Old Dominion University
Human Adaptation and Variation
Dr. Elva Smith
24 November 2014
Human biological diversity encompasses much more than the characteristics seen by the naked eye. Our species walked new and unique paths to arrive at our present existence. Our journey resulted in the achievement of many innovative and unique physiognomies allowing us to survive and reproduce. What characteristics have our species evolved and which most greatly shaped our evolution by conferring additional advantages in survivorship? Although there are many remarkable ...view middle of the document...
I will conclude with the advantages and disadvantages of skin pigment.
As Charles Darwin once said, “It is not the strongest or the most intelligent that will survive but those who can best manage change.” Natural selection provides the best answer to geographical distribution of human skin color. Natural selection is the process by which the forms most fit to survive and reproduce in a given environment do so in greater numbers. Over the generations, the least fit organisms die out, and the favored types survive by producing more offspring. The role of natural selection in producing variation in skin color will elucidate the explanatory approach to human biological diversity.
Essential to understanding natural selection are phenotype and genotype. Phenotype is the organism’s evident biological characteristics. Over the years, this develops as the organism is influenced by the environment. Genotype refers to the hereditary factors which includes chromosomes and genes. In continuance, traditional racial classifications assumed that biological characteristics were determined by heredity. Contemporary findings, however, prove otherwise.
Skin is a complex biological trait and is influenced by several genes. One of the primary determinants of human skin color is melanin. Melanin is a chemical substance manufactured in the epidermis, or outer layer of skin. To have a better understanding of variation of skin color, pigment is determined by the amount and size of melanin. For example, darker skinned people produce more and larger granules of melanin than light skinned people. Melanin protects from an assortment of maladies and is offered by screening out radiation from the sun. With the amount of sun absorbed by the body and the volume of melanin produced it is important to incorporate location when comparing skin color. With geographical distribution in mind, it combines with natural selection to play a role in the vast variety of skin pigments around the world to accompany survival in different climates.
The human body readily responds to changing environmental stresses in a variety of biological and cultural ways. We can acclimatize to a wide range of temperature and humidity. The nature of skin color distribution suggests an association with environmental factors varying with latitude. The association between dark skin color and a tropical habitat existed throughout the Old World due to the majority of the world’s dark skinned population residing in the tropics. The tropics are 23 degrees north and south of the equator.
Humans and their ancestors have been inhabitants of that land for thousands of years until migration to all corners of the globe started to occur. As migration continued so did natural selection. Outside of the tropics, in locations such as the poles, skin variation is different due to the lack of sun and is quite obvious. Adaptation to lighter pigmentation may have been driven by a need to increase UV...