Evolution

In a year packed with fascinating discoveries, biologists pushed the limits of synthetic life, probed how organisms keep time, and refined theories about consciousness and emotional health.

Recent efforts to map every cell in the human body have researchers floored by unfathomable diversity, with many thousands of subtly different types of cells in the human brain alone.

Modern scientists aren’t content with predicting how life evolves. They want to shape it.

Paradoxically, natural selection can sometimes seem to block organisms from evolving useful adaptations. But a new study of “fitness landscapes” and antibiotic resistance in bacteria shows that life still finds a way.

Cells in the placenta have an unusual trick for activating gentle immune defenses and keeping them turned on when no infection is present. It involves crafting and deploying a fake virus.

A new analysis of ancient sediments fills a gap in the fossil record — revealing a massive dynasty of ancient eukaryotes, which may have reigned for 800 million years and shaped the history of life of Earth.

Why did mammals, grasses and some other groups of organisms explode in diversity only after millions of years? The evolutionary biologist Andreas Wagner plumbs the secrets of those “sleeping beauties.”

By watching “minimal” cells regain the fitness they lost, researchers are testing whether a genome can be too simple to evolve.

The reshuffling of neurons during fruit fly metamorphosis suggests that larval memories don’t persist in adults.