I’m attending this workshop conference on nonlinear dynamics at IISc right now. Being a workshop conference on a topic as broad as nonlinear dynamics, the workshop has people from various fields. There have been, in the first two days of the workshop conference, talks by people from neuroscience, quantum physics, evolutionary biology and one by an electrochemist.
The quantum physics talks were mostly, and without exception, bouncers, but I heard something at one of the biology talks that I found very interesting. It also gives me an opportunity and a reason to write about something that bugs me about what people think ‘evolution’ is.
The talk was by Somdatta Sinha from CCMB, Hyderabad, who, in explaining a (nonlinear) dynamical systems approach to modelling biological systems, and especially genotypes and phenotypes, said that her simulations show that external factors affect the phenotype. This, I thought, has interesting implications.
This, in fact, brings me to what bugs me about what people think of evolution. An organism doesn’t change its genotype because it finds that a certain genotype is better than its own, in its present environment. The environment of an organism cannot affect the genotype at all, in fact. (When this does happen, it is almost universally fatal. Think cancer). This is actually the central dogma of biology. Evolution is Darwinian, not Lamarckian.
What this means, if one were to resort to parable, is that the genotype of the giraffe didn’t change to make its neck longer because there were leaves high up in the trees. Lamarck put forth the now invalidated theory that organisms change in order to adapt to their environment. Darwin’s idea was simpler; also more brutal. It goes like this: the giraffes that survived because their necks were slightly longer reproduced that much more often than giraffes with shorter necks. The gene (or bunch of genes) that led to this slight elongation of the neck survive more often than the genes that do the opposite, and eventually, only the genes that lead to ultra long necks survive. See what I mean about Darwin’s paradigm being more brutal?
Anyway, back to the talk on nonlinear dynamics and its implications. It is easy enough to think of situations where external factors influence the phenotype. Don’t give a child enough food, and the growth will be stunted, no matter how many miles the parents can run a day. People adapt to changes in climate all the time. (I’ve done it. I know. Bangalore’s cooold, compared to Chennai.) The thing to remember, here, is that these changes are phenotypic, not genotypic. The parents may have been athletes, but the physical development does not carry into the next generation. The only way the genotype can change is by the selection of some genes over others.
What the fact that external factors influence phenotypes does is to provide what seems to me to be a basis for the process of selection. Because external factors affect the phenotype, they affect the survival of the organisms; in the sense that organisms that have a change in phenotype that a) counters the external factors, or b) uses the external factors in some way beneficial to the organism will survive to reproduce more often than organisms whose phenotype doesn’t change in response to external factors, or changes in some way that’s harmful.
The conclusion of the above argument is this, and this is to me quite interesting: there can be situations in which the ability to adapt to the environment is more valuable than any particular phenotypic strength. Genes that confer on the organism an ability to adapt to its surroundings will survive more than genes that confer some particular strength but make the organism immutable. I cannot think of a better example for this phenomenon than the case of the Homo sapien.
We cannot fly, breathe underwater, climb trees, or even run fast. Our necks aren’t long, our legs aren’t strong, and our senses of sight, smell and hearing aren’t very good. What we have in lieu of all these abilities are our brains. In about 200000 years of evolution, human beings have colonised every part of the planet, beaten every organism on its own turf, and may have already changed the planet’s atmosphere irreparably. Our abilities to adapt to our ever-changing surroundings are what make us human, and make us, arguably, the most successful species this planet has ever seen.
Conference, not workshop. It’s officially called the International Conference, Perspectives on Nonlinear Dynamics, 2010.