George Williams is dead. He was one of a group of biologists who completely changed the nature of evolutionary theory in the past half century. Englishmen William Hamilton and John Maynard Smith. Americans George Williams, Robert Trivers, and Edward O. Wilson. Working in a somewhat different way and very much more publicly, but still very important, were Richard Dawkins on one side of the Atlantic and Stephen Jay Gould on the other. It was by anyone’s assessment an incredibly exciting time and it continues today with a new generation. I think for example of the work of the evolutionary developmental biologist Sean Carroll, not to mention the wonderful work in the human realm, both with fossil discoveries (think Don Johanson and Lucy) and the findings and implications of the Human Genome Project (think Francis Collins).
The major issue, still one much debated, was about the nature of the key evolutionary mechanism of natural selection. The co-discoverers of natural selection—Charles Darwin and Alfred Russel Wallace—had differed on this. Darwin always thought that natural selection works on the individual and only indirectly on the group. It is organism against organism, either in the same species or between members of different species or with the environment. Wallace, to the contrary, thought that selection could work for the good of the group even against the interests of the individual. One thing they argued about was the sterility of hybrids like the mule. Darwin could never see why it was in the interests of the parents that their offspring be sterile. Wallace thought it was in the interests of the groups, not wanting hybrids that were (literally) neither fish nor fowl, to have the offspring sterile.
Without modern genetics, no definitive answers could be given. But Darwin did tackle in prescient ways major problems. What about social insects where sterile workers have no offspring themselves but work lifelong for the good of the nest? He argued that in such cases we have a kind of family selection, where either you think of the nest as a kind of single superorganism or you think in terms of relatives. Overall perhaps you have a single organism, but animal breeders show that you can breed for qualities in (sterile) bullocks by going back to the parent stock. So selection can show how the caste members of social insect societies can be different and adapted to their various roles.
Humans were a major problem. Wallace opted out of the whole equation, arguing that spirit forces mold our evolution and subsequent nature. Darwin stuck to his guns and even when it came to morality, despite a somewhat misleading formulation, argued that if the individual doesn’t benefit from helping others, then morality is just not on. He himself suggested that morality might evolve as a result of “you scratch my back and I’ll scratch yours”—moral people get help when they need it and immoral people don’t. Today, this in the trade is known as “reciprocal altruism.” He also thought that language and so forth binds human societies so tightly that we can function like social insects—we work together like the ants and the wasps, in our case using morality rather than just unthinking instinct.
After Darwin and Wallace, natural selection itself was not much regarded for many years. People became evolutionists but sought other mechanisms. It was not until the 1930s that biologists realized that Darwinian selection and Mendelian genetics complement each other and that through their union one builds a functioning theory – known as neo-Darwinism in Britain and the synthetic theory in the USA. But no one much bothered about the unit of selection and indeed most casually assumed that groups could be favored as well as and at times over individuals. Typical was the ethologist Konrad Lorenz in his book on aggression where—discussing why a defeated male dog falls on its back thus exposing its genitals to the winning dog—he explains that a drop of urine appears and that this turns off the winner’s aggression. Selection has brought this on “for the good of the species.” The defeated dog may later be able to help the species even though the winner still has him as a potential rival.
The group I noted above, George Williams above all, would have none of this. They were with Darwin. Natural selection favors the individual and never (or only in very peculiar circumstances) the group. Williams’s Adaptation and Natural Selection, published in 1966, was a model of elegance, explaining lucidly why this must be so. Group selection, as it became known, is too open to cheating. Suppose you have a group of organisms and that they are all helping each other (in the lingo, they are altruists). Now suppose mutation brings on a selfish group member. It is going to benefit two ways, both from the help of others and from not wasting its own resources on others. So it will be at a selective advantage and its type will spread through the group. It was not that Williams and others were neo-Social Darwinians, thinking that nature is red in tooth and claw and a jolly good thing too. It was that group selection simply doesn’t work.
And what an energizing discovery that was too! Hordes of the best graduate students took the ideas and ran with them. There was some terrific work done on sex ratios. By and large, male animals are a bit of a waste. It is the females that do all of the child rearing. If sex is a good thing (and there has been a lot of discussion about that) then probably you could get by with just a few males for breeding purposes and generally go female. Say 10% male and the rest female.
But in fact, we generally find that the ratio of male to female is 50:50. Why? From a group perspective this makes no sense. From an individual perspective, it follows easily. Parents of males with only a 10-percent ratio are doing biologically better (spreading more of their genes) than parents of females with a 90-percent ratio. So (assuming that genetics is behind propensities to produce kids of one sex rather than another) they are favored by selection and will increase in numbers until parity is reached. What is lovely is that there are expected exceptions. If for instance your sons compete for the same females, biologically you are wasting your resources because any son would do and only one can succeed. Better to have fewer sons and more daughters. (This is known as “local mate competition.”) There is some wonderful work on this on fig wasps in Panama. The males emerge first and gather around waiting for females to emerge. Since often males are from the same mother, you expect distorted sex ratios and you find them. (Whoever said that you cannot make predictions about evolution?!)
George Williams, a rather quiet man but a wonderful friend, was one of the pioneers in this kind of thinking. Today, evolutionists all over the world will be shedding a tear at his memory, and raising a glass in his honor.