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Domestication of Humanity
“Scientists have also found evidence for self-domestication in human skeletal remains. Based on what’s happened to animal domesticates, it’s predicted that skulls should have become smaller and more feminine looking (in both sexes) with reduced brow ridges. Indeed, that’s what a 2014 Current Anthropology paper found, which measured Homo sapiens skulls from the Stone Age to recent times, about 200,000 years of human evolution. These results agree with previous studies reporting that average skull — and by proxy brain — volume in Homo sapiens has decreased by roughly 10 percent in the past 40,000 years. ”
“The sustained selection for lowered reactivity among mammal domesticates has resulted in profound changes in brain form and function. The larger the size of the brain to begin with and the greater its degree of folding, the greater the degree of brain-size reduction under domestication.[12][42] Foxes that had been selectively bred for tameness over 40 years had experienced a significant reduction in cranial height and width and by inference in brain size,[12][43] which supports the hypothesis that brain-size reduction is an early response to the selective pressure for tameness and lowered reactivity that is the universal feature of animal domestication.[12] The most affected portion of the brain in domestic mammals is the limbic system, which in domestic dogs, pigs, and sheep show a 40% reduction in size compared with their wild species. This portion of the brain regulates endocrine function that influences behaviors such as aggression, wariness, and responses to environmentally induced stress, all attributes which are dramatically affected by domestication.[12][42] ” “Feral mammals such as dogs, cats, goats, donkeys, pigs, and ferrets that have lived apart from humans for generations show no sign of regaining the brain mass of their wild progenitors.[12][48] Dingos have lived apart from humans for thousands of years but still have the same brain size as that of a domestic dog.[12][49] Feral dogs that actively avoid human contact are still dependent on human waste for survival and have not reverted to the self-sustaining behaviors of their wolf ancestors.[12][50] ”

“humans have been regarded as a species so dependent on culture and technology that cultural adaptation has replaced biological adaptation. During the past 12,000 years, humans have increasingly used culture and technology—built upon agriculture and animal domestication—to control and modify the natural environment. Therefore, culture has an important role in understanding whether evolution is still influencing the biology of our species.

Adaptation, in the simplest sense, is a mechanism that allows organisms to mediate the stresses of their environment to ensure survival and reproduction. We often think that adaptation takes place through direct genetic modifications in response to environmental stress. However, many animal species are able to accommodate environmental stress simply by changing their behaviour in response to environmental conditions, without the need to resort to genetic adaptation. This could involve modifications as simple as moving to another area, changing annual or daily activities, or changing strategies for food procurement.

If behavioural flexibility cannot accommodate environmental stress, animals also have a range of physiological mechanisms that help them to respond—again, without the need for genetic adaptation. Examples include adaptive changes in heart rate, respiration and the accumulation of body fat. In combination, behavioural and physiological flexibility form a two-tiered defence against environmental stress (Fig 1). These mechanisms might be linked to the regulation of genes, but their variability might be mediated by environmental conditions without changes in gene frequency. If these defences fail or only partly buffer against environmental stress, then survivorship or repro-ductive rates might vary. In this case, changes in gene frequencies will occur over time and evolution will take place.

From the discussion above, it would be easy to conclude that humans have stopped evolving. But is this really the case? Is there any evidence that evolution is still acting on our species? Are there any conceivable circumstances in which evolution might influence our species again in the future? ” (2008 Stock)1)

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sociology/evolution.txt · Last modified: 2021/03/09 13:13 by marcos