VARIATION
‘Variability,’ wrote Darwin in On the Origin of Species, arises ‘from the indirect and direct action of the external conditions of life, and from use and disuse.’
Just as his long shot on our African origins had to wait a century for confirmation, so Darwin’s long-range punt on what causes variation is only now starting to look very near the mark. Until quite recently it was believed that variation came solely from copying errors during cell division. Copying errors were never very convincing as a sufficient cause for natural selection. Awareness of this vulnerability led neo-Darwinists to aggressively patrol this weak point. Doubts about the dogma of random genetic mutation were met not with defence but attack. Skeptics were accused of being too lily-livered to endure a random universe. Only the proud neo-Darwinist, he alone, was able to breathe the thin air of negative capability, to look around at a random universe and call it home.
Behind the aggressive patrols lurked a guilty knowledge of how abruptly they had split from Darwin. This guilt the neo-Darwinists dealt with by deploying what EP Thompson once called (in another context) ‘the massive condescension of posterity.’
Poor old Charles Darwin, they’d lament, if only he had known about Mendelian genetics then he wouldn’t have stumbled about in the dark banging his head on antiquated beams, thinking that development and environment are somehow factors in evolution. If only the dear, sweet, kind but tragically misguided bald old bastard had lived to see August Weissmann prove discrete genes to be immortal.
The neo-Darwinist pictures himself floating in a spacesuit behind the Down House bookshelves, like Matthew McConaughey in Interstellar, shouting ‘DNA,’ as poor benighted Darwin bimbles about with specimens of barnacles.
‘The idea that all DNA changes arise through random mistakes is wrong,’ claim Eva Jablonka and Marion Lamb. Environmental stress has been shown to give rise to mutations. Mutation is often, therefore, far from random.59 The recognition that mutation is a response to external events is part of the intrusion of the outside world into the playpen of Genes R Us evolutionary theory.
But even though epigenetics has now shown how heritable traits can be transmitted without altering DNA sequence at all, I for one refuse to be as condescending to neo-Darwinists as they’ve been to everybody else. After all, their elementary conceptual blunder was based on lack of evidence. Some things were not known way back when they formed their primitive beliefs about discrete germline cells. The poor fools simply didn’t know how methyltransferase enzymes at CpG sites silence genes. But they were so sweeeeet with their adorable conferences on Random Genetic Mutation, and all their liddle-widdle powerpoint graphs with those cutesie-wootsie lines, emanating from gene to every single living thing in the whole world ever, like the rays of the sun, while innocent the whole time of how S-adenosyl-l-methionine’s electrophilic attack activates the C(5) atom. Bless!
Eva Jablonka and Marion Lamb, Evolution in Four Dimensions, MIT Press (2014). |