Why does giving mineral supplements to undernourished, anemic individuals cause many of them to die of bacterial infections? Why did Dr. Heimlich need to develop a maneuver to dislodge food from peoples’ windpipes? Why does each of your eyes have a blind spot and a significant tendency for retinal detachment, but a squid’s eyes, which provide equally sharp vision, do not have either problem? Why are depression and obesity at epidemic levels in the U.S.? When Europeans came to the Americas, why did 90% of the Native Americans die of European diseases, but few Europeans died of American diseases? Why do pregnant women get “morning sickness?” Why do people in industrialized countries have higher incidence of Crohn’s disease (related to irritable bowel syndrome) and asthma than people in undeveloped countries? Why does malaria still kill over one million people each year? Why is so much of the product, Depend® or Poise® (for incontinence), sold each year? Why do people given anti-diarrheal medication take twice as long to recover from dysentery as untreated ones? Why do people of European descent have a fairly high frequency of an allele, which, in the homozygous condition, confers resistance to HIV infection? Why do older men often develop urinary problems? Why do so many people in Austin suffer from “cedar fever?”
Charles Darwin’s theories that provided the theoretical framework for making sense out of biology have changed the world. Things ranging from the development of drug resistance, to the quirks of our species’ physiology described above, to ecological change, simply do not make sense without understanding the nonconstancy of species (the basic theory of evolution), the descent of all organisms from common ancestors (common descent), the gradualness of evolution (no saltations, no discontinuities), the multiplication of species (the origin of diversity), and lastly, Natural Selection itself.
Of course the biological issues related to evolution mentioned above are mostly related to “Evolutionary medicine,” which is a relatively recent extension of thinking in evolutionary biology in some respects. I chose (okay, cut-and-pasted) these questions to try and relate to real-world issues of biology and health.
And think about it – the best known approach to most or all of those questions is to examine how we are descended and modified from earlier progenitor species. How might our evolutionary past have shaped the diversity of our species, and our vulnerabilities, is indeed an important thing for everyone to understand.
With that, Scientific American‘s January 2009 issue is dedicated to Charles Darwin, including a series of great articles.