biological diversity and culture
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Biological Diversity and Culture
Explaining Human Biological Diversity
Although the problems involved in categorizing human beings according to
race are immense, it is obvious that biological differences exist among people.
Before considering some explanations for human biological diversity, a reminder
is in order: hominid evolution has involved an increasing reliance in cultural
means of adaptation. Because it involves cultural means, our adaptive apparatus
is much more flexible than that of any other animal. Adaptation is not totally
biological; many contemporary humans live in environments for which their
biological attributes are not particularly suited. However, they survive because of
dealing with the environment.
Researchers have established links between biological traits whose genetic
determinants are known (such as blood groups) and forces of natural selection
(such as disease). However many human biological traits are not subject to simple
genetic control.
Lactose Tolerance
One of the many aspects of human biology to which both genetic and
environmental factors contribute.
Genes and environment also seem to work together to produce a
biochemical differences between human groups: the ability to digest large
amount of milk.
Milk - contains complex sugar called lactose. Its digestion depends on the enzyme
called lactase and works in the small intestine. Lactase production ceases
after weaning among all the mammals except humans of their pets.
90% of Northern Europeans and their descendants
- is lactose-tolerant, they can digest milk with no difficulty
80% of 2 African Populations (Tutsi of Uganda & Fulani of Nigeria)
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- produce and digest milk easily
Nonherding populations ( Yoruba & Ibo in Nigeria, Ganda in Uganda, Japanese,
and other Asians, Israelis, Eskimos, and South American Indians)
- they cannot digest lactose
Variable human ability to digest milk seems to be a difference of degree
rather than of kind. Some populations can tolerate very little or no milk, whereas
others are able to metabolize considerably greater quantities. Studies showing
that people who move from low-milk or no-milk to high-milk diets increase their
lactose tolerance suggest an environmental component.
Skin Color
- an another complex biological trait
- several genes interact with environmental conditions to produce variation
in skin color among human
Melanin - a chemical substance manufactured in specialized cells in the lower
layers of the epidermis, or outer skin layer
Melanin cells of darker-skinned people produce more and larger granules
of melanin than those of lighter-skinned people.
Epidermal Melanin - regulates absorption of ultraviolet radiation from the sun
- protects people against variety of maladies, including
sunburn and skin cancer
Before 16th
Century - dark-skinned people lived in the tropics
People who lived in the tropics are dark-skinned while those who liveoutside the tropics have lighter skin. A gradual transition from dark brown to
medium brown happens when one leave the tropics.
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Darkest population of Africa
- evolved not only in the equatorial forest but in savanna, or open
grassland country
Disadvantage of lighter-skinned people
- in the tropics with intense ultraviolet radiation from the sun, unprotected
human face the threat of severe sunburn, which can increase susceptibility
to disease
Sunburn
- impairs the body’s ability to sweat, thus light skin-color, given tropical
heat can diminish human ability to live and work in equatorial climates
Cancer
- can be produce in long-term exposure to high levels of ultraviolet
radiation
- usually occurs after the reproductive period has ended
W. F. Loomis ( 1967)
- explained both light and dark skin color in terms of selective
forces- the role of ultraviolet radiation in stimulating the manufacture of vit. D by the human body. The unclothed body can synthesize vit. D directly
from the sunlight, but in an over- cast environment that is also cold enough
to clothed themselves during most of the year, apparel impedes the
manufacture of vit. D.
Vitamin D
- a shortage of this interferes with the absorption of calcium in the
intestines and a nutritional disease known as rickets may develop.
Rickets
- interferes with the absorption of calcium and causes softening and
deformation of the bones; in women, this deformation can interfere
with childbirth.
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Northern Areas
- dark skin can come under selective control because heavier
concentrations of melanin in the screen out more ultraviolet radiation.
Loomis
- suggested that in the tropics, dark skin color protects the body against
an overproduction of vitamin D by screening out ultraviolet radiation.
Ultraviolet radiation
- in northern climates it is intense during the summer months.
Light- skinned people adapt to this environmental stress both culturally-- bywearing clothes and wearing lotions—physiologically- by tanning.
Often, populations in geographical distant parts of the world share certain
biological traits.
Human biology is not the immutable phenomenon assumed by the classifiers of
race. Instead, it is inherently plastic, changing constantly even without
genetic change.
Race and Intelligence
- over the centuries groups with power have attempted to justify their
privileged and dominant social positions by declaring minorities to be
innately inferior.
- belief in biologically based inferiority of Native Americans has been
argument for their slaughter confinement and neglect.
Jensenism ( Arthur Jensen)
- is the belief that genes determine intelligence.
- this asserts that blacks are hereditarily incapable of performing as well as
whites do.