In Fall 2007, fourteen UST first-year students participated in the biology seminar, "Evolutionary Medicine." Here, they have chosen a few ideas to share from their examination of the intersection between evolutionary biology and medicine. They have also suggested further reading and interesting web resources for those who might like to explore these topics further. The text they used was, "Why we get sick: The new science of Darwinian Medicine," by R.M. Nesse and G.C. Williams (1996) Vintage Books, New York. Pages noted below from "Nesse and Williams" refer to this text.
Evolution and Diet To help us better understand the significance and relevance of evolutionary medicine/biology on diet and the current obesity problem, there are a few concepts that you will need to know. EEA: Environment of Evolutionary Adaptedness, which is a concept used to understand how traits of organisms/species were adaptive at the time we evolved. Disease of Civilization: Illnesses that have been created or encouraged due to agriculture, mass production, and inventions. Thrifty Phenotype: This is a hypothesis that states, due to the poor nutrition or lack of nutrition in the Stone Age our genes were adapted to that diet. Supernormal Stimulus: This can be present in any of the senses. This stimulus creates a stronger response than the normal stimulus.             More than 1 out of 5 people in the United States are currently obese according to the United Health Foundation. Obesity was almost unheard of at the beginning of time, but due to the excess amount of available food and constant over-nourishment, people have become obese. That is why this is considered a disease of civilization. There are many examples that support the concept of EEA in diet. In ancient times, fats and sugars were scarce; therefore, their bodies would store them for energy reserves because it was more than likely that it would be a long time before they would be able to have them again. These fats and sugars are stored due to adaptation of our genes. This is called the thrifty phenotype. Our body only needs simple sugars found in things such as fruit, but due to supernormal stimuli of taste we crave things with the highest amount of sugar content such as chocolate or pie. This is the reason why so many people have become obese. Our diets now consist of so many fats and sugars that they build up and start to form an excess amount of fat. Since there is an excess amount of fats and sugars being consumed the bodies organs associated with digestion, detoxification, and assimilation are overworked. This constant overeating leads to higher blood pressure, and possibly heart attacks and diabetes. To prevent these diseases and excess sugar intake, artificial sweeteners have been invented, but studies have suggested they have a negative effect on the body. Artificial sweeteners are speculated to trick the body into thinking it has ingested sugar when it has not. Therefore, your blood sugar becomes deficient and this spikes your hunger, which would have the opposite effect to what was intended in using artificial sweeteners.
Further reading and interesting links: Nesse and Williams, pp 143-150 http://www.cast.uark.edu/local/icaes/conferences/wburg/posters/sboydeaton/eaton.htm
Pregnancy and Evolution Morning Sickness Adaptation is a beneficial characteristic favored by natural selection. Evolutionary biologists believe that morning sickness is an adaptive characteristic in pregnant women.  The evolutionary adaptation of morning sickness is to protect the mother and her fetus from natural toxins.  Although morning sickness is uncomfortable for many pregnant women, trying to treat it could be harmful.  Morning sickness is a common side effect during pregnancy that benefits the welfare of the fetus.  Studies indicate that a woman who has morning sickness during her pregnancy is less likely to have a miscarriage than a woman who does not.  This may be true because when the woman has morning sickness, she is ridding herself of toxins that, otherwise, could possibly harm her fetus. Evolution may also have helped us adapt by favoring genes that cause pregnant women to crave bland food.  Bland food usually carries less natural toxins than meats, spicy foods, etc., which could cause the woman to experience nausea.   Women should be careful in taking medication to prevent morning sickness.  By preventing your body from ridding itself of toxins, you could be harming your unborn child.   Parent-offspring conflict The relationship between a mother and fetus may appear to be mutual and contain shared goals due to a unity of purpose; however, mother and fetus only share half their genes, which causes a conflict in optimal fitness between the two. This is known as the parent-offspring conflict, which is a term used to signify the evolutionary conflict arising from differences in optimal fitness of parents and their offspring. Essentially, the fetus and mother want different things from the pregnancy. The mother wants the fetus to survive, and also wants to be able to have more children in the future. The fetus wants to gain the most that it can nutritionally, without knowing the effects on the mother. It is hard to believe that genes would create a competition between the mother and fetus, but doesn't evolution favor a world of survival of the "fittest"?                  The conflict in the mother's body is shown in multiple ways. The fetus secretes a substance, human placental lactogen [hPL], which ties up maternal insulin so that blood glucose levels rise and provide more glucose to the fetus. The mother counters this fetal manipulation by secreting more insulin, and this makes the fetus secrete even more hPL. This causes a medical implication, gestational diabetes, due to the manipulation of the mother's insulin levels. Also, in the early stages of pregnancy, the placental cells destroy the uterine nerves and arteriolar muscles that adjust blood flow, and this makes the mother unable to reduce the flow of blood to the placenta. If something constricts other arteries in the mother, her blood pressure will go up and still more blood will therefore go to the placenta. The placenta makes several substances that can constrict arteries throughout the mother's body, and therefore receive more of the mother's blood. This causes a medical implication as well, high blood pressure, due to the flow of most of the mother's blood to the fetus. By understanding that mother and fetus have different agendas, it is easier to understand that pregnancy may be very debilitating, as illustrated in these two examples.
