Bicoid, nanos, and bricolage

flagellum cartoon

Intelligent Design creationists are extremely fond of diagrams like those on the right. Textbook illustrators like them because they simplify and make the general organization of the components clear—reducing proteins to smooth ovoids removes distractions from the main points—but creationists like them for the wrong reasons. "Look at that—it's engineered! It's as if God uses a CAD program to design complex biological systems!" They like the implication that everything is done with laser-guided precision, and most importantly, that every piece was designed with intent, to fill a specific role in an apparatus that looks like it came out of a high-tech machine shop at a Boeing aerospace lab.

This is, of course, misleading. Real organelles in biology don't look glossy and slick and mechanical; they look, well, organic, with fuzziness and variability and, most importantly, mistakes and slop. What these biological machines look like is not the precisely engineered output of a modern machine shop, but like bricolage. Bricolage is a term François Jacob used to contrast real biology with the false impression of nature as an engineer. It's an art term, referring to constructions made with whatever is at hand, a pastiche of whatever is just good enough or close enough to the desired result to make do. It covers everything from the sculptures of Alexander Calder to those ticky-tacky souvenirs made from odd bits of driftwood and shells glued together that you can find at seashore gift shops.

The closer we look at the developmental biology of organisms, the more apparent the impromptu, make-do nature of their construction is. This is not to imply that they don't work well or efficiently, but only that the signature of intent is missing. What we see is function cobbled together out of scrap from the junkyard. One clear example of this property is a gene, nanos, in Drosophila.

Continue reading "Bicoid, nanos, and bricolage" (on Pharyngula)

(Note: Pharyngula will be inaccessible for much of the day on Sunday, 13 June, while maintenance work is done on the electrical system out here in Morris, Minnesota. Look for it to be back online in the early evening.)