunk and White of heritability.
if there were a little manifesto that we could curl up with and reread every couple of years to restore to our thinking the clarity we know this difficult subject deserves? The Mirage of a Space Between Nature and Nurture, by Evelyn Fox Keller, may be just the book we’ve been waiting for.
Science reporters dealing with the latest result of a twin study, say, could benefit from having the book on their desk. As could we. As could, actually, scientists in the field. Keller shows scientists who have a solid grasp on the concepts, repeatedly slipping in what they say.
This little book has four main takeaway points: Discussion of the issues is muddled in history and language; the move from individuals to populations; the move from traits to trait differences; and the contributions of modern genetics. One hundred well written pages, with one chapter for each.
Evelyn Fox Keller, The Mirage of a Space Between Nature and Nurture. Duke University Press, 2010.