Further reading and interesting links: Nesse and Williams, pp 87-90, 197-200 Morning Sickness -http://www.hkam.org.hk/temp/evolution.html Parent - Offspring Conflict - http://www.journals.uchicago.edu/doi/pdf/10.1086/382734
Antibiotic resistance Arms Race: Bacteria and viruses are in an arms race with the human defense against disease.  One side is always fighting to stay ahead of the other; both are trying to keep superiority against the other. Trade-off: This concept is based off the fact that resistant strains don't dominate in environments without antibiotics. Those strains had to give something up to get to that point. Resistance has costs. Antibiotics are naturally being made to protect organisms from their predators and competitors in nature. Mutations occur in the DNA of bacteria & viruses that limit the effectiveness of antibiotics. The battle between modern medicine and disease is an arms race.  Even when we think medicine has been found to halt disease, strains evolve much faster than we can produce an opposing force to fight off disease. The presence of antibiotics in an environment containing resistant strains may drastically change which bacterial strains are found there. When antibiotics are taken away, because resistance involves trade-offs, resistant strains lose their superiority in the environment. Antibiotics are not specific enough. For example, resistance pathogens in disease are resistant to all antibiotics of a similar chemical make-up. Further reading and interesting links: Nesse and Williams, pp 52-57. http://www.cdc.gov/drugresistance/ http://www.nyas.org/ebriefreps/main.asp?intSubsectionID=5099
Evolution of Dreaming REM sleep: a kind of sleep that occurs at intervals during the night, and is characterized by rapid eye movements, more dreaming and bodily movement, and faster pulse and breathing. We sleep every night and disregard our dreams every morning. But what if our dreams during REM sleep play a more important role in our lives than simply unconscious entertainment? Several theories exist about why REM sleep occurs, yet we have no solid answers when we ask why animals experience the same nightly adventure. The answer is evolution. We wonder why the trait of dreaming or REM sleep would be selected for. In the EEA, or environment of evolutionary adaptiveness, REM sleep must have been beneficial to a common ancestor of contemporary mammalian species. Recent studies indicate that dreaming must have evolved in our post-reptile but pre-mammal ancestors, because lizards and such don't appear to dream, but birds and mammals do. We also believe that this common ancestor was a prey species in its environment, because dreaming may have been used as rehearsals for experiences. In our ancestor's case, as prey it may have increased its survival rate when encountering predators. For students, this would lead to some implications when taking either sleeping pills or medicines that induce alertness. Sleeping pills may result in unnatural dreaming and pills such as stimulants may inhibit dreaming. If dreaming allows us to run through possible scenarios and processes information that we have learned, then sleeping pills might benefit our wellbeing and could possibly aid in memory retention whereas stimulants would inhibit these traits. Taking a sleeping pill when a person is not getting enough sleep may be beneficial whereas taking stimulants to stay awake would prevent dreaming and thus decrease memory retention and studying efficiency.
Further reading and interesting links: Nesse and Williams, pp 229-230. http://www.npi.ucla.edu/sleepresearch/rem_evolution.htm http://www.improverse.com/ed-articles/richard_wilkerson_2003_jan_evolution.htm
Aging and Evolution According to the antagonistic pleiotropy theory of aging, natural selection has favored genes that provide short-term benefits (such as increasing the probability of reproduction) to the organism at the cost of deterioration in later life. For example, a gene that deposits calcium in bones, which is advantageous earlier in life to promote healthy bones, would also result in a slow calcium deposition in arteries. The gene would still be selected for earlier in life because it improves chances of surviving youth and reproducing; genes have little concern for later life effects because an organism will have already passed its optimal reproduction period by this time. Regarding aging as an evolved condition can have many implications for medicine. If aging and death are inevitable universal constants, it could never be stopped. However, research indicates that the process by which we age could be altered, and therefore alleviate some of the conditions caused by slow deterioration. Progeria (rapid aging syndrome), food-intake restriction experiments, and the discovery of aging genes all imply that aging is not as inevitable as we are led to believe. Aging has the possibility of eventually becoming another treatable disease (but not necessarily curable). From an evolutionary standpoint, it is impossible to manually eliminate every gene that can potentially lead to future problems—but if one views senescence as a disease, then some of the biological trade-offs could be dealt with on an individual level.
Further reading and interesting links: Nesse and Williams, pp 107-122. http://longevity-science.org/Evolution.htm http://www.senescence.info/evolution.html