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The Legacy of Charles Darwin

Tim M. Berra

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Darwin’s concept of evolution forever changed