Human variation and adaptation
Human species portray many characteristics but the most notable characteristic is its variation and adaptation to this variations. Several approaches are used in the study of human variation and they include race, intelligence and physical characteristics. In this chapter the author looks critically at the causes of physical differences among modern human beings and how they bring about adaptability (Kottak, 2010). The author also looks at the concept of race and determines whether it is useful for studying human physical variation. He also determines whether there is any variation in intelligence from one population to another.
Physical characteristics that define a given population or an individual are as a result of interactions between genes and the environment. A good example which is used by the author to explain this phenomenon is that an individual’s genes predispose one to a particular skin color, but the individual’s skin is greatly affected by environmental factors such as the amount of solar radiation (Kottak, 2010). The author is quick to note that, despite the fact that the environment plays a big role in determining an individuals’ physical characteristics, variant forms of genes exists within the gene pool of Homo sapiens.
The author was for the opinion that the variability present in many animal species signifies a rich potential which can bring about new combinations of characteristics in future generations. Kottak also agues that a species growing up in specific dynamic environment can evolve genetically in such a way that it can produce individuals with characteristics suitable to its altered life. This is also another classical example of how genes interact with the environment. The author also brings in the idea of natural selection and states that many species fail to thrive in their new environments in that they don’t achieve reproductive success living those species with the favorable traits to reproduce and subsequently their genes predominate in the environment. He concludes that this phenomenon is what has made humankind to dominate a variety of environments (Kottak, 2010).
The author also looks on how different geographical regions around the world have contributed in human variation and adaptation. He highlights that selective pressures through the Pleistocene brought about diffentiation in animal life which is different from one geographical region to another. This is seen in the way skin color in distributed around the continents of the world in that populations of Homo sapiens living in the tropics were seen to have higher frequency of genes for dark skin than those in the northern region. Blood groups were also thought to be influenced by geographical regions where by frequency of blood group O is predominant in native Americans, blood group A tend to be predominant in certain European populations and type B tend to be highest in some Asian populations (Kottak, 2010).
The issue of race which was meant to refer to the diverse peoples is also analyzed by the author and he points out that it is difficult to use race as a way classifying Homo sapiens and the author just describes it as a social category. Some of the weaknesses of using this system for classification of humankind that are pointed out by the author are that there is misuse and misunderstanding of the term race and association with racism, the fact that humans have interbred in such a way that there is no distinct traits that can identify one with a specific race and he also agues that there is no agreement on how many genetic differences it takes to form s race (Kottak, 2010).
Intelligence is thought of to be influenced by environmental and genetic factors which make the author want to compare variations in intelligence among different populations but he finds no convincing evidence that populations vary with regard to intelligence.
The author also found it necessary to touch on palaeopathology which is the study of ancient diseases and the way they affect human body and way of life. In this area he explores the three major categories of diseases which are nutrition deficiencies, degenerative diseases and communicable diseases. The author explains that, throughout evolution different population groups are exposed to an array of diseases which exert selective pressures on the human population. As a result of this exposure, the diseases influence the occurrence of certain alleles that affect the immune response thus bringing about variation in humans. The high prevalence of infectious disease is linked to global warming, increased migration where by people interact through migration and in cases where communicable diseases are present, their spread to non infected populations becomes easy, excessive use of antibiotics in some regions which results to the emergence of drug resistance strains which in turn infect human beings resulting to more variations in humans such as carrier traits and the ever increasing human population which results to overcrowding which facilitates the spread of infectious diseases (Kottak, 2010).
As the human population is continually growing bigger and bigger so does its variation increase in an attempt to adapt to the ever changing environment. In regard to this phenomenon, the author is of the opinion that in course of human evolution, humans in all parts of the world were forced to rely on cultural instead of biological adaptation in order to survive. Development of a considerable physical variation arose as a result of the population spreading to other parts of the world. This was contributed by genetic drift and biological adaptation as a result of different climatic conditions.