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Did the Feet of Homo Erectus Stink, Too?

Why we’ve got feet, when we got them, and why we hate them.

1.5 Million Year-Old Footprint


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There is no trace of stinky feet smell in the first clear human footprint. Found among many less clear footprints in Northern Kenya on foot trails in sedimentary rock dated to 1.5 million years ago, the footprint showed a rounded heel, an arch and a big toe that is not opposable like an ape’s. So it’s a pretty safe bet that this was not left by a tree climber. It was left by someone who stood up straight and walked in a very human way. In other words, it was an early form of homo erectus, the first close human relative to have the same body proportions as modern humans.

The apparently modern structure of this 1.5 million year old print suggests that, already, humans might have been able to run long distances. If so, that ability may have helped them scavenge carcasses. Imagine you are an early human. Shortly after mid-day you see vultures circling overhead at a distance. You run—and with luck you beat the local hyenas to the prize, because they won’t come out until night falls. 

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Early humans may have liked their feet unequivocally.

The ability to run for long distances would have also helped in what’s called “persistence hunting.”  In modern persistence hunters, the technique takes advantage of the fact that humans aren’t covered with thick fur and therefore don’t overheat as quickly as many animals. In the mid-day heat, humans chase animals and exhaust them so that they can be killed more easily. Persistence hunting requires significant intelligence. Because there might be long periods of time when the prey was out of sight, the human would need to be able to track the prey. It’s unclear whether 1.5 million years ago humans were sufficiently developed cognitively to hunt by this method. 

The First Shoes.

People who wear shoes regularly walk differently from those who go barefoot. Changes in how they distribute their weight get incorporated into their musculature and eventually into their bones.

The oldest known shoe is only 10,000 years old. But Erik Trinkaus, an anthropologist at Washington University in St. Louis, estimates that humans started wearing shoes around 40,000 years ago. He examined the skeletons of early humans and realized that, at about that time, human toes had started to shorten. Humans’ legs were still strong and thick. So were their feet. But their toes were by then, in his words, looking “wimpy.”

It may not be just a coincidence that, 40,000 years ago, human culture in Africa was going through lots of changes. People were creating artwork. Not long after then they were using tools like needles, which means they may have started wearing clothes. Some anthropologists speculate that there may have been enough people for a division of labor and the development of specialized skills, at least in settled communities. Who knows? There may even have been shoe-makers.

Stinky Feet

The stink is caused by bacteria that eat sweat and excrete a smelly waste.  But humans sweat all over. Why do our feet smell especially bad?

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By and large the bacteria on our feet are not necessarily the ones in our armpits, on our face, or on the backs of our knees. A University of Colorado study in 2009 found that each germ has its preferred place. The scientists figured this out by studying 27 different body sites including the gut, mouth, ears, nose, and skin on nine healthy adults. While certain kinds of bacteria could be found in more than one place, almost every place in the body housed more than one type of bacteria. It was the mix of bacteria—the bacterial soup, if you will—that was unique place by place. So it stands to reason that feet have a distinct smell; each human has armpmits witih its own, "home-made" bacterial soup. Armpits smell armpit-y for the same reason.

Sinky feet may have started 40,000 years ago when shoes first entrapped sweat and let bacteria feed. But although stinky feet may not be as old as the entire human evolutionary line, at least the father of evolutionary theory shared the problem with the rest of humanity. As a 12-year-old, he wrote about it in a letter to a friend. "I only wash my fett [sic] once a month at school, which I confess is nasty, but I cannot help it, for we have nothing to do it with."

Apparently it wasn’t easy in those days to get a nice tub of hot, soapy water all to yourself. In the developed world, at least, we've evolved beyond that problem. 

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By day Rebecca Coffey is a science journalist, contributing to Scientific AmericanDiscover, and Vermont Public Radio. She also presents a weekly radio spot, Family Friendly Science, on the nationally syndicated show, Daybreak USA. By night she is a novelist and humorist. Hysterical: Anna Freud's Story is due out in May 2014 from She Writes Press. Nietzsche's Angel Food Cake: And Other "Recipes" for the Intellectually Famished was published in October 2013 by Beck & Branch.

www.rebeccacoffey.com
Twitter: @rebeccacoffey

Rebecca Coffey is a science journalist and broadcast commentator with Vermont Public Radio. 

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