|The creation of clothes and shelters will also have contributed greatly to survival without fur / Photo by Getty Images|
When we look around the animal kingdom, we can see most of our fellow mammals, including our pets, covered from head to toe in fur. Although we may be more intelligent than most of them, humans are still a part of the animal kingdom. So, where’s our fur?
Scientists have several explanations and theories as to why humans have lost their fur, and all of them try to justify that over the course of several millennia, it had become more advantageous for humans if they had lost most of their body hair.
Not Completely Hairless
While most of the hair had to go, certain places continue to grow plenty of hair. The tops of our heads have hair to provide cover from the Sun’s rays and to provide a bit of heat in the cold. Some areas, such as our armpits, continue to have hair to reduce friction. Armpit and pubic hair may have stayed to enhance odors that can provide social and sexual attraction among communities.
It was found by scientists that an inhibitor protein called Dickkopf 2 or Dkk2 may be fundamental to controlling hair growth in mammals. When tested on mice, they found that an increase of the protein blocked a signaling pathway that allowed for hair growth. This may be the thing that caused humans to stop growing so much hair, but why did it stop in the first place?
Adaptation to Survive
First is the aquatic-ape hypothesis. It states that anytime from 6 to 8 million years ago, the ancestors of humans today began to diversify their source of food as the dry seasons came, and began wading in shallow waters to look for fish and other marine animals to eat. As fur is detrimental to shallow water hunting and swimming, the body evolved to lessen the fur and to replace it with high amounts of fat, which can be seen in other aquatic mammals, as well.
According to Smithsonian.com, the theory even supports the fact that humans developed bipedalism, or walking on two legs, as this would have made it easier to wade across the water. Unfortunately, it seems that there is no clear evidence to support this theory, even for those studying paleontology.
Second is that humans lost their fur in order to better control their body temperature as they traversed through and lived in arid areas, such as savannas and deserts. The common ancestors of apes were used to living in cool forests, but as the ancestors of humans began to travel more, they would not have been able to live comfortably in the Sun all day. This is also the reason that sweat glands increased in number throughout the body to keep humans cool. The downside to this is that while humans did not lose much heat in the day, it was harder to retain on cold evenings when the body needed it.
Another interesting theory is that fur was discarded by our evolutionary line in order to greatly reduce the number of exo-parasites, such as ticks and lice, which would find a home in fur. Aside from being generally irritating, many parasites were capable of carrying diseases and viruses with them, such as Lyme disease and malaria, which could cause a great decline in health and even death in some cases, as explained by Scientific American.
The reduction of fur may have also coincided with the discovery and use of fire by humans, as they would have needed some method to adapt to the lowered temperatures in the evening without relying on their fur. The creation of clothes and shelters will also have contributed greatly to survival without fur. Looking at another hairless mammal, the naked mole rat, it can be easy to see the correlation. They live underground in tunnel colonies. Though parasites would usually abound in these areas, they evolved to have no fur which kept the parasites away, and the warmth of their bodies plus the shelter of their underground homes protect them from the elements.
|The reduction of fur may have also coincided with the discovery and use of fire by humans / Photo by Getty Images|
Indicator of Health and Sexual Attraction
An intriguing hypothesis is that hairlessness paved the way for better emotional communication between human beings. Scientists have found that most mammals have two cones in their eyes for detecting color, but humans have three. The third one, however, does not seem to be useful for hunting or tracking, but in detecting changes in the shades of a person’s face. In order to better see these, humans developed less hair and a better ability to detect emotional and health changes, which would manifest in a person’s cheeks and other areas with bare skin. Children with bluish or grayish hues may indicate illness, while a blush on the cheeks could signal sexual attraction.
As hair disappeared from our bodies, it changed the way that humans selected their mates, as those with smooth and clear skin would have been seen as an indicator of good health. This would have increased one’s sexual appeal. This could also explain why women are naturally less hairy.
Though we may still often believe we’re too hairy as we are now, perhaps we could all better appreciate the evolutionary changes when we consider we could’ve all been as hairy as our ape cousins.