New Delhi, July 28 -- NAIROBI - On the eastern shore of what is now Lake Turkana, a group of eight individuals moved through soft sediment 1.43 million years ago. Most were adult males. They moved together, and what they pressed into the volcanic ash-laced mud survived them by more than a million years. Twenty-one footprints from those eight individuals were published Monday in the Proceedings of the National Academy of Sciences, and they are revising the scientific understanding of a species long cast as a secondary figure in human evolution.

The species is Paranthropus boisei, a hominin that shared the African landscape with Homo erectus during the early Pleistocene. For decades, P. boisei was understood as robust but slight, with wide...