What color were the first humans

The first humans emerged in Africa around two million years ago, long before the modern humans known as Homo sapiens appeared on the same continent.

Table of Contents Show

The First Humans
Early Humans, Neanderthals, Denisovans Mixed It Up
Human Evolution Was Messy
Early Human Ancestors Shared Skills
Shielding Naked Skin
Leaving the Tropics
From Light to Dark to Varied

There’s a lot anthropologists still don’t know about how different groups of humans interacted and mated with each other over this long stretch of prehistory. Thanks to new archaeological and genealogical research, they’re starting to fill in some of the blanks.

The First Humans

Homo habilis individuals chip away at rocks, sharpening them for cutting up game or scraping hides while a woman, with her child, gathers wild berries to eat and branches to make shelters.

Brown Bear/Windmil Books/Universal Images Group/Getty Images

First things first: A “human” is anyone who belongs to the genus Homo (Latin for “man”). Scientists still don’t know exactly when or how the first humans evolved, but they’ve identified a few of the oldest ones.

One of the earliest known humans is Homo habilis, or “handy man,” who lived about 2.4 million to 1.4 million years ago in Eastern and Southern Africa. Others include Homo rudolfensis, who lived in Eastern Africa about 1.9 million to 1.8 million years ago (its name comes from its discovery in East Rudolph, Kenya); and Homo erectus, the “upright man” who ranged from Southern Africa all the way to modern-day China and Indonesia from about 1.89 million to 110,000 years ago.

In addition to these early humans, researchers have found evidence of an unknown “superarchaic” group that separated from other humans in Africa around two million years ago. These superarchaic humans mated with the ancestors of Neanderthals and Denisovans, according to a paper published in Science Advances in February 2020. This marks the earliest known instance of human groups mating with each other—something we know happened a lot more later on.

Early Humans, Neanderthals, Denisovans Mixed It Up

After the superarchaic humans came the archaic ones: Neanderthals, Denisovans and other human groups that no longer exist.

Archaeologists have known about Neanderthals, or Homo neanderthalensis, since the 19th century, but only discovered Denisovans in 2008 (the group is so new it doesn’t have a scientific name yet). Since then, researchers have discovered Neanderthals and Denisovans not only mated with each other, they also mated with modern humans.

“When the Max Plank Institute [for Evolutionary Anthropology] began getting nuclear DNA sequenced data from Neanderthals, then it became very clear very quickly that modern humans carried some Neanderthal DNA,” says Alan R. Rogers, a professor of anthropology and biology at the University of Utah and lead author of the Science Advances paper. “That was a real turning point… It became widely accepted very quickly after that.”

As a more recently-discovered group, we have far less information on Denisovans than Neanderthals. But archaeologists have found evidence that they lived and mated with Neanderthals in Siberia for around 100,000 years. The most direct evidence of this is the recent discovery of a 13-year-old girl who lived in a cave about 90,000 years ago. DNA analysis revealed that her mother was a Neanderthal and her father was a Denisovan.

Human Evolution Was Messy

The human lineage of Australopithecus afarensis, Homo habilis, Homo erectus, Neanderthals and Homo sapiens.

Encyclopaedia Britannica/Universal Images Group/Getty Images

Scientists are still figuring out when all this inter-group mating took place. Modern humans may have mated with Neanderthals after migrating out of Africa and into Europe and Asia around 70,000 years ago. Apparently, this was no one-night stand—research suggests there were multiple encounters between Neanderthals and modern humans.

Less is known about the Denisovans and their movements, but research suggests modern humans mated with them in Asia and Australia between 50,000 and 15,000 years ago.

Until recently, some researchers assumed people of African descent didn’t have Neanderthal ancestry because their predecessors didn’t leave Africa to meet the Neanderthals in Europe and Asia. But in January 2020, a paper in Cell upended that narrative by reporting that modern populations across Africa also carry a significant amount of Neanderthal DNA. Researchers suggest this could be the result of modern humans migrating back into Africa over the past 20,000 years after mating with Neanderthals in Europe and Asia.

Given these types of discoveries, it may be better to think about human evolution as a “braided stream,” rather than a “classical tree of evolution,” says Andrew C. Sorensen, a postdoctoral researcher in archaeology at Leiden University in the Netherlands. Although the majority of modern humans’ DNA still comes from a group that developed in Africa (Neanderthal and Deniosovan DNA accounts for only a small percentage of our genes), new discoveries about inter-group mating have complicated our view of human evolution.

“It seems like the more DNA evidence that we get—every question that gets answered, five more pop up,” he says. “So it’s a bit of an evolutionary wack-a-mole.”

Early Human Ancestors Shared Skills

Human groups that encountered each other probably swapped more than just genes, too. Neanderthals living in modern-day France roughly 50,000 years ago knew how to start a fire, according to a 2018 Nature paper on which Sorensen was the lead author. Fire-starting is a key skill that different human groups could have passed along to each other—possibly even one that Neanderthals taught to some modern humans.

“These early human groups, they really got around,” Sorensen says. “These people just move around so much that it’s very difficult to tease out these relationships.”

