Seminar One
Biology, culture and psychology
Social systems

Standing on his front legs and rolling a ball of wildebeest dung, a male dung beetle in East Africa courts a female, who rides along on the rolling ball. At one point, when the ground is just right, he starts digging and the whole party slowly sinks underground. At a depth of several feet he stops, and the female deposits one or more eggs in the dung, which will serve as a rich food source. The young will also be safe from predators. Dung beetles are unsung heroes of nutrient recycling and soil turnover in the tropics; we wear colorful ones on our bodies in the form of scarab jewelry.

Naked mole-rats live in large underground colonies in East Africa. They are among the most unusual mammals in the world, almost hairless and almost blind, with only one reproductive female in the colony and several reproductive males. The other colony members perform tasks such as digging tunnels; they forgo reproduction. What does this social organization have in common with eusocial insects such as ants, bees, wasps, and termites?

Orange clownfish find protection in an anemone with stinging tentacles on a coral reef in the Philippines; they are not harmed by the tentacles, as some predators would be. The breeding female is largest and the breeding male second largest. If the female dies, the male changes sex and takes her place, and the largest nonbreeder becomes the breeding male. These fish are born with a hermaphroditic potential and express only one of the two gender choices at any one time, depending on social stimuli.

An army of hungry mouths awaits any small animal that crosses this flooded area in the Brazilian Pantanal, their eye reflections shining in our strobe light as we look down from a low bridge. These are Pantanal caimans, crocodilians about five or six feet long. As you can see, they congregate in groups to feed on prey at night. The river is spacious, and each caiman could stalk prey away from the others, but they assemble in groups. This is social behavior, and how does it evolve?