Newly discovered fossil documents small-scale evolutionary changes in an extinct human species

Males of the extinct human species Paranthropus robustus were thought to be substantially larger than females — much like the size differences seen in modern-day primates such as gorillas, orangutans and baboons. But a new fossil discovery in South Africa instead suggests that P. robustus evolved rapidly during a turbulent period of local climate change about 2 million years ago, resulting in anatomical changes that previously were attributed to sex.