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Human Evolution and Adaptation to the Environment
Human evolution is the evolutionary process of change through which human beings originated from apelike ancestors to their current state. Over approximately six million years, scientific evidence has shown that human beings’ behavioral and physical traits have changed drastically due to various biotic and abiotic factors (Campbell, n. p). Evolution means that the human race had to change over time to adapt to the changing environment. The biotic and abiotic factors played a significant role in human evolution and continue to affect how people adjust to the changing environment. This essay will discuss the phenomenon of human adaptation to the environment and show whether human evolution and adaptation are still ongoing.
One of the most well-known scientists who studied evolution is Charles Darwin. In his theory about evolution, he stated that only the species which were able to adapt to the changing environment could survive the onslaught of evolution. This phenomenon he called “Survival for the Fittest.” Survival for the fittest applied for both animals and plants. Human beings, therefore, had to develop traits to enable them to cope with the harsh climates. In adapting to the environment, Charles Darwin and Alfred Wallace proposed two ways in which the traits in animals were developed. First is the positive natural selection, which is the tendency of a beneficial trait to increase in prevalence and enhances the chances of survival of the organism. It has two characteristics; it should be beneficial to the organism, and it should be inheritable. The second way is the negative natural selection, which decreases the chances of survival of an organism. For human beings to adapt to the changing environment, positive natural selection was highly required to ensure their survival. Some of these adaptations are shown below.
Malaria Resistance
Malaria is a dangerous disease that is known to exist in warm areas, especially between the tropics. As the weather changed from cold to warm, diseases such as malaria found their way into the environment. An increase in population density meant that the transmission of diseases among the people was much faster. With a lack of medication in that era, malaria became an agent of natural selection where multitudes of human beings died if they could not adapt to the disease (Schaff and Sabeti, 14). Through cell mutation, human beings slowly developed resistance to malaria. The resistance gene was inherited from parents to offspring. Those who possessed the gene were able to survive the disease while those without it perished in what Darwin called natural selection.
The ability of malaria to drive natural selection during human evolution does not come as a surprise because it is one of the oldest human diseases. Today, it remains the leading cause of death worldwide, with more than one million deaths of children in Africa alone each year. The result of the malaria resistance mutation is the sickle cell trait, which is resistant to malaria. It is a blood cell disorder resulting from mutation as a way of coping with malaria in the environment.
Pigmentation
Pigmentation can be referred to as the color of the skin or the different races we have across the world. African is known as the cradle of humankind. This means that all the other people in the world migrated from Africa, leading to the differentiation in skin color due to exposure to varying temperatures and sunlight. As Asians and Europeans moved northwards away from Africa, they experienced a change in the environment (Muehlenbein, n. p). The sunlight became less, and the temperature grew colder as they moved away further from the tropics. The new environmental factors exerted selective pressure on the migrating people. They experienced positive selection in numerous genes, which altered the number of skin pigments produced (Muehlenbein, n. p). This depended on the amount of sunlight exposure and the temperature of the surrounding areas. The colder temperature and shorter periods of sunlight exposure made it unnecessary to have a dark skin color. Therefore with time, their skins adapted to the environment, and the gene mutations resulted in the production of lesser skin pigments, resulting in various races.
Lactose Tolerance
Human beings greatly depended on wild animals and plants for food. However, about 10,000 years ago, they started the domestication of animals and plants, changing the human diet (Hancock et al., 8927). The individuals who quickly adapted to the digestion of the new foods had a selective advantage over the others. One of the well-known and documented adaptation of the new foods is lactose tolerance. This is the ability to digest lactose, a sugar found in milk. The ability to digest lactose disappears before adulthood in mammals, including human beings. However, after the domestication of cows and goats, adults stated taking milk, which made them adapt to the new food (Hancock et al., 8928). Gene mutation made it possible for the breakdown of lactose to persist to adulthood, enabling human beings to consume milk.
Many people may think that evolution came to an end with the modern man or Homo sapiens sapiens as scholars call it. However, the environmental changes experienced today have resulted in continuous evolution, which is likely to go on for many years to come. Earth continues to become warmer day by day, leading to shifting patterns of precipitation, droughts, and no longer growing periods. Animals and plants are evolving to cope up with the changing environment, so are human beings.
Evolution inside the Body
As the climate becomes warmer, diseases like malaria, West Nile virus, and other tropical diseases will start spreading to the temperate areas such as the United States and Europe (Behrensmeyer, 476). The people living in those temperate zones will be exposed to these diseases, which were predominantly found in warm areas. Therefore, their immune system will be forced to evolve in order to fight new infections. The changing diets may also trigger the altering of microbiomes – the microorganism and bacteria that live in our guts and help keep our bodies healthy (Behrensmeyer, 478). Meat eaters and vegetarians harbor a different mix of bacteria. The differences could be exaggerated by prolonged droughts, making it too expensive to raise livestock for meat.
External Changes
The evolutions inside the body will largely be invisible. However, as changes happen in the inside, some will be happening on the outside. Scientists believe that the changing climate will reduce racial differences by triggering massive migration (Behrensmeyer, 479). Recently, people have been moving to urban centers in coastal regions. On the other hand, global warming continues to melt more polar ice leading to sea-level rise; hence people will be forced to flee the coasts. As droughts become more severe, people will migrate from arid areas to places with adequate water supply. These migrations will eliminate geographic barriers that separate human beings. Actually, the process has already started with 258 million people living in foreign countries. World Bank estimates that climate change will lead to the migration of 140 million people by 2050 (Behrensmeyer, 479). The people who are more likely to migrate are those living in South Asia, Latin America, and sub-Saharan Africa.
Large scale migration will cause gene flow, a form of evolution resulting from the blending of genes among the people. The blending of genes will lead to children with a combination of traits not found in any parents. It is projected that in 10 generations to come (250 years), racism might slowly fade due to gene blending (Behrensmeyer, 480).
In conclusion, evolution is a continuous process in human beings. Therefore, people should be prepared to witness more changes as environmental factors change. Fewer distinctions between people of various regions are likely to be seen due to the warming climate. This is because most of the variations were caused by differences in temperature. In general, evolution will go on as long as human beings are still in existence.
Work Cited
Campbell, Bernard Grant. Human evolution: an introduction to man’s adaptations. Transaction Publishers, 1966.
Hancock, Angela M., et al. “Human adaptations to diet, subsistence, and ecoregion are due to subtle shifts in allele frequency.” Proceedings of the National Academy of Sciences 107.Supplement 2 (2010): 8924-8930.
Schaffner, S. F. P. C. S., and P. Sabeti. “Evolutionary adaptation in the human lineage.” Nature Education 1.1 (2008): 14.
Behrensmeyer, Anna K. “Climate change, and human evolution.” Science 311.5760 (2006): 476-478.
Muehlenbein, Michael P., ed. Human evolutionary biology. Cambridge University Press, 2010. https://learnuseast1prodfleet01xythos.s3.amazonaws.com/5cc71db6522fe/13589844?responsecachecontrol=private%2C%20maxage%3D21600&responsecontentdisposition=inline%3B%20filename%2A%3DUTF8%27%27Snake%2520venom%2520phylogeny.pdf&responsecontenttype=application%2Fpdf&XAmzAlgorithm=AWS4HMACSHA256&XAmzDate=20200525T210000Z&XAmzignedHeaders=host&XAmzExpires=21600&XAmzCredential=AKIAZH6WM4PLTYPZRQMY%2F20200525%2Fuseast1%2Fs3%2Faws4_request&XAmzSignature=4fcda18411b73b2fa1a5e1b6a38bd8cc7a5b5d73b8a76b95567da8b4ac90989b