Unraveling the History of Human Hair

iStock/ValuaVitaly
iStock/ValuaVitaly

Be it brown or blond, in a straight or naturally curly hair style, the hair that grows from our heads is a fundamental aspect of the human appearance. Our multitude of hair types is so ubiquitous that it’s actually easy to ignore how weird hair is—and not in the sense that your hair style might be on the wrong side of edgy.

“When it comes to human uniqueness, people come up with all kinds of stuff—culture, intelligence, language,” Tina Lasisi, a doctoral candidate in anthropology at Penn State University, tells Mental Floss. “[But] we’re the only mammals that have hairless bodies and hairy scalps.”

On the surface, our hair types are simple enough. Like fingernails, hair is made mostly of the protein keratin. It can survive for millennia under the right conditions—think Ötzi, the 5300-year-old iceman whose clothing, body, and hair were all preserved when he was frozen in a glacier. In warmer, wetter, more acidic environments, hair can degrade within weeks.

But that’s only what hair is. Why we have different hair types and how they came to be is a mystery that scientists are just now beginning to untangle.

Why Do We Have Hair on Our Heads?

Mother holding child with a braided hairstyle
iStock/Kali9

Some researchers have tried on various hypotheses to explain the patterns of hair growth in Homo sapiens and why they differ so dramatically from our close relatives, like chimpanzees. Losing body hair meant we could sweat more, a cooling mechanism that “helped to make possible the dramatic enlargement of our most temperature-sensitive organ, the brain,” writes anthropologist Nina Jablonski in Scientific American. Other researchers hypothesized that the hair remaining on human heads helped hominins regulate body temperature when they became bipedal and started traveling long distances. Basically, scalp hair created a kind of built-in hat.

Hair doesn’t usually stick around for hundreds of thousands of years the way fossilized bones do. If scientists want to answer the question of how our hair evolved from full-body fur, they have to explore the human genome—and Lasisi found that surprisingly few have done so. That’s partially because of the time and expense of conducting genomic analysis to pinpoint which genes affect the production of hair. But it’s also because it wasn’t a question posed by earlier (male) scientists, according to Lasisi.

“They were like, ‘Oh yeah, hair, it’s sexy on women, it’s probably sexual selection.’ But there was no effort to look into it as a unique human trait because they were more interested in our large brains, bipedalism, and whatnot,” Lasisi says.

How Did Different Hair Types Come To Be?

Blond woman facing forsythia bush
iStock/lprogressman

Even the lack of categorization for hair types is telling. Contrary to what your shampoo bottle may say, there is no real classification system for different hair types. At least not yet.

“Most mammals have straight hair. Only human hair [in African and Melanesian populations] has this tightly coiled configuration. We tend to talk about hair as straight, wavy, curly, in some cases frizzy,” Lasisi says. “But it’s as if we were trying to do genetic studies on height saying, there are short people, medium people, and tall people, now find what genes are related to that.”

In other words, before she could even attempt to answer the question of which genes control the texture and color of hair, Lasisi had to figure out a system for defining those hair textures and colors. Lasisi set about creating a classification system that she eventually hopes to publish, which relies on microscopic analysis of curl radius and measuring precise amounts of melanin in the hair. She then tried to answer the first of many questions: Whether tightly coiled African hair evolved in response to the hot environment. While that research is still ongoing, she says the results may indicate something counterintuitive—the thicker the hair, the better insulator it is from heat.

What's the oldest human hair ever found?

Woman wearing African jewelry viewed from the back
iStock/FernandoPodolski

On the rare occasions when hair is preserved in the fossil record, it can be an incredible source of information about our ancestors’ health and behavior. In 2009, Lucinda Backwell and colleagues described the discovery of what appeared to be human hair in fossilized hyena poop (a.k.a. coprolites) from more than 200,000 years ago—the oldest evidence of human hair to date. Five years later, Backwell and others followed that study with an examination of 48 hairs from hyena coprolites that identified several mammalian species. The presence of all those types of hair mean the hyenas were scavenging from many different remains, including humans.

“In the case of the human hairs in the coprolite, they told us a lot, because there were no bones,” Backwell, an anthropologist with the University of Witwatersrand in South Africa and Instituto Superior des Estudios Sociales, CONICET in Argentina, tells Mental Floss by email. They revealed that humans shared the environment with big herbivores like impala, zebra, kudu, and warthogs in southern Africa 200,000 years ago. Unfortunately for scientists, all of the keratin in that hair sample had been replaced by calcium carbonate that didn’t include any DNA. “The first prize would be to extract DNA and identify whether the hair belonged to a modern or archaic human, or even someone like Homo naledi, with its primitive features and young age,” Backwell said. In addition to helping identify the precise species of hominin, DNA from a hair sample like this could go a long way in telling more about different species’ relationship to one another.

Backwell has also studied human hair found in a high-altitude cave site in Argentina, one of the best environments for preserving hair because it’s “cool, dry, dark, and with a neutral pH,” she says. Like the coprolite hairs in South Africa, dating and identifying hairs in Argentina will help Backwell and others understand the spread of humans across the world.

How Can Hair Shed Light on History?

Woman with brown wavy hair facing the ocean
iStock/lprogressman

When people are exposed to substances in the environment, their hair will retain some of the chemical signatures of those substances. Hair found in ice, in amber, and on mummies from arid regions around the world has allowed researchers to learn fascinating details about the inhabitants of particular regions.

