Adelaide is an unusual city, a mix of parochialism and conservatism and progressive, innovative thinking. One of the examples of the latter is the Thinkers in Residence program, where world renowned thinkers are invited to Adelaide to discuss issues relevant to urban and regional development. Currently, the Thinker in Residence is Baroness Susan Greenfield, a world authority on neuroscience cognition the pharmacology of Alzheimer’s disease. Baroness Greenfield is considered to be the 14th most inspirational woman in the owrld (and as she wryly notes, Dolly Parton is the 9th). Last Friday night I went to a symposium on “Neurotransmitters in the Brain”, where I listened to here give a talk entitled “Is there more to the brain then neurotransmitters?”.
What has this got to do with evolutionary biology?
Well, Paleyists keep on going on the imminent collapse of “Darwinism”, but they have probably not been talking much to working biologists. Neuroscientists are a fairly down to earth group of people, hardly the image of “Dogmatic Darwinists” that the Paleyists promote, yet evolutionary biology and evolutionary insights were woven into all the talks. Theodosius Dobzhansky once said “In biology nothing makes sense except in the light of evolution”, and this is nowhere as true as for neuroscience.
Baroness Greenfield’s talk was a tour de force, an inspiring, sparking rush of ideas. Even I, who tries to keep up with the more advanced literature, as amazed by the images of linked nerve cells growing on computer chips, prototypes of advanced brain implants. I am now a confirmed Geenfield Groupie.
One of the elements of her talk was about the enzyme acetylcholinesterase. Some of you might recognize this enzyme, as it breaks down acetylcholine, the neurotransmitter of the parasympathetic and skeletal muscular system, and is responsible for terminating the effect of a nerve impulse. It turns out that acetylcholinesterase also is a neuronal growth factor, an effect that is unrelated to its enzyme activity. It is turning out that many proteins can play multiple important roles that are unrelated to their originally described “primary” enzymic activity. Why is this important? One of the Paleyist’s claims is that complex systems cannot be built because intermediate systems have no evolutionary advantage, a eubacterial flagella without a motor has no useful function and a motor on its own has no function, therefore it cannot evolve via natural selection. But many proteins have multiple useful functions, and can be doing things other than the thing we think of as the “primary function”. Indeed, the very concept of a “primary function” may simply be an artifact of the way we discover proteins. The eubacterial flagella is an effective secretion system, and the motor is a member of a class of proteins that help power secretion. It is easy to see how these systems could have evolutionarily important functions on their own, and be co-opted into a motility role. Co-option is extensive in biological systems, as the Paleyists would know if they talked extensively with working biologists, and there is no barrier to building complex systems as these can play multiple, important roles at various stages in their assembly.
After the talk, I wandered off amazed and enthralled by all the ideas I had just heard. In a bit of a daze, I got in a lift, to discover that I was sharing the lift with Baroness Greenfield and one other person. Here I was in close proximity to the person whose luminous ideas had enchanted me, here was my opportunity to say something meaningful and profound. What did I say? “That was a very nice talk, thank you”.