Blute Blog

I was saddened to read in the New York Times recently of the death of Fran de Waal of Emory University and the Yerkes Primate Research Centre at age 75. I have not read all of his more recent books nor would I probably agree with all of his reflections on animal cognition, especially his apparent recent skepticism about science. However, I certainly remember being impressed by his early experimental proof that chimps can learn socially by observation. He and some colleagues created a puzzle that was too difficult for members of two groups to solve. But then they took an individual from each group and trained them separately to solve it with individual learning methods, but differently. When they put the two back in the separate groups, the members of each group learned to do so – definitely by observation because each group learned the specific method of the model placed in their group.

I was so impressed that when decades ago I was in charge briefly of a dinner with a guest speaker held annually at my University of Toronto campus, I invited de Waal to speak and enjoyed his visit immensely.

Now I see in Nature on March 21 of this year that Bridges et. al. have performed a similar experiment successfully on, guess what, bumblebees!

In 2016 I published an article on “density-dependent selection revisited: mechanisms linking explanantia and explananda” in Biological Theory. Levels of selection was discussed there briefly, but only to argue that when a new level is added, the old does not disappear but becomes part of the mechanism of development of the new. The point I would like to make here is the more general one that density-dependence is an ecological theory which can be applied to multilevel selection which makes it unlike any others that I am aware of.

To summarize briefly, the theory was that (assuming somatic and reproductive functions utilize the same resource and that they interact cooperatively) low density relative to resources i.e. plentiful resources favour consumption (eating and excreting) and producing many small offspring. High density relative to resources (i.e. scarce resources), on the other hand, favour digestion (breaking down and building up for maintenance, motility and mutability – the 3 M’s) and re-producing (producing a few large offspring capable of giving rise to grand-offspring). The reason for these is that the small and/or those with short, fast life cycles (the r selected) have a disproportionate surface area relative to volume while the large and/or those with long, slow life cycles (the K selected) have a disproportionate volume relative to surface area. The former is good for consuming and producing while the latter is good for digesting and re-producing. What does that mean for multi-level selection? Obviously in retrospect, it means that plentiful resources favour lower levels (individuals within groups) and scarce resources favour higher levels (groups themselves).

Viewed from the ecological perspective of density-dependent selection then, it is no wonder that members of flocks of birds, schools of fish, herds of deer etc. commonly hang out together waiting for tough times to improve, or migrate together, or sometimes innovate together – the 3M’s. Indeed, if density relative to resources and those relative to antagonists both matter and are positively correlated in time and space, it should not be surprising to see, as we do, that such flocks, schools, herds etc. repeatedly migrate together between good feeding and good breeding grounds.

On the other hand, major transitions in evolution such as a transitions from unicellular to multicellular organisms are cases in which this approach to multilevel selection may be difficult to justify. If we assume that new more inclusive entities have an outer membrane, the consumption (eating and excreting) of the small would have to take place at some cost to the large, and the digestion (breaking down and building up) of the large would have to take place at some cost to the small – all of which would make them different situations from cases in which the two are separate. However that may not be a fatal flaw – after all, for the low density case, some cells do die during multicellular development without the whole doing so and for the high density case, some large and/or long-lived multicellular organisms do under go senescence without becoming extinct.

At a conference, I was recently asked why in my paper on a theory of sexual selection, I proposed that conventional sex between males and females is trade in which males include females as well as males among their offspring and females include males as well as females among their offspring. Of course the reason given was the proposal that there are some naturally-selected differences between them, and that under uncertainty, such trade reduces the risk of extinction like investing in an index fund rather than trying to pick stocks or dollar cost averaging rather than trying to time markets. However, the point of the query was why specify the function as trading the sex of some offspring rather than just creating (explicitly or implicitly genetic) variation which is the most common explanation.

The reason was that there are so many genetic (and environmental) mechanisms of sex determination, many more than the familiar XY and ZW systems, many of which remain unknown, even mysterious. My way for simplicity’s sake was to take what is known as “the phenotypic gambit”. If one is willing to assume that the often many genes involved in influencing a trait have an additive effect on fitness, then that effect will be heritable and hence available for natural selection to work on. Under those conditions then, one can speak of the evolution of observable characteristics such as those of males and females and not just of genes.

Michael Ruse, the distinguished philosopher of Biology kindly sent me a copy of his new book, Why We Hate: Understanding the Roots of Human Conflict after I congratulated him on his receipt of ISHPSSB’s David L. Hull prize. We were old acquaintances from his time at the University of Guelph in Ontario before he left for Florida State University. In his new book he mostly links why we hate to the coming of agriculture which mostly makes sense to me. On the other hand, I can imagine when some foraging groups travelled through a familiar landscape on a route timed to when and where particular resources were expected to become available, that they might have encountered each other at a point utilized by two groups and came into conflict, even violence there. I suppose we will never know.

Meanwhile, that is not the point of this post. I also went back and reread his 2017 book Simply Darwin in a Great Lives series which was on my shelf and it reminded me of something that I knew but had forgotten. Beginning roughly in the last quarter of the 20the century, there has been an explosion of work in almost all of the social sciences arguing that culture changes by processes essentially analogous to those of biological evolution. Ruse’s book reminded me that Darwin used the concept of artificial selection to explain to readers (and perhaps to himself) the concept of natural selection. But what exerts artificial selection except the beliefs and values i.e. the culture of human groups small and large – preferences for large plants and animals in farming and animal husbandry for example. So the question arises, was the origin of the analogy between the two forms of evolution the cultural to the biological rather than the biological to the cultural in the first place?

I know where mine went. I spent most of it refereeing a very long book with articles by many authors. Interesting but . . . Oh well, fall is here and I a getting back to my own work so stay tuned.