Many people believe that humans have conquered nature thanks to the wonders of civilization and technology. Some also believe that because we are different from other creatures, we have complete control over our destiny and do not need to evolve. Although many people believe this, it is not true.
Like other living beings, humans have been shaped by evolution. Over time, we have developed—and continue to develop—characteristics that help us survive and thrive in the environments where we live.
I am an anthropologist. I study how humans adapt to different environments. Adaptation is an important part of evolution. Adaptations are characteristics that give someone an advantage in their environment. People with those characteristics are more likely to survive and pass those characteristics on to their children. Over many generations, these characteristics become common in the population.
The role of culture
Human beings have two hands that help us use tools and other objects dexterously. We are able to walk and run on two legs, which frees our hands to perform these specialized tasks. And we have big brains that allow us to reason, create ideas, and live successfully with other people in social groups.
All these characteristics have helped humans develop culture. Culture includes all our ideas and beliefs, as well as our ability to plan and think about the present and the future. It also includes our ability to change our environment, for example by making tools and growing food.
Although humans have changed our environment in many ways over the past thousands of years, we continue to be modified by evolution. We have not stopped evolving, but we are now evolving in different ways than our ancient ancestors. Our environments are often modified by our culture.
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We usually think of an environment as the climate, plants, and animals of a place. But environments also include the foods we eat and the infectious diseases to which we are exposed.
A very important part of the environment is the climate and the conditions we can endure. Our culture helps us change our exposure to the weather. For example, we build houses and put stoves and air conditioners in them. But culture does not completely protect us from the extremes of heat, cold and the sun’s rays.
Here are some examples of how humans have evolved over the last 10,000 years and how we continue to evolve today.
The power of solar rays
Although the sun’s rays are important for life on our planet, ultraviolet rays can damage human skin. Those of us with fair skin are at risk for severe sunburn and equally dangerous types of skin cancer. Instead, those of us with more pigment in our skin, called melanin, have some protection from the sun’s harmful ultraviolet rays.
People in the tropics with dark skin are more likely to thrive under frequent, bright sunlight. However, when ancient humans moved to cloudier, cooler places, dark skin was not necessary. Dark skin in cloudy places blocked the production of vitamin D in the skin, which is necessary for normal bone growth in both children and adults.
The amount of melanin pigment in our skin is controlled by our genes. So in this way, human evolution is driven by the environment—sunny or cloudy—in different parts of the world.
The food we eat
Ten thousand years ago, our human ancestors began domesticating animals such as cattle and goats to eat their meat. Then, around 2,000 years later, they learned to milk cows and goats to obtain this delicious food. Unfortunately, like most other mammals at the time, adult humans could not digest milk without feeling sick. However, some people could digest milk because they had genes that allowed it.
Milk was such an important food source in these societies that people who could digest it were more likely to survive and have many children. So the genes that allowed them to digest milk increased in the population until almost everyone could drink milk as adults.
This process, which occurred and spread thousands of years ago, is an example of what is called cultural and biological coevolution. It was the cultural practice of milking animals that led to these genetic or biological changes.
Other people, like the Inuit in Greenland, have genes that allow them to digest fats without heart disease. The Turkana people raise livestock in a very dry part of Africa, in Kenya. They have a gene that allows them to go long periods without drinking much water. This practice would cause kidney damage in other people because the kidney regulates water in the body.
These examples show how the remarkable diversity of foods people eat around the world can affect evolution.
Diseases that threaten us
Like all living beings, humans have been exposed to many infectious diseases. During the 14th century, a deadly disease called bubonic plague struck and spread rapidly throughout Europe and Asia. It killed about a third of the population in Europe. Many of those who survived had a specific gene that gave them resistance against the disease. Those people and their descendants were more likely to survive the epidemics that followed for several centuries.
Some diseases have hit recently. COVID-19, for example, swept the world in 2020. Vaccines saved many lives. Some people have a natural resistance to the virus based on their genes. It may be that evolution increases this resistance in the population and helps humans fight future virus epidemics.
As humans, we are exposed to a variety of changing environments. And so evolution in many human populations continues through generations, even now.
About the author:
Michael A. Little is Distinguished Professor Emeritus of Anthropology, Binghamton University, State University of New York.
This text was originally published on The Conversation.
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