Darwinian

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Darwinian
Medicine

• An Evolutionary Explanation
• for Modern Disease

Clint Morehead
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Darwinian Medicine

• In 1980, evolutionary biologist Paul Ewald
  proposed an evolutionary approach to the study of
  medicine
• He suggested that we consider evolution in the
  treatment of infectious diseases

Paul Ewald
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Darwinian Medicine

• It has not been until very recently that the use
  of evolutionary theories to treat disease has
  been acknowledged.

Why?

• Religious Opposition

• Lack of General Education

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Darwinian Medicine
Branches

• Anti-viral and anti-bacterial resistance
• Real-time evolution
• Why we even suffer from disease at all
• Millions of years of hominid evolution

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Evolutionary Explanation for Disease
Question Why hasnt the Darwinian process of
natural selection eliminated the genes that make
us susceptible to diseases?
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Evolutionary Explanation for Disease
To answer this question, we must understand
hominid evolution.
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Evolutionary Explanation for Disease

• Homo sapiens and their predecessors evolved
  for millions of years as hunter-gatherers

• 10,000 years ago, they adopted agriculture

• Mismatch between design and environment

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Evolutionary Explanation for Disease
Hunter-Gatherers

• Studies of modern and ancient bands
• Fished for salmon and other fishes
• Hunted wild game
• Gathered fruits and berries
• Exercised while hunting and searching for
  shelter
• Provided nearly all essential nutrients and
  protein

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Evolutionary Explanation for Disease
Shift to Agriculture (a novel environment)

• Paleopathological studies of Dickson Indian
  mounds show that when they adopted agriculture
• 50 increase in enamel defects (malnutrition)
• Risked crop failure/starvation
• 4X increase in iron deficiency
• 3X increase in bone lesions (infectuous
  diseases)
• Life expectancy dropped from 26 to 19 years

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Evolutionary Explanation for Disease
Atherosclerosis and Cancer
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Atherosclerosis

• Second leading preventable killer among
  Americans (behind smoking)
• MetS obesity, type-II diabetes, high
  cholesterol, high blood pressure

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Atherosclerosis
Evolutionary Perspective

• Diet
• We have evolved to crave sweets and fats (today,
  these products are in abundance)
• We eat more starches and lack essential
  nutrients
• Meat comes from livestock rather than game

• Thrifty genes

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Atherosclerosis
Evolutionary Perspective

• Thrifty genes
• Because food supply was never consistent
• To regulate intake and utilization of fuel
  sources
• Efficient storage
• Today, people who exhibit this phenotype are
  those who become obese

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Cancer

• Not a novel disease
• The genome has defenses against damage (p53
  gene)
• Has spread for 2 main reasons
• Our ability to survive long after reproductive
  period
• Our tendency to interfere with our bodys biology
  (smoking, sunshine, sex, diet, physical
  inactivity)
• High levels of oxidative stress and accumulation
  of mutations over ones lifetime

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Cancer
Statistics

• 80 of all cancers occur at a post-reproductive
  age
• 25 of men over 70 have prostate cancer
• Average risk of a 25-30 year-old dying of cancer
  is 50X less than a 65-70 year-old

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Recap and Conclusion

• Many modern diseases can be understood better
  from an evolutionary perspective

• Mismatch between our design and our environment

• Knowing this could lead to more insightful
  treatments and measures of prevention

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References

• American Heart Association. Metabolic Syndrome.
  http//www.americanheart.org/ presenter.jhtml?iden
  tifier4756. A description and statistics
  regarding the metabolic syndrome.
• Diamond, Jared. The Worst Mistake in the History
  of the Human Race. Discover Magazine. May 1987.
  pp. 64-66.
• Greaves, Mel. Cancer The Evolutionary Legacy.
  Oxford Oxford University Press, 2000.
• Haffner S.M., Lehto S., Ronnemaa T., Pyorala K.,
  Laakso M. (1998). Mortality from coronary heart
  disease in subjects with type 2 diabetes and in
  nondiabetic subjects with and without prior
  myocardial infarction. N Engl J Med. 23
  339(4)229-34
• Kagawa Y, Yanagisawa Y, Hasegawa K, Suzuki H,
  Yasuda K, Kudo H, Abe M, Matsuda S, Ishikawa Y,
  Tsuchiya N, Sato A, Umetsu K, Kagawa Y. (2002)
  Single nucleotide polymorphisms of thrifty genes
  for energy metabolism evolutionary origins and
  prospects for intervention to prevent
  obesity-related diseases. Biochem Biophys Res
  Commun. Jul 12295(2)207-22.
• Onelife. http//www.onelife.com/evolve/index.html.
  A discussion of human evolution.
• Nesse, Randolf N. and George C. Williams. Why We
  Get Sick The New Science of Darwinian Medicine.
  New York Vintage, 1994.