NOTES for WEEK 4

TEXT Ch 4 GENES, CULTURE, and ADAPTATION

I. ADAPTATION pp 74-78

These lecture notes are intended to assist you in self-study. You can look at adaptation at several levels. A scheme is proposed on page 74; here is a slight modification that applies here and to other units in the book.

• Genetic change at the population level. These are changes in gene frequencies wrought by 'population genetics' which include:

1. Natural selection

2. Random genetic drift

3. Mutation

4. Gene flow

In time, change can be so great that an entirely new species emerges.

• Developmental changes during growth and maturation. These changes are irreversible.
• Physiological changes that are reversible. These can be rapid, as in the eye accommodating to light, or longer term as in tanning of the skin.
• Cultural and individual changes are about how we cope. Ice Age hunters of the Upper Paleolithic survived arctic conditions by use of their wits, skill, and ingenuity.

The authors on pp 74-75 refer to the 'Red Queen' idea in biology. At its core is an idea you understand very well with your own finances: you seem to run faster and faster just to stay even.

In the 'arms race' during the Cold War, each side produced more and more weapons just to stay even. Antibiotics manufacturers do it in the racer to beat mutating drug resistant bacteria. In the animal world it can reach a runaway pace. You see it in birds such as peacocks whose males have developed flamboyant and biologically 'expensive' displays to be successful in sexual competition.

On page 76 is an illustration of one of the old and venerable rules in physical anthropology: Allen's rule (also discussed in section IV, unit 4.2). A long limbed, linear body is best suited for the tropics where heat loss is important. A stocky, short limbed body is best suited for the arctic where heat retention is crucial.

II. ADAPTATION IN BIOLOGICAL EVOLUTION; MALARIA pp 78-91

SKIP the section pp 78-80 on genetic codes. Aren't you glad?

READ pp 80-84. All of this is an introduction to the PROFILE (pp 84-91).

READ the PROFILE about Malaria and Agriculture. It is a major unit, important in its own right, and is a guaranteed exam question. While you are reading, keep these facts in mind:

• Two-hundred fifty million people suffer from malaria worldwide.
• It is caused by a protozoan parasite Plasmodium. It requires both the insect and a person to complete its life cycle.
• It is transmitted by the Anopheles mosquito.
• In people, the Plasmodium invades and destroys red blood cells.
• Entry into tropical forests, aided by iron tools 2000 years ago exposed people to mosquitoes and malaria.

****Malaria is an infectious disease -but- ****Sickle Cell Anemia is a genetic disease.

• Our genes are in pairs. For each pair we get one from Mom and one from Dad.
• Sickle Cell Anemia is controlled by a single gene, itself based on a single point mutation at the molecular level. It's historic origin in unknown.

-therefore-

• •IF neither inherited gene is sickle cell, THEN there is no sickle cell anemia.
• •IF one inherited gene is sickle cell, THEN a person has the Sickle Cell Trait. This is advantageous in a malarial environment.
• •IF both genes are sickle cell (both parents have to be carriers), THEN the person has Sickle Cell Anemia

-sickle cell anemia and malaria go together . . . -

• In people with NO sickle cell anemia, the body removes red blood cells after 120 days of service.
• In people with the sickle cell trait, the red blood cells are removed after 90 days.

-the trait is advantageous . . . -

• The plasmodium requires 100 days to live out its time in red blood cells. They can do it in normal people, but in folks with the sickle cell trait, the red blood cells are taken out of service after 90 days-which destroys the plasmodium, too.
• Sickle Cell Anemia is a painful, debilitating disease. If a suitable donor is available, a cure is possible with chemotherapy and a marrow transplant.

There is a section on Malaria in the READER which we will treat separately. In the TEXT, read about the foods that help resist malaria on p 91.

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III. DEVELOPMENTAL, PHYSIOLOGICAL, HIGH ALTITUDE, & CULTURAL ADAPTATION pp 91-102.

This is straightforward reading. Underline and highlight as you go along. The section on the Samoans illustrates a theme often encountered with Pacific Islanders and Native American Indians: modern diets and inactivity have brought health problems like obesity, adult onset diabetes, and cardiovascular disease.

IV. DIRECT MEDICAL CONTROL STRATEGIES, COPING, PROFILE on SICKLE CELL ANEMIA, MALADAPTIVE PATTERNS pp 102-117

p 102 -Pay attention to ethnomedical systems which are the beliefs and practices of healers and patients-whether they are shamans or your own MD medical doctor.

-Cosmopolitan Medicine is simply another term for allopathic Western biomedicine.

p 103 -Humoral, hot/cold, wet/dry should be familiar to you.

p 104 -You'll see mention of plant and animal products used in healing. We have units on this elsewhere; they aren't adequately covered in the TEXT.

p 104 -Even Western medicine has its dark side. 'Doctor-caused' diseases are called 'iatrogenic' diseases. Many years ago 'des' was prescribed for infertility. It caused reproductive system cancers in the next generation. Thalidomide, a European tranquilizer caused phocomelia-which was a failure of limbs to form.

pp104-117 -Read all of this except female circumcision which we cover later in our unit on the health of women.