In 2013, archaeologists at the University of Chile analyzed 56 mummy samples found in northern Chile. Using gas chromatography-mass spectrometry (a tool that identifies different substances in a sample—and also happens to be used for drug testing), they found that people had smoked nicotine-containing plants continuously from 100 BCE to 1450 CE. “Overall, these results suggest that consumption of nicotine was performed by members of the society at large, irrespective of their social and wealth status,” the researchers wrote in their study.

Another group of archaeologists collected hair samples from 40 mummies found in Peru, Chile, and Egypt to analyze pre-industrial mercury concentrations across the world, ranging in time from 5000 BCE to 1300 CE [PDF]. Their results, published in 2018, indicated much lower levels of mercury in the environment than in the industrial era. Researchers also discovered that each group’s diet determined the actual level of mercury exposure—the Chilean mummies had higher concentrations from their seafood-based diet, while the Egyptians, who ate land animals, had the lowest.

For now, the mystery of hair’s evolution remains partially unsolved. But the next time you’re at the salon, look in the mirror and remember: Hair is part of what makes us human.

Not-So-Fancy Feast: Your Cat Probably Would Eat Your Rotting Corpse

Tycson1/iStock via Getty Images
Tycson1/iStock via Getty Images

Cat enthusiasts often cite the warmth and companionship offered by their pet as reasons why they’re so enamored with them. Despite these and other positive attributes, cat lovers are often confronted with the spurious claim that, while their beloved furry pal might adore them when they’re alive, it won’t hesitate to devour their corpse if they should drop dead.

Though that’s often dismissed as negative cat propaganda spread by dog people, it turns out that it’s probably true. Fluffy might indeed feast on your flesh if you happened to expire.

A horrifying new case study published in the Journal of Forensic Sciences offers the fresh evidence. The paper, first reported by The Washington Post, documents how two cats reacted in the presence of a corpse at Colorado Mesa University’s Forensic Investigation Research Station, or body farm, where the deceased are used to further forensic science for criminal investigations.

The study’s authors did not orchestrate a meeting between cat and corpse. The finding happened by accident: Student and lead author Sara Garcia was scanning surveillance footage of the grounds when she noticed a pair of cats trespassing. The cats, she found, were interested in the flesh of two corpses; they gnawed on human tissue while it was still in the early stages of decomposition, stopping only when the bodies began leaching fluids.

The cats, which were putting away one corpse each, didn’t appear to have a taste for variety, as they both returned to the same corpse virtually every night. The two seemed to prefer the shoulder and arm over other body parts.

This visual evidence joins a litany of reports over the years from medical examiners, who have observed the damage left by both cats and dogs who were trapped in homes with deceased owners and proceeded to eat them. It’s believed pets do this when no other food source is available, though in some cases, eating their human has occurred even with a full food bowl. It’s something to consider the next time your cat gives you an affectionate lick on the arm. Maybe it loves you. Or maybe it has something else in mind.

[h/t The Washington Post]

Wolf Puppies Play Fetch, Too, Study Finds

Christina Hansen Wheat
Christina Hansen Wheat

It took thousands of years of selective breeding for wolves to become the Golden Retrievers you see at dog parks today. Domesticated dogs are very different from their wild counterparts, but according to a new study, they may have a surprising trait in common. Researchers found that some wolf puppies are willing to play fetch with total strangers, suggesting that following human commands is intrinsic to canines.

For their study in the journal iScience, researchers from Stockholm University in Sweden set out to find how domestication affects behaviors in young wolves. They raised litters of wolf and dog pups separately from 10 days old and placed them in various scenarios.

When the scientists tested how the wolf puppies would respond to a game of fetch, they expected to be ignored. Chasing a ball and bringing it back requires understanding human commands and obeying them—abilities that were thought to only have emerged in dogs post-domestication.

The first two wolf groups met expectations by showing little interest in the toy, but something different happened with the third set. Three eight-week old pups went after the ball and brought it back when they were encouraged to do so. This was the case even when the person giving the commands was someone they had never met before.

Even though most of the puppies didn't play fetch, the fact that those who did belonged to the same litter indicates a "standing variation" for a retrieving trait in wolves. "When you talk about a specific trait in the context of standing variation, it means that there is variation for the expression of this trait within a given population," co-author Christina Hansen Wheat tells Mental Floss. "For our study it suggests that, while probably rare, standing variation in the expression of human-directed behavior in ancestral populations could have been an important target for early selective pressures exerted during dog domestication." In other words, ancient people seeking to domesticate wolves might have focused on some wolves' innate ability to follow human commands.

The first dogs were domesticated as far back as 33,000 years ago. Over millennia, humans have selected for traits like loyalty, friendliness, and playfulness to create the modern dog, but these new findings could mean that the dog's earliest canine ancestors were genetically predisposed toward some of these behaviors.

"All three litters were brought up under identical and standardized conditions across years," Hansen says of the pups in the study. "With this significant effort to control the environmental conditions, it is likely that the differences in behavior across litters to some extent have a genetic basis."

After raising the dog and wolf litters for three years and completing that part of their study, the researchers will continue to analyze their data to see if there are any other adorable (or weird) traits the two groups share.

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