From Nova’s Becoming Human, Part 1 at -9:00 (Nova uses a countdown timer). Discussing the hypothesis that short-term (hundreds to thousands of years) extreme climate variability drove human evolution, and particularly increases in brain size, in the ramp-up from 400 cc or so to Homo habilis’s 600 or 700 cc, and maybe on to larger brained successors, the film says:
Narrator: “This observation led [Rick Potts] to an amazing new idea: Rapid [climate] change as a catalyst for our evolution.”
Rick Potts: “And I began to think that well maybe it’s not the particular environment of a savanna that was important, but the tendency of the environment to change.”
[Here it is]
Narrator: “Could it be that the need to survive violent swings of climate made our ancestors more adaptable?”
Right. And it was the need of giraffes to reach higher branches with yummier leaves that made them grow longer f***ing necks. Gaaaaah!!! Lamarck is dead! And so is Bergson.
That locution, that phraseology, that notion that a “need” somehow drives evolution, drives me bats. “Needs” don’t make populations evolve anything. Now, properties of an environment may select for traits in a population if appropriate variants occur, and as a result of that selective process the population may be more adapted to that selective environment. And it’s not necessarily implausible that an environment that varies irregularly on an appropriate time grain (bunches of generations) could select for some sort of generalized adaptability on the part of a population provided there’s some genetic basis for that adaptability that gives individuals a reproductive advantage, but a “need” doesn’t “make” the trait evolve. If that were the case we’d have wings and gills.