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Chapter 4

ANTHR101 Chapter Notes - Chapter 4: Light Skin, Sunburn, Dark Skin

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Francois Larose

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Chapter 4 Human variations and adaptations
There is genes that make for greater or lesser chances for survival and reproduction, but natural
selection results in more favourable genes becoming more frequent in a population over time.
We call this adaptation.
Adaptations are genetic changes that give their carriers a better chance to survive and
reproduce than individuals without the genetic change who live in the same environment.
How adaptive a gene or trait is depends on the specific environment, what is adaptive in one
environment may not be adaptive in another.
Genetic Adaptation: are changes within populations in response to selection pressure (over
several generations); applies only to populations.
Huas are iflueed y their eiroet through adaptatio ad aliatizatio’s.
Acclimatization Involves physiological adjustments to environmental conditions in individuals.
Acclimatization may have underlying genetic factors, but they are not themselves genetic. They
develop them during their lifetimes, rather than being born with them.
Many aliatizatio’s are simple physiological changes in the body that appear and disappear
as the environment changes. For ex: when we are cold, our bodies start to give us a
physiological response which is shivering. Also when we are in the cold a lot, our bodies increase
metabolic rates so we generate more internal heat from our bodies.
Some aliatizatio’s are closely related to genetic adaptations. For ex: Tanning, when light
skin people have been exposed to the sun for long periods of time, they tend to get darker.
Influence of the cultural environment
Humans can affect their environment.
Culture allows humans to modify their environments, and such modifications may lessen the
likelihood of genetic adaptations and physiological acclimatizatio’s. For ex: when its cold, the
effects of cold may be modified by the culture traits of living in houses, making energy to creat
heat, etc.
Culture can also influence the direction of natural selection.
Individual cultures sometimes practice behaviours that lead to physical variations between their
members and between members of one culture and another. For ex: jews share a culturally
induced physical variation (circumcision) to identify themselves as a group.
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