Richard Lewontin—Genetic Determination and Adaptation: Two Bad Metaphors

It was a fine evening here in Chicago, with all these superstars of evolutionary biology in attendance. It was also an information-dense evening — I tried to keep up on my little laptop, but I know I missed a lot. Fortunately, I’m not alone: Rob Mitchum and Jeremy Manier were also covering the event, and have a play-by-play available. I’ll just dump what I’ve got here tonight. I do have wi-fi passwords so I can get things up a little more promptly tomorrow and Saturday.

Richard Lewontin opened up with a few deprecatory comments about the religiosity of our surroundings (the talks were given in a chapel) and our purpose, the reverence given to Saint Darwin. He was there to talk about the importance and danger of metaphors, and addressed two of them. The New Testament metaphor of genes make organisms, and the Old Testament metaphor that organisms adapt to the environment.

It’s not true that genes make organisms. Organisms are consequence of interactions between inside and outside, genes and molecules, and the phenotype is not predictable from the genotype. He discussed the classic example of norms of reaction in Achillea, showing growth of clones in different environments. Cloned plants taken from cuttings — so they’re genetically identical — and grown in different environments show different patterns of growth, and, for instance, don’t show a simple relationship between morphology and the elevation at which they’re grown. Another example is bristle number in Drosophila which show similar unpredictable pattern of response to temperature. Another thing to think about: look at the fingerprints on your left and right index fingers. They’re not identical, but they have the same genes and formed in the same environment at the same time. Living organisms are the outcome of developmental and physiological processes influenced four factors: genes, non-genic molecules in the embryo, environment, and random variation.
Biologists have known this for years but have fallen prey to the metaphor of genetic determinism. (He also mentioned another bad metaphor as an aside: the cell as a machine.)

The other bad bad metaphor is the idea that organisms adapt to ecological niches. Organisms do not fit into preexisting niches. You can’t look at “niches” in the environment…there are an infinity of them. The organism determines the niche. A better idea is the concept of niche construction, in which niches change as organisms evolve. Organisms take whats available and integrate it with their biology, and the life activities of organisms determine what is relevant. When did living in water become the niche of the ancestral seal?

Organisms seek out appropriate environments, the idea of microclimate. Put mesic (adapted to environments with a moderate amount of moisture) and xeric (dry or desert) flies in evironments with different zones of humidity, one surprising result is that the xeric flies move most quickly and determinedly to moist areas, more so than mesic flies. It’s not that dry-adapted flies can handle dryness better…it’s that they’re better at finding damp microenvironments.

Lewontin gave several other examples of organisms that respond in sophisticated ways to confound simple interpretations of adaptation: that we all produce shells of altered microenvironments around us by our metabolic activity; that trees can count the number of days of a certain temperature to trigger flowering; that Daphnia measure the rate of environmental change to determine whether to reproduce sexually or asexually; that organisms modulate the statistical properties of their environment by storage.

He suggested that we need to set aside the bad metaphor of adaptation for a less bad metaphor of construction. Unfortunately, this creates a difficult situation for scientists interested in selection, because, for instance, frequency dependent selection means that the addition of new genotypes to the gene pool (which happens constantly) causes fitness to change in unpredictable ways. It’s a game of rock-paper-scissors with a lot more than just three possibilities. He closed by saying that addressing this kind of problem should be the goal of the next generation of evolutionary biologists.