This vegetarian apeman had a big, flat face with a massive jaw. It lived at a time when forests were vanishing from East Africa, creating a shortage of food such as soft fruit.

Paranthropus boisei coped with the shortage by evolving a massive jaw and huge teeth to chomp tough-to-chew foods such as nuts, roots, seeds and tubers.

These hard, gritty foods were more abundant in the open woodland and grasslands that boisei called home.

Paranthropus boisei may have lived in groups organized in harems, in which one male mated with many females. Males were easy to spot amongst a harem of females; they were much more muscular with much bigger faces.