Beware the adaptationist paradigm

The theory of evolution is one of my favourite things in the world. When scientists talk of an “elegant” theory, this is what they mean. People who deny evolution on religious ground without understanding it make me cross.

Evolution is not a belief, evolution is.

Part of the problem is that too many people don’t understand evolution – it doesn’t happen by chance, although variation, which itself is partly random, is a central part of how evolution works.

However, it is too easy to view everything as an evolved adaptation as Stephen Jay Gould and Richard Lewontin wrote in their seminal 1979 paper “The Spandrels of San Marco” (http://ethomas.web.wesleyan.edu/wescourses/2004s/ees227/01/spandrels.html).

They called for a pluralistic view of evolutionary biology rather than for organisms to be broken down in constituents parts, like a box full of lego that was once a pirate ship. Although they were writing 27 years ago, I think their comments still have relevance. It may be easy to come up with an adaptive hypothesis without fully considering the alternatives.

They wrote that not every body part, for instance, has arisen for an adaptive reason, partly because the body evolved not discretely but as a whole, but this doesn’t mean that the particular body part has no role. In the sphere of architecture they point out that in St Mark’s cathedral in Venice one might assume that the richly decorated “spandrels” below the dome were designed as upside-down triangles on purpose. The fact is, they are actually holding up the dome! (http://en.wikipedia.org/wiki/Spandrel)

“One must not confuse the fact that a structure is used in some way … with the primary evolutionary reason for its existence and conformation.”

Further, using adaptations as an explanation appeals to the human mind, because we like stories. But telling stories is not scientific and a new explanation can always be invented if an old one turns out to be unsatisifcatory. “Since the range of adaptive stories is as wide as our minds are fertile, new stories can always be postulated.”

“Often, evolutionists use consistency with natural selection as the sole criterion and consider their work done when they concoct a plausible story... The key to historical research lies in devising criteria to identify proper explanations among the substantial set of plausible pathways to any modern result.” They called for a more holistic approach which “could put organisms, with all their recalcitrant yet intelligible complexity, back into evolutionary theory”.

Living language

“Do you want to demonstrate that the living also have a wordless language, with which books cannot be written but which can only be lived, second by second, which cannot be recorded or remembered? First comes this wordless language of living bodies … then the words books are written with, and attempts to translate that first language are vain…”

From “If on a Winter’s Night a Traveler” by Italo Calvino