GOTHENBURG, SWEDEN—Søren Faurby of the University of Gothenburg and his colleagues suggest that hominins started triggering the extinctions of other creatures about four million years ago, according to a BBC News report. Faurby and his team compared the rate of extinction for large and small carnivores with environmental changes and the changes in brain size of human ancestors in East Africa such as Australopithecus, thought to have evolved some 4.2 million years ago, and Ardipithecus, estimated to have lived some 4.4 million years ago. The researchers found that the extinction rate of large carnivores correlated with the increasing brain size of human ancestors and changes in vegetation, but not with changes in precipitation or temperature. Faurby and his team members think early human ancestors may have stolen prey brought down by large carnivores, thus depriving them of food. For more on scavenging hominins, go to "Marrow of Humanity."