Scientists Explain: Why Humans Lost Their Fur — And What That Reveals About Human Evolution

Humans and apes both evolved from a common ancestor who lived millions of years ago, but why did they retain their fur, while humans lost theirs? Well, the answer to this type of question is evolution, and how we were changed over time by our environments and desire to survive.

In other words, humans lost their fur because it is necessary for them to do that; otherwise, the species would most likely not have lived on. While apes did not because the challenges from their environments they faced were different. Let’s dive deeper to understand the answer to the question of why humans lost their fur.

Cooling Down Under the Sun

Humans likely began to lose their fur slowly around 2 to 1.5 million years ago, until we reached the point that we look like who we are today. The most accepted theory is that when we moved from shaded forests into open savannas and grasslands, our dense fur became a liability.

While apes after the split from the ancestral species, most probably stayed in those forest areas, and did not need to lose their fur. Ancient humans needed to venture out for several reasons, such as climate change and to hunt for food.

After this crucial transition to a different environment, natural selection favored individuals with less body hair and more sweat glands, as it enables more efficient thermoregulation. The process by which we maintain our internal body temperature, despite the external temperature fluctuations.

Which means that when we are hunting for food, usually by persistence hunting and outrunning deer or antelopes, we need to stay cool enough not to pass out under the hot sun. This is why, over time, as we naturally selected for individuals with less hair, as they are the ones who are more likely to survive too, we ended up losing most of our fur.

Read more: Smithsonian Mag

Genes That Turned Off the Coat

How Humans Lost Their Fur

To avoid overheating while doing endurance activities, especially when hunting for food, ancient humans needed to lose their fur. This allows the sweat to evaporate directly from the skin, which is a far more effective way of cooling down.

However, even today, our evolutionary past is in our DNA. Some people still carry the genetic instruction for full-body hair, but the mutations in genes like KRTHAP1 and HR led to less hair production over time, which is why we do not have thick fur, even if we have that blueprint in our blood.

In other words, those mutations might have reduced our hair, but they did not delete the genes for full-body hair. Similar patterns can actually be observed in other mostly hairless mammals, which suggests that gene loss is a common evolutionary process.

Beyond Cooling—Parasites, Babies & Skin Health

Beyond just cooling our body temperatures during the hunt for food, or other endurance activities that we need to do millions of years ago, there are other theories that add to it.

Hair loss may have helped reduce parasite loads, therefore, avoiding some diseases that we could have gotten from them. It could have also improved the skin health as it is exposed to the sunlight, and allows better absorption.

There is also a theory called the “maternal selection” hypothesis, where losing fur allowed mothers to have skin-to-skin contact with their babies, becoming more attached and bonded. It could have increased the survival rate of infants, especially if their parents are more invested due to a greater desire to hold and carry their babies.

Read more: WIRED

What Fur Loss Shaped Beyond Hair

One of the funny things about evolution is that sometimes we needed the traits we lost due to some environmental shifts, like another ice age. So to compensate for lacking the thick fur to survive, humans adapted and developed technologies, like clothing and shelter.

Those simple things could have played a big role in how we came to be today. The little things add up over time, because although hypothetical, if we did not move away from the forests, we would not have lost our fur, and maybe we wouldn’t develop a shelter system, along with other ancient technological inventions.

The Shocking Truth About Why Early Humans Lost Their Fur!

Author's Final Thoughts

The study of how we lost our fur is also the study of human decision, influenced by our environments and needs for adaptation. It also shows how evolution is a mix of survival and innovation. These small changes ripple forward into bigger transformations in the future, shaping our society, culture, and eventually creating the modern civilization we know today.

Read more: Scientists Explain: If We Didn’t Evolve From Apes of Today, Then Where Did We Come From?

References & Further Reading

Wheeler, P. E. (1984). The evolution of bipedality and loss of functional body hair in hominids. Journal of Human Evolution. https://doi.org/10.1016/S0047-2484(84)80079-2

Rantala, M. J. (2007). Evolution of nakedness in Homo sapiens. Journal of Zoology. https://doi.org/10.1111/j.1469-7998.2007.00295.x

Best, A., & Kamilar, J. M. (2018). The evolution of eccrine sweat glands in human and nonhuman primates. Journal of Human Evolution. https://pubmed.ncbi.nlm.nih.gov/29544622/

Kamberov, Y. G., et al. (2013). Modeling recent human evolution in mice by expression of a selected EDAR variant. Cell. https://doi.org/10.1016/j.cell.2013.01.016

Jablonski, N. G., & Chaplin, G. (2010). Human skin pigmentation as an adaptation to UV radiation. PNAS. https://doi.org/10.1073/pnas.0914628107