There's nobody here but us chickens.

Wednesday, June 28, 2006

To revisit old thoughts with a different head...

I stumbled across an old review of the book - DC Dennett's Darwin's Dangerous Idea - that shaped my college love affair with natural selection, and it does a damn good job of shaking some of Dennett's grand edifices.
Dennett has long championed the notion that Darwinism might explain why some ideas and styles flourish while others perish.6 Darwinism thus explains not just the biological origin of consciousness and culture, but their changing contents.... why is he ineluctably drawn to the view that cultural change involves some brand of Darwinism? The reason is that he believes natural selection is an "algorithmic process," a blind, formal procedure whose operation is guaranteed to return a certain kind of result. A defining property of an algorithmic process is its "substrate neutrality": An algorithm does a job and returns a result whatever the input. Dennett concludes that natural selection, as an algorithm, is also substrate neutral. One can select between genes on chromosomes, codes in a computer, or ideas in a culture. As long as mutation, replication, and differential survival occur, any substrate can be selected. For instance, ideas can change (mutate), they can spread (replicate), and some can die out while others persist (differential survival), so we would seem to have a substrate suited for selection. Following Dawkins, Dennett claims that the substrate that gets selected in cultural evolution is the "meme," any memorable idea, jingle, or fashion that lasts long enough to get copied by another person.

This substrate neutrality argument is supremely important to Dennett. It -- and nothing else -- explains why selection can be lifted from its historical base in biology. It is what makes Darwinism so dangerous. But Dennett slips here. While it is true that many different kinds of substrate can be selected, it is simply not true that Darwinism works with any substrate, no matter what. Indeed Darwinism can't even explain old-fashioned biological evolution if the hereditary substrate doesn't behave just right. Evolution would quickly grind to a halt, for instance, if inheritance were blending, not particulate. With blending inheritance, the genetic material from two parents seamlessly blends together like different colored paints. With particulate Mendelian inheritance, genes from Mom and Dad remain forever distinct in Junior. This substrate problem was so acute that turn-of-the-century biologists -- all fans of blending inheritance -- concluded that Darwinism just can't work. Modern evolutionary genetics was born in 1930 when Sir Ronald Fisher cracked this problem: Population genetics shows that particulate Mendelian inheritance saves the day. It is just the kind of substrate needed for evolution by natural selection to work.

What, then, about Dennett's memes -- all those "tunes, ideas, catch-phrases, clothes-fashions, ways of making pots or of building arches." Do they show particulate or blending inheritance? Do street fashion and high fashion segregate like good genes, or do they first mix before replicating in magazines or storefronts? Does postmodern architecture reflect a blending of the modernist and classical or the inheritance of distinct LeCorbusier and Vitruvius genes? I do not know the answers to these questions. And neither does Dennett. And neither does anyone else.
The whole review is here.