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The human face is unique and universal, mechanical and expressive, modern and old. For more than 4 million years, our features have slowly transformed into what we see today in the mirror, a brief step on the way to who knows what.
From early hominins to modern Homo sapiens, a new review written by renowned experts traces the history of the human face through millions of years, according to landscapes, climates and cultures.
Like many of them, the international team is of the opinion that food and climate are important factors in the formation of the human face. Yet there is another element that, in their view, is too often neglected: social necessity.
"We know that other factors such as diet, respiratory physiology, and climate have helped shape the modern human face," says anatomist Paul O. Higgins of the University of York, "but one must interpret its evolution only factors would be an oversimplification."
Using the skin of the face, bones and muscles, modern humans can report more than 20 different categories of emotions. And that's not something we could always do.
As the human face evolved over millennia, it went from a rigid mask to an easy-to-handle cup: "a short-faced skull with a large, globular brain case," as the saying goes authors.
At the dawn of a smooth front, our eyebrows were officially unleashed with plenty of room for movement; at the same time, our faces have become smaller and thinner, allowing for subtle emotions like recognition and sympathy.
Suddenly, opportunities for gestures and non-verbal communication increased – an essential step for humans to build and maintain vast social networks.
"We think that improving social communication was a likely consequence of the face becoming smaller, less robust and with a less pronounced eyebrow," said one of the authors, Rodrigo Lacruz, a craniofacial biologist at the New York University.
"This would have allowed for more subtle gestures and therefore improved nonverbal communication."
It is doubtful that social communication could have reshaped the modern human face, but the authors think that it should at least be included in the main theories.
Food, for example, is one of the most cited factors to explain the shape of our face. Unlike modern humans, early hominins ate difficult plant foods, tearing them with their only teeth. As such, they needed large jaw muscles and these massive attachments required large, deep faces.
Over the last two million years, however, humans have started using tools to break down and cut our food. And as we learned to prepare and cook, our face began to shrink.
(Lacruz et al., Nature, 2019)
"Modern regimes and more moderate industrialized societies can mean that the human face continues to decline," says O. Higgins.
"There are limits to what the human face can change, for example, breathing requires a large enough nasal cavity."
This is a trend that has lasted for about 100,000 years and with the growing change in the climate problem, it could also be affected.
The authors say that temperatures could increase, which could change our appearance. If weather forecasts are correct, they claim that we could expect changes in our nasal cavities, which helps to warm and moisten the air before it gets into our lungs.
"We are a product of our past," says William Kimbel, expert in human evolution, at Arizona State University.
"Understanding the process by which we became human gives us the right to look at our own anatomy with wonder and ask what are the different parts of our anatomy that tell us about the historical path to modernity."
This study was published in Nature Ecology and Evolution.
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