The first modern humans evolved about 200.000 years ago in Africa. When they lost their body hair (or at least most of it), they needed some other protection of their skin from the sun - otherwise they are prone to develop melanoma. Melanin is such a protection, and the rate of melanoma is much lower in dark skinned people. There is also a nice correlation between latitude and skin color - the more to the north (and to some degree to the south as well) you get, the lighter the skin color of the population gets. The reason for this is likely the better ability to synthesize Vitamin D (for which you need sunlight on the skin):

The lightening of the skin occurred after humans moved to Europe:

The Timing of Pigmentation Lightening in Europeans

And we even know, that this occured more than once, since the genetic reasons for lighter skins are different between europeans and light skinned asians. A lot of this we know via sequence comparisions of genes involved in pigmentation, there you can trace mutations and see, where they show up first and how they migrate over time. One very good example is the melanocortin-1-receptor (MC1R), which is mutated pretty often in europeans (mutations in this gene are generally associated with lighter skin and hair color; people with red hair carry certain mutations in this gene) but its under selection pressure to not mutate in africa (there are almost no known mutations in MC1R for africans). Another example would be a mutation in the SLC24A5 gene, which is exclusively found in europeans, but not in asians and which accounts also for lighter skin. I stop here for the moment, if there are more specific question, go ahead.

Human skin color reflects an evolutionary balancing act tens of thousands of years in the making. There’s a convincing explanation for why human skin tone varies as a global gradient, with the darkest populations around the equator and the lightest ones near the poles. Put simply, dark complexion is advantageous in sunnier places, whereas fair skin fairs better in regions with less sun.

That may seem obvious, considering the suffering that ensues when pale folks visit the beach. But actually, humanity’s color gradient probably has little to do with sunburn, or even skin cancer. Instead, complexion has been shaped by conflicting demands from two essential vitamins: folate and vitamin D. Folate is destroyed by the sun’s ultraviolet (UV) radiation. Whereas the skin kickstarts production of vitamin D after being exposed to those same rays.

Hence, the balancing act: People must protect folate and produce vitamin D. So humans need a happy medium dosage of sun that satisfies both. While the intensity of UV rays is dictated by geography, the amount actually penetrating your skin depends on your degree of pigmentation, or skin color.

That’s the basic explanation, proposed in 2000 and fleshed out since by anthropologist Nina Jablonski and geographer George Chaplin. But for the full story of skin color, we’ve got to go way back to hairier days.

Shielding Naked Skin

Several million years ago, our ancestors’ skin tone would not have been obvious. That’s because early hominins were almost certainly cloaked in dark fur. But beneath the body hair, they probably had pale skin based on the fact that our evolutionary cousins, chimpanzees and gorillas, have light skin under dark fur today.

Our ancestors eventually lost this fur and gained pigment in their skin. Although the exact timing and causes are debated, many researchers agree that when humans lost their fur, it helped us stay cool while foraging as upright-walking bipeds in the sunny, open habitats of equatorial Africa. The tradeoff, however, was bare skin that was exposed to intense, year-round UV rays. In this context — roughly 1 to 2 million years ago — darker skin was likely better to protect folate stores.

Why is folate so important? The nutrient plays a role in DNA activities, but its major impact is on evolutionary fitness — one’s ability to survive and reproduce — through fetal development. When pregnant women don’t have enough folate, it can lead to neural tube disorders like spina bifida, a condition where the vertebrae do not fuse completely around the spinal cord. Most neural tube disorders are debilitating or fatal.

Experiments have shown that sunlight breaks down folate, as an isolated molecule, in blood plasma and in skin biopsies. It’s thought that dark skin impedes this because it contains higher amounts of melanin, a dark-brown pigment that absorbs UV rays and chemically disarms their harmful by-products.

Human skin color found in indigenous peoples varies with latitude. (Credit: Emmanuelle Bournay, UNEP/GRID-Arendal)

Leaving the Tropics

But the human lineage did not remain exclusively in equatorial Africa. At different times, people ventured both north and south, to higher latitudes with less sunlight.

That’s when vitamin D became a problem. Like folate, this vitamin is important for evolutionary fitness. It facilitates absorption of calcium, necessary for healthy bones and immunity. Vitamin D can be made in the skin, but only when the process is initiated by certain wavelengths of UV rays.

Away from the tropics, for most of the year, there is just not enough UV of the right wavelength for skin cells to form vitamin D. One study in the 1980s showed this using fresh foreskin collected from Caucasian babies circumcised in Boston. The researchers divided each sample in half. Then, they exposed one part of the foreskin sample to three hours of midday sun and kept the other in the dark. In the spring through fall months, the sun-exposed skin still produced the precursor for vitamin D, as would happen in a living human. However, no measurable precursor was synthesized during winter, up until March 17.

So, to get sufficient vitamin D year-round in high latitude places like Boston, people have to rely on body-stores built up during the summer months or acquire the nutrient through foods, like fatty fish. But the darker your skin, the harder it is to maintain adequate vitamin D. In studies comparing dark and light-skinned residents of northern cities, paler people had higher vitamin D levels throughout the year. Their less pigmented skin let in more rays.

From Light to Dark to Varied

A range of skin colors evolved at different times, in different populations, as human spread across the globe. In addition to these genetic biological changes, groups have also developed cultural adaptations to deal with variable sunlight. For instance, we can consume diets rich in folate and vitamin D. We can also build shelters, wear clothing and slather sunscreen to block UV rays.

Skin color is one of the most obvious and (literally) superficial ways humans differ. But the evolutionary story behind this variation is shared: Over the course of human evolution, complexion evolved from light to dark to a continuous gradient, mediated by geography, genes and cultural practices.