A 437-million-year-old fossil from a deposit in Wisconsin could be the oldest species of leech ever found.
Families of people with severe autism say the repeated expansion of the diagnosis pushed them to the sidelines. A new focus on the disorder has opened the way for them to argue their cause.
The E.P.A. plan would allow grocery stores, air-conditioning manufacturers and others to phase out hydrofluorocarbons in cooling equipment more slowly.
The new research provides evidence that Covid reinfections can increase the risk of long-term health consequences.
The discovery of huge petroglyphs of camels and donkeys, as well as hundreds of engraving tools, hints at complex early settlement in the region following the Ice Age.