A new study theorizes that evolution ticks at different speeds, especially when a big group of organisms first appears.

"I'm stunned." says Per Ahlberg of Uppsala University, who coordinated the study; "A single track-bearing slab, which one person can lift, calls into question everything we thought we knew about when ...

A digital reconstruction of a million-year-old skull suggests humans may have diverged from our ancient ancestors 400,000 years earlier than thought and in Asia, not Africa, a study found. The ...