The human face is unique yet universal, mechanical yet expressive, modern yet ancient. For over 4 million years, our features have slowly morphed into what we see today in the mirror, a brief stop on the way to who knows what. From early hominins to modern Homo sapiens, a new review written by leading experts traces the history of the human face across millions of years, as landscapes, climates, and cultures come and go. Like many before them, the international team agrees that diet and climate were important factors in shaping the human face. Still, there’s another element they think is too often overlooked: social necessity. “We know that other factors such as diet, respiratory physiology, and climate have contributed to the shape of the modern human face,” says anatomist Paul O’Higgins from the University of York, “but to interpret its evolution solely in terms of these factors would be an oversimplification.” Using facial skin, bones, and muscles, modern humans can signal more than 20 different categories of emotion to one another. And that’s not something we could always do. As the human face evolved over millennia, it went from a s...