Natural selection

How does evolution select the fittest “individuals” when they are ecosystems made up of hosts and their microbiomes? Biologist debate the need to revise theories.

Some species have the equivalent of many more than two sexes, but most do not. A new model suggests the reason depends on how often they mate.

How the ultra-cooperative behavior of ants, bees and other social insects could have evolved continues to challenge formal analysis. But a new theory about hedging bets against nature’s unpredictability may change the math and shift the debate.

Scientists are exploring how organisms can evolve elaborate structures without Darwinian selection.