Human Adaptation

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Chapter 13

• Human Adaptation
• to a Changing World

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Chapter Preview

• How Have Humans Adapted Biologically to Naturally
  Occurring Environmental Stressors?
• What Is Evolutionary Medicine?
• How Are Humans Adapting in the Face of
  Globalization?

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• How Have Humans Adapted Biologically to Naturally
  Occurring Environmental Stressors?

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The Ethics of Human Biological Research

• When examining seemingly biological phenomenon
  such as disease, cultural factors must be
  considered at every levelfrom how that
  phenomenon is represented in each social group to
  how biological research is conducted.

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The Ethics of Human Biological Research The
Tuskegee Syphilis Study

• This study denied medical therapy to African
  American men in order to study supposed
  differences in the disease in this population.
• Public outcry about the study led to regulations
  that protect human subjects in biomedical
  research.

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Types of Human Adaptation

• Humans have biological mechanisms for adapting
• Genetic adaptation
• Described by Darwins theory of natural
  selection.
• Developmental adaptation
• Permanent phenotypic variation from interaction
  between genes and the environment during
  development.
• Physiological adaptation
• Short-term physiological change in response to a
  specific environmental stimulus.

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Human Growth Curve

• Franz Boas defined the features of the human
  growth curve. The graph on the left depicts
  distance, or the amount of growth attained over
  time, while the graph on the right shows the
  velocity, or rate of growth over time.

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Human Growth Curve

• Boas found that immigrant children had different
  growth curves than their genetically similar
  parents.
• This is an example of a secular trend a
  physical difference among related people from
  distinct generations that allows anthropologists
  to make inferences about environmental effects on
  growth and development.

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Acclimatization

• Long-term physiological adjustments made in
  order to attain an equilibrium with a specific
  environmental stimulus.

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High Altitude Acclimatization (above 5000 ft.)

• It takes between 2 weeks and 2 months for your
  body to adapt to living at higher altitude. Most
  of it happens without an individual even being
  aware of the changes.
• In children, lungs naturally grow larger to
  accommodate the need for increased oxygen. At
  very high altitudes, this results in a more
  "barrel chest" appearance.
• In adults, lungs may have difficulty in high
  altitudes with low oxygen and air pressure so,
  the body produces additional red blood cells to
  carry oxygen more efficiently
• You also require more water at higher altitudes.

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High Altitude Acclimatization (above 5000 ft.)
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High Altitude Acclimatization

• Observing that Kenyan runners have won most of
  the major marathon competitions over the past
  several decades, coaches have emulated the Kenyan
  approach.
• Adaptation to the hot, dry yet mountainous region
  leads to a long lean build and increased
  oxygen-carrying capacity.

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Adaptation to Heat and Cold Bergmanns Rule
From biology, it states that warm-blooded animals
from colder climates usually have larger body
masses than the equivalent animals from warmer
climates.
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Adaptation to Heat and Cold Allens Rule
Also from biology, it states that warm-blooded
animals from colder climates usually have shorter
limbs than the equivalent animals from warmer
climates.
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Human Biological Diversity For Class Discussion

• Why would the stocky body and short limbs
  characteristic of populations adapted to the cold
  of the Arctic or high altitude, as in this person
  from the Andean highlands of Peru (left)?
• Why would a tall, thin body, as seen in the
  Maasai of Kenya (right), be well adapted to the
  heat?

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The Hunting Response

• In extreme cold, the limbs need enough heat to
  prevent frostbite, but giving up heat to the
  periphery takes it away from the body core.
• Humans balance this through the hunting response
• When exposed to cold blood vessels constrict.
• Initial alternations between the open (warm) and
  shut (cold) and the temperature of the skin range
  dramatically.
• Oscillations become smaller and more rapid,
  allowing a hunter to maintain manual dexterity
  required for tying knots or sewing.

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Physiological Adaptation to Heat

• The human bodys primary physiological mechanism
  for coping with extreme heat is sweating or
  perspiring.
• Sweating is a process through which water
  released from sweat glands gives up body heat as
  the sweat evaporates.
• Without replacing sweat through drinking water,
  exposure to heat can be fatal.

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• What Is Evolutionary Medicine?

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Medical Anthropology

• A specialization that brings theoretical and
  applied approaches from cultural and biological
  anthropology to the study of human health and
  disease.
• A medical system is a patterned set of ideas and
  practices relating to illness.

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Disease and Illness

• A disease is a specific pathology a physical or
  biological abnormality.
• An illness refers to the meanings and
  elaborations given to a particular physical
  state.
• The term endemic is used to describe a disease
  that is widespread in a population.

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Visual Counterpoint For Class Discussion

• Shamans and biomedical doctors both rely upon
  manipulation of symbols to heal their patients.
  The physicians white coat is a symbol of medical
  knowledge and authority that communicates to
  patients just as clearly as does the shamans
  drum.

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Visual Counterpoint For Class Discussion

• Both shamans and medical doctors also make use of
  restricted knowledge to help their patients.
• Can you think of other ways in which cultural
  values and customs interact with disease and
  medical systems?

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Problems with Modernization

• Building the Aswan Dam in Egypt was a vital part
  of modernization for that country.
• Unfortunately, the dam increased the rates of
  schistosomiasis in the Nile River by creating a
  massive artificial lake upstream from the dam
  that provides the ideal environment for water
  snails.

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Evolutionary Medicine

• Evolutionary medicine uses the principles of
  evolutionary theory to contribute to human
  health.
• Basic to this approach is framing health issues
  in terms of the relationship between biological
  change and cultural change.

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Symptoms of Disease as Defense Mechanisms

• Evolutionary medicine proposes that many of the
  symptoms fever, vomiting, coughing, and
  diarrhea -- that biomedicine treats are
  themselves part of the bodys defense mechanism
  against infections.

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Battling Disease Culture vs. Evolution

• North American medical anthropologist Emily
  Martin has shown that scientific depictions of
  infectious disease draw upon military imagery
  common to the culture of the United States.
• An evolutionary perspective suggests that the
  quick life cycle of microorganisms makes this
  battle a losing proposition for humans.

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Evolution and Infectious Disease

• Viruses, bacteria, fungi, and parasites all have
  very short life cycles compared to humans.
• When competing on an evolutionary level, they
  will continue to pose new threats to health,
  because any new genetic variants appearing
  through a random mutation will become
  incorporated in the populations genome more
  quickly.
• While antibiotics will kill many bacteria,
  increasingly resistant strains of bacteria are
  becoming more common.

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Prions

• A prion is a protein lacking any genetic material
  that behaves as an infectious particle.
• Prions are a kind of protein that can cause the
  reorganization and destruction of other proteins
  and result in neurodegenerative disease as brain
  tissue and the nervous system are destroyed.

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Mad Cow Disease and Prions

• The beef supply of several countries in Europe
  and North America became tainted by prions
  introduced through the cultural practice of
  grinding up sheep carcasses and adding them to
  the commercial feed of beef cattle.
• Through the wide distribution of tainted feed,
  prion disease spread from sheep to cows and then
  to humans who consumed tainted beef.
• Today countries without confirmed mad cow disease
  ban the importation of beef from neighboring
  countries with documented prion disease.

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Medical Pluralism

• The presence of multiple medical systems, each
  with its own practices and beliefs in a society.
• Most individuals can reconcile different medical
  systems.
• Medical pluralism may become increasingly
  necessary in areas of public health.

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• How Are Humans Adapting in the Face of
  Globalization?

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Globalization and Human Adaptation

• The term globalization refers to the increasing
  interconnectedness of humans to one another and
  to the environment.
• Understanding globalization is critical for
  understanding human adaptation and disease.
• By examining the political ecology of disease, we
  can reveal its social causes, bringing us closer
  to finding long-lasting cures.

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Structural Violence

• Physical and/or psychological harm (including
  repression, environmental destruction, poverty,
  hunger, illness, and premature death) caused by
  exploitative and unjust social, political, and
  economic systems.
• A Health disparity is a difference in the health
  status between the wealthy elite and the poor in
  stratified societies.

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Economic Disparity

• After a natural disaster such as Hurricane
  Katrina, the ability to recover is determined by
  the relative wealth and resources available to
  the community.
• In the hard-hit Lower 9th Ward of New Orleans,
  for example, a year after water levels rose to
  above the rooflines of houses, much of the
  neighborhood is still in disarray.

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Human Population Growth

• Since the industrial revolution, human
  population size has been doubling at an alarming
  rate. The earths natural resources will not be
  able to accommodate ever-increasing human
  population if the rates of consumption seen in
  Western industrialized nations, particularly the
  United States, persist.

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Diet and Health

• The definition of malnutrition includes under
  nutrition as well as excess consumption of
  unhealthy foods. Obesity is common among poor
  working-class people in industrialized countries.
  Starvation is more common in poor countries or in
  those that have been beset by years of political
  turmoil, as evident in this emaciated North
  Korean child.

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Decline in Sperm Counts

• A documented decline in human male sperm counts
  worldwide may be related to widespread exposure
  to hormone-disrupting chemicals.

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Health Education

• These Gambian children are spending their
  Saturday in the school library to make up skits
  and songs about health issues that they will take
  out into their local community.
• They are a part of a peer health educator group,
  a tradition that stretches throughout The Gambia
  and beyond.