Geologists assume when they find molecules called sterols in soils or rocks they indicate the presence of plants, animals or fungi in ancient environments. But discovering how some bacteria also produce and modify sterols could change those interpretations.
Fossil study finds early human activity — not climate shifts — led to the systematic decline of large animals around the globe that predated human migration out of Africa. The findings add to concerns about continued biodiversity loss and the impact on ecosystems.
Examining body sizes of ancient and modern aquatic mammals and their terrestrial counterparts reveals that life in water restricts mammals to a narrow range of body sizes – big enough to stay warm, but not so big they can’t find enough food.