Behavioral Evolution II. 1h 37m Robert Sapolsky video.
Sapolsky starts with a nice review of the previous lecture which makes it easy to learn this subtle material. He keeps digging deeper with more examples and theory. Individual selection views behavior as an epiphenomena to get genes propagated. Kin selection and reciprocal altruism round out the basic theoretic foundation for behavioral evolution. These principles of sociobiology / evolutionary psychology "explain" human war, genocide, infanticide, etc. It seems that we can predict most of a species' behavioral characteristics just from knowing a few things about their skeletons. This lecture cites several more successful examples and then builds to some deep criticisms of sociobiology which presage the next lectures on molecular genetics.
There is a pattern to infanticide: it is almost always the males that kill babies of their own species and it tends to happen only in those species where the average interbirth interval in females is greater than the average tenure of a high-ranking male (e.g., langur & vervet monkeys, lions, and mountain gorillas). In species with infanticidal males, some females will abort their pregnancy or enter pseudo-estrus (physiological signs that she is ovulating and ready to mate) if a new high-ranking male enters the picture (so that she doesn't waste time in a pregnancy that will result in the death of her newborn). More variations are presented all corroborating the sociobiological perspective.
Low-ranking males will sometimes kidnap the children of high-ranking males that are attacking them (the message being: lay off or your kid will "get it"). We know that they understand the parental relationships involved because Sapolsky himself documented a Baboon that made a mistake by kidnapping the "wrong" kid and threw the child aside before running away.
Female fetuses tend to be less calorically demanding and are preferred in times of drought or if the mother is low-ranking (her boys would likely be low-ranking and may never father children). 53% of human fertilizations are for males. At birth it is 51% male. Not until adolescence does the male-female ratio switch. After a boy birth, the body weight of the next child tends to be less. Robert Trivers figured out the sociobiology of sex ratios as a function of social context. Whichever sex is more common is less desirable and this creates a dynamic tension in the sex ratio that hovers around equilibrium.
Polyandry is one female with several male mates. Adelphic polyandry means that the males in the "marriage" are all brothers. It happens with lions and there is a group of humans in Tibet where marginal farming land has led to this form of polyandry to prevent the subdivisioning of land which is already too poor for subsistence.
Imprinted genes are a class of genetic traits that work (controlled by methylation) differently depending on the sex of the parent they come from. David Haig developed the theory in the early 1990s. The theory builds on kin selection in the face of genomic conflict between mother and father. All of the imprinted genes from males promote fetal growth: faster metabolism, thicker uterus, production of more growth hormone. The genes from the female tends to scale back on these fetal growth effects for example by decreasing the receptiveness of the growth hormone receptor. A few imprinted genes affect the child after birth, for example the male gene might increase the suckling response. A fascinating evolutionary arms race over the genomic conflict between males and females. Another such evolutionary arms race was documented by William Rice at Santa Cruz. Some flies have multiple male partners so the female has sperm from several males. Some of these sperm produce a toxin that kills the other sperm.
Baboons have male exogamy: upon sexual maturity males leave their troop to join a group of all related females. In Chimps there is female exogamy: the males in a troup are all related and females leave their birth troop upon sexual maturity to find new group. This has evolutionary implications for behavior. With male exogamy, we find more intra-group fighting between males (and that plays out in the Baboon). With female exogamy we find more inter-group fighting (Chimps are notorious for thier "border patrols" and their inter-group fighting which can reach the point where it meets the UN defintion for genocide). Our closest animal relative!!!
Nice reminder of Marlin Perkins and that great program of my youth: "Wild Kingdom". Though Sapolsky is critical of aspects of the program. Remarkably the program is still running on Cable (though Perkins died in 1986).
