biological diversity and culture

7/31/2019 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)



- 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.



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.



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.



IQ scores does not measure innate intelligence rather, they test with the

preference to middle- class standard, phenotypical intelligence

biological diversity and culture

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