Evolution

Nature offers species a panoply of ways to determine an organism’s sex. That flexibility suggests we need not be concerned about losing sex chromosomes, but it raises the question of why such a fundamental property is so variable.

The polymath Christoph Adami is investigating life’s origins by reimagining life as self-perpetuating information strings.

Scientists have begun to identify the symphony of biological triggers that powered the extraordinary expansion of the human brain.

The biologist Joan Strassmann discusses cooperation in social insects, how amoebas can teach us about competition, and why the definition of “organism” needs an overhaul.

A single genetic change and some clever geometry show how single-celled organisms can band together to form cooperative multicellular entities.

A newly discovered class of microbe could help to resolve one of the biggest and most controversial mysteries in evolution — how simple microbes transformed into the complex cells that produced animals, plants and fungi.

The biologist Nancy Moran has spent a career investigating the surprising nature of symbiosis, a phenomenon in which two species can appear to merge into one.

A new understanding of viral swarms is helping researchers predict how viruses will evolve and where disease is likely to spread.

Emerging data suggests the seemingly impossible — that mysterious new genes arise from “junk” DNA.