So far in this course we have dealt entirely with the evolution of characters that are controlled by simple Mendelian inheritance at a single locus. There are notes on the course website about gametic disequilibrium and how allele frequencies change at two loci simultaneously, but we didn’t discuss them. In every example we’ve considered we’ve imagined that we could understand something about evolution by examining the evolution of a single gene. That’s the domain of classical population genetics. For the next few weeks we’re going to be exploring a field that’s actually older than classical population genetics, although the approach we’ll be taking to it involves the use of population genetic machinery. If you know a little about the history of evolutionary biology, you may know that after the rediscovery of Mendel’s work in 1900 there was a heated debate between the “biometricians” (e.g., Galton and Pearson) and the “Mendelians” (e.g., de Vries, Correns, Bateson, and Morgan). Biometricians asserted that the really important variation in evolution didn’t follow Mendelian rules. Height, weight, skin color, and similar traits seemed to

Human biochemical genetics

Human cooperation is an evolutionary puzzle. Unlike other creatures, people frequently cooperate with genetically unrelated strangers, often in large groups, with people they will never meet again, and when reputation gains are small or absent. These patterns of cooperation cannot be explained by the nepotistic motives associated with the evolutionary theory of kin selection and the selfish motives associated with signalling theory or the theory of reciprocal altruism. Here we show experimentally that the altruistic punishment of defectors is a key motive for the explanation of cooperation. Altruistic punishment means that individuals punish, although the punishment is costly for them and yields no material gain. We show that cooperation flourishes if altruistic punishment is possible, and breaks down if it is ruled out. The evidence indicates that negative emotions towards defectors are the proximate mechanism behind altruistic punishment. These results suggest that future study of the evolution of human cooperation should include a strong focus on explaining altruistic punishment.

/pdf/altruistic-punishment-in-humans-4yytzjzmsy.pdf

Altruistic punishment in humans.

Human cooperation is an evolutionary puzzle. Unlike other creatures, people frequently cooperate with genetically unrelated strangers, often in large groups, with people they will never meet again, and when reputation gains are small or absent. These patterns of cooperation cannot be explained by the nepotistic motives associated with the evolutionary theory of kin selection and the sel®sh motives associated with signalling theory or the theory of reciprocal altruism. Here we show experimentally that the altruistic punishment of defectors is a key motive for the explanation of cooperation. Altruistic punishment means that individuals punish, although the punishment is costly for them and yields no material gain. We show that cooperation ¯ourishes if altruistic punishment is possible, and breaks down if it is ruled out. The evidence indicates that negative emotions towards defectors are the proximate mechanism behind altruistic punishment. These results suggest that future study of the evolution of human cooperation should include a strong focus on explaining altruistic punishment.

Altruistic Punishment in Humans

I. the origin of species by means of natural selection

A DNA test to sex most birds.

http://www.tau.ac.il/~lotem/pdf/Anim95.pdf

Constraints on egg discrimination and cuckoo-host co-evolution

Rejection of cuckoo eggs in relation to host age: a possible evolutionary equilibrium

THE picture of a tiny passerine host feeding a huge cuckoo nestling challenges evolutionary biologists who explain animal behaviour as adaptive1–4. Cuckoo eggs sometimes resemble the eggs of the host, but nestlings of the common cuckoo, Cuculus canorus, look very different from the young of the host. The inability of the host to discriminate against such divergent nestlings is especially puzzling as some cuckoo hosts show a finely tuned discrimination ability between eggs5–8. Here I present a simple model to explain this paradox. The model shows that although learning to recognize eggs is adaptive, learning to recognize nestlings might not be. The mechanism of learned recognition, previously shown to maintain egg recognition, is unlikely to be adaptive for hosts like those of the common cuckoo, in which only the parasitic nestling remains in the nest. The reason that discrimination against parasite nest-lings is not adaptive is that the cost of misimprinting (learning to recognize the parasite nestling as the parents' own) exceeds the benefit of correct learning. The model also explains why nestling discrimination is mostly found in host–parasite systems in which the parasite and the hosts' young are reared together1.

Learning to recognize nestlings is maladaptive for cuckoo Cuculus canorus hosts

Nowak and Sigmund1 conclude that cooperation may have evolved through indirect reciprocity by image scoring. Their simulations1 and analytical models1,2 predict long-term cyclical dynamics between cooperative and defector populations rather than an evolutionarily stable equilibrium. Here we add a realistic feature to their model: that there are always some individuals unable to cooperate owing to their poor phenotypic condition (we call these individuals ‘phenotypic defectors’). The presence of phenotypic defectors paradoxically allows persistent discriminating cooperation under a much wider range of conditions than found by Nowak and Sigmund because there is selection against both defection and unconditional altruism. In real populations there will nearly always be some level of defection because phenotypic defectors (such as the young, sick or handicapped) may be unable to help even if they have a genetic predisposition to do so.

Evolution of cooperation between individuals

The offspring of birds and mammals solicit food from their parents by a combination of movements and vocalizations that have come to be known collectively as ‘begging’. Recently, begging has most often been viewed as an honest signal of offspring need. Yet, if offspring learn to adjust their begging efforts to the level that rewards them most, begging intensities may also reflect offsprings9 past experience rather than their precise current needs. Here we show that bird nestlings with equal levels of need can learn to beg at remarkably different levels. These experiments with hand–raised house sparrows ( Passer domesticus ) indicated that chicks learn to modify begging levels within a few hours. Moreover, we found that the begging postures of hungry chicks in natural nests are correlated with the average postures that had previously yielded them parental feedings. Such learning challenges parental ability to assess offspring needs and may require that, in response, parents somehow filter out learned differences in offspring signals.

/pdf/experimental-evidence-for-offspring-learning-in-parent-3xi2hbv6b7.pdf

Arnon Lotem

Papers

Constraints on egg discrimination and cuckoo-host co-evolution

Rejection of cuckoo eggs in relation to host age: a possible evolutionary equilibrium

Learning to recognize nestlings is maladaptive for cuckoo Cuculus canorus hosts

Evolution of cooperation between individuals

Experimental evidence for offspring learning in parent-offspring communication.