Scientists purposefully made mice sick to test how the creatures’ intestines—and the microbes they harbor—would react. They discovered details behind a remarkable relationship that, when working well, keeps both parties healthy.

A fossil group of alleged evolutionary human ancestors called australopithecines—all quite ape-like in their features—have traditionally been uncooperative as transitional forms. Now the famous Taung child, a supposed example exhibiting early transitional developmental skull features has been debunked.¹