After Sapolsky strongly criticized group selection ideas in the previous lectures, he now finds that in a more refined approach it is salient. David Sloan Wilson (distinguished Binghamton University biologist and long-time group selection advocate) and E.O. Wilson (founder of Sociobiology and long-time individual selection advocate) wrote some papers in 2007-8 where they burried the hatchet of their long-time disagreement and agreed to agree that group selection in at least a few particular circumstances actually makes sense. If a small group of individuals becomes isolated from the large population of a species, the smaller isolated group will due to kin selection influences develop more cooperation yielding a larger payoff (in the game theory sense) and this will fix these cooperative traits in the isolated population. Then when these "founders" are reintroduced to the larger population, their cooperative traits will outcompete the others until their group becomes prevalent. This scenario shows how kin selection can lead to reciprocal altruism and it provides a model for fixing cooperation vis-a-vis group selection to "crystalize" cooperation.
This leads to David Sloan Wilson's idea of multi-level selection: depending on the circumstances the most important thing in evolution might be a single gene, a single organism, or a single group.
Two warnings about applying all this to humans: 1) we need to beware of the temptation to take traits and behaviors in the animal world and apply them as inflated models of human behavior. 2) Then you might see rape, infanticide, kidnapping, and genocide as "natural" and inevitable. We can fall into major distortions!!! Humans have a unique evolutionary history and our quirks and complex personalities mean that such modeling can be shaky ... very shaky.
Then he starts to criticize sociobiology. E.O. Wilson said that eventually all of the social sciences will be under the wing of evolutionary biology. But sociobiology has three assuptions and each has been criticized. Sapolsky examines these.
First, there is the assumption of heritability of behavioral traits. The sociobiological accounts of the evolution of biology start sounding like "just so" stories. There is no DNA sequence specified: is it all just imaginary? When will behavioral traits have a genetic influence? In which environments will certain behaviors have a genetic influence. Sociobiology does not solve these problems.
Secondly, there is the assumption that a selected trait is adaptive. Does evolution apply the scalpel of optimization to behavior selection? Are these "just so" stories disprovable? Stephen Jay Gould and molecular geneticist Richard Lewontin introduced the idea of a spandrel: traits that have evolved not due to their adaptiveness but because they are the accidental byproduct of adaptive traits. The word spandrel is borrowed from the architecture of arches: between two arches, geometrically you will inevitably have a space that architects might as well decorate. For example, the shape of the human chin is a spandrel it results inevitably from a foreshortened muzzle and the angle of our jaw. "Evolution is not an inventor, it is a tinkerer" (Sapolsky cites Andre Lwoff but my google search did not corroborate the attribution). Evolution works with preexisting structures and does not optimize every trait.
Thirdly, there is the assuption of gradualism. Stephen Jay Gould argues that evolution is not gradual, but operates as punctuated equilibrium alternating between periods of rapid change and stasis (equilibrium). Sapolsky suggests that the molecular biology supports this view and hints that we will go in more depth in the next lectures.
In addition to these scientific criticisms of sociobiology, there are social, cultural and political criticisms. It tends to be the Western evolutionary biologists who focus on hyper competition as a scalpel for optimizing selection. The Soviet school of evolutionary biologists tend to emphasize abiotic selection with less competition. But the discussion can also get heatedly political. E.O. Wilson, Robert Trivers, and Irven DeVore, as leading sociobiologists all tended to be white males from the South. Stephen Jay Gould and other critics tended to be Marxists from the East. Once a Marxist pushed Wilson from the stage. Is it scientifically suspicious that a theory that seems to justify the dominance of men happened to be promoted by men from the South? And the theory that would be most amenable to Marxists with their interest in revolution might promote a theory that sees evolution highlighted by periods of rapid change?
Is rape a valid competitive strategy or a psychopathology? Is the fact that children are more likely to be killed by stepfathers rather than their natural parents the result of the natural biology of gene competition or is it due to socioeconomic factors? The impression that sociobiology justifies a world in which male domination in a stratified and aggressive world where competition pays off has plagued the field since its founding.
2. Behavioral Evolution