Human Evolution and Animal Extinction

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Table of Contents

Homo Sapiens Invasions
Hunting
Habitat Loss
Environment Change
Mutations
References

Homo Sapiens Invasions

The evolution of human beings on Earth was a complicated process related to animal extinctions. Some scholars connect the latter to human activities, while others explain everything by natural conditions’ changes. The recent scholarly findings prove that invasions of Homo sapiens to the Austronesian and American continents were the major factors that conditioned the extinction of numerous animal species (Carroll, 2001, pp. 81 – 82). These data allow at least hypothesizing that the recent scholarly findings bring the science closer to defining actual causes of animal species extinction, unknown to the prior scholars.

Hunting

Hunting that was widely practiced by the Homo sapiens at the initial stages of their development is considered to be one of the main causes of animal extinction (University of Exeter, 2008). The findings of scholars from the University of Exeter seem to prove that hunting, but not climate change or any other naturally conditioned factors, caused the extinction of giant marsupials, also known as the Austronesian megafauna (University of Exeter, 2008). Prior scholarly views on climate change as the main extinction cause were based on the data that giant marsupials in the Austronesian continent became extinct 46,000 years ago, while humans came to the continent only 43,000 years ago.

However, recent research proved that some marsupial species were observed in the continent 41,000 years ago, i. e. 2,000 years after the Homo sapiens arrived. At the same time, the climate did not change essentially during those years, while hunting became used extensively, which allows scholars to argue about hunting as the major extinction factor (University of Exeter, 2008).

Habitat Loss

Further on, Klein (2002) argues about four other causes of animal extinction, and all of them are human-related. These four extinction factors are habitat loss, natural mass extinction, environmental pollution, and the combination of the first three that resulted in species mutations (p. 376). Habitat loss is argued to be the main of those four reasons, and again, it was caused by extensive human activities. Hunting provided Homo sapiens with food and improved their living conditions. The latter impacted the population growth and the need for large settlements (Klein, 2002, p. 378). As a result, the natural habitats of numerous animal species were destroyed to provide living space to human beings.

Environment Change

The pollution of the environment is thus the second most important extinction factor. Klein (2002) calls the Homo sapiens to be the dirtiest animal species on Earth and supports the point with substantial evidence (p. 378). From such a discussion, one can conclude that the waste that human activities bring to the environment makes the life of other species impossible in their natural habitats or in other places where living conditions were acceptable before human beings arrived.

Mutations

Finally, the sum of all the above factors might have caused the mutation of animal species and conditioned their subsequent extinction (Carroll, 2001, p. 182; Klein, 2002, p. 391). The point can be better illustrated by the Allele frequency and relative fitness equations.

Thus, supposing that before the effects of human activities conditioned the extinction of giant marsupials in the Austronesian continent a sample of ten of these animals had only AA or Aa genotypes (AA, AA, AA, Aa, AA, Aa, Aa, Aa, Aa, AA), their Allele frequency will be:

pA = 2 + 2 + 2 + 1 + 2 + 1 + 1 + 1 + 1 + 2 / 20 = 0.75 = 75%
pa = 0 + 0 + 0 + 1 + 0 + 1 + 1 + 1 + 1 + 0 / 20 = 0.25 = 25%

So, we can assume that the AA genotype was the natural genotype of the Austronesian marsupials. However, the human activities changed the genotype and increased the number of aa genes into the population (AA, aa, aa, Aa, aa, aa, Aa, Aa, aa, AA):

pA = 2 + 0 + 0 + 1 + 0 + 0 + 1 + 1 + 0 + 2 / 20 = 0.35 = 35%
pa = 0 + 2 + 2 + 1 + 2 + 2 + 1 + 1 + 2 + 0 / 20 = 0.65 = 65%

Thus, it is obvious that human activities might have changed the genotypes of the animals, deprived them of their natural qualities, and cause their extinction. Further on, the relative frequency of the genes also proves this point. The absolute frequency before and after the human invasion is supposed to be:

Before	After
WAA= 5	WAA= 2
WAa= 5	WAa= 3
Waa= 0	Waa= 5

Accordingly, the relative frequency before the human invasions was always the highest (1), while after the invasions it changed to 0.4 and 0.6 in AA and Aa types respectively, while the mutated genotype aa acquired the highest relative frequency 1. So, the effects of human activities seem to be more important for animal extinctions than climate change and other natural conditions.

References

Carroll, Sean. From DNA to diversity: molecular genetics and the evolution of animal design. London: Wiley-Blackwell, 2001. Print.

Klein, Jan. Where do we come from?: the molecular evidence for human descent. NY: Springer, 2002. Print.

The University of Exeter. Humans Implicated In Prehistoric Animal Extinctions With New Evidence. Science Daily, 2008. Web.

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Human Evolution and Animal Extinction

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