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V. OTHER INFECTIOUS DISEASES/GENETIC DISEASES THAT HAVE AN EVOLUTIONARY RELATIONSHIP (not in text)

CYSTIC FIBROSIS

Cystic fibrosis (CF), is a lethal genetic disease in the white population. It is rare in Orientals. It is a disease of the lungs and pancreas. It seems to have originated long ago; it is believed to be at least 52,000 years old. The latest findings suggest that, while it is lethal in the homozygous condition, it may give survival advantages to those who carry a single copy of the gene, the heterozygous condition. The single sickle cell allele provides a selective advantage in a malaria-ridden environment. What is the advantage conferred by the cystic fibrosis allele?

The cystic fibrosis allele may have survived through hundreds of human generations because it gives protection against cholera. About one in every twenty Caucasians carries the cystic fibrosis gene. Cholera kills by causing a severe and unrelenting loss of fluid. Most of the disease victims die of dehydration. The CF gene in the homozygous condition protects carriers against cholera because it blocks the same molecular pathway used by the cholera disease toxin to cause diarrhea. These findings would also suggest a greater antiquity for cholera than that recorded in historic times.

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TAY-SACHS DISEASE

This lethal genetic disease is characterized by a very early onset, progressive retardation in development, paralysis, dementia, blindness and death by age three or four. This recessive disorder is most common in certain families of Eastern European Jewish origin. It is caused by a deficiency of a specific enzyme, hexosaminidase. Tay-Sachs, therefore is a completely incurable, disease programmed in the genes when inherited from both parents (homozygous).

Study has shown, however, that in the heterozygous form that (like sickle cell and CF) it conveys a selective advantage. That advantage is an increased resistance to tuberculosis, a disease common in the Jewish ghettos of Europe.

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Resources

"Cystic Fibrosis gene at least 52,000 years old" Chicago Tribune June 1, 1994.

"Cystic Fibrosis gene a protector" Chicago Tribune October 7, 1994.

Diamond, J. "Curse and Blessing of the Ghetto" Discover. March, 1991 pp 60-65.

"Malaria: A Case Study of Coevolution" Scientific American. January, 1992 p 127.

Naik, G. "Turning Mosquitoes Into Malaria Fighters" Wall Street Journal. June 19, 1997.

Taubes, G. "Malarial Dreams" Discover. March, 1998 pp 108-116.

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READER Endemic Malaria in Sardinia pp 79-90.

This reading is a case study of malaria in Sardinia, an island region that is part of Italy. Read this article for the broad ideas. You are not responsible for specific details, but I may ask something about the article as a clue that you have read it.

Malaria was once widespread in continental Europe and here in the United States. Improvement in living conditions and eradication efforts with the now banned insecticide DDT effectively eliminated the disease here

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READER Genital Herpes pp 315-321. There is an error in the syllabus; it erroneously says pp 313-315.

I hope you will read this article. Due to the error in the syllabus, however, you are not responsible for the article on the exam.

As I read this article, I was reminded of an incident in the news a few years ago. A teenage woman was raped on an elevated train station. She contracted genital herpes from her attacker.

With her parent's approval she went public and mounted a campaign for victim's rights. She was very articulate in telling about her grief of being stuck with this miserable disease.

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READER AIDS as Human Suffering pp 333-341.

I've included this section because this disease and others have a human dimension.

The Wall Street Journal ran a poignant article many months ago written by one of its own reporters, David Sanford (WSJ November 6, 1998).

He reported living with his partner of 28 years who is HIV-negative. Sanford reports that he is certain that he acquired AIDS in a Manhattan bathhouse in a sexual encounter with a man whose name he didn't catch. He was diagnosed with AIDS in the days when AIDS was still called GRID.

A week after the encounter, he had flu-like symptoms-aches and respiratory illness along with high fever and a rash. In a couple of years he would tire easily, had night sweats, and weight loss. A blood test confirmed his infection in 1989.

By 1991, Sanford's T cell count (an important indicator for AIDS progression). He wrote his obituary and made preparations to die. When his mother died and left him $180,000. He blew the whole thing on expensive restaurants and foreign travel . . .live well because soon I die!.

But then in 1995 he began therapy with the protease inhibitors. Sanford began to gain weight. His T cell count recovered and he continued working for Dow Jones, the publisher of the Wall Street Journal.

He noticed a new trend in the specialist's office he visited in New York: the clientele all looked happier and healthier. The drugs were giving all of them a new lease on life.

Sanford said in the article that he felt guilty because he was getting the best possible medical care-and all of it was paid by his company insurance. Such care is unavailable to most of the world's AIDS sufferers and the uninsured in this country.

..... CJ'99