Evolution of eusociality

Eusociality evolved repeatedly in different orders of animals, particularly the Hymenoptera (the wasps, bees, and ants). This 'true sociality' in animals, in which sterile individuals work to further the reproductive success of others, is found in termites, ambrosia beetles, gall-dwelling aphids, thrips, marine sponge-dwelling shrimp (Synalpheus regalis), naked mole-rats (Heterocephalus glaber), and the insect order Hymenoptera (which includes bees, wasps, and ants). The fact that eusociality has evolved so often in the Hymenoptera (between 8 and 11 times), but remains rare throughout the rest of the animal kingdom, has made its evolution a topic of debate among evolutionary biologists. Eusocial organisms at first appear to behave in stark contrast with simple interpretations of Darwinian evolution: passing on one's genes to the next generation, or fitness, is a central idea in evolutionary biology. Current theories propose that the evolution of eusociality occurred either due to kin selection, proposed by W. D. Hamilton, or by the competing theory of multilevel selection as proposed by E.O. Wilson and colleagues. No single trait or model is sufficient to explain the evolution of eusociality, and most likely the pathway to eusociality involved a combination of pre-conditions, ecological factors, and genetic influences. Eusociality Eusociality can be characterized by four main criteria: overlapping generations, cooperative brood care, philopatry, and reproductive altruism. Overlapping generations means that multiple generations live together, and that older offspring may help the parents raise their siblings. Cooperative brood care is when individuals other than the parents assist in raising the offspring through means such as food gathering and protection. Philopatry is when individuals remain living in their birthplace. The final category, reproductive altruism, is the most divergent from other social orders. Altruism occurs when an individual performs a behavior that benefits a recipient in some way, but at the individual's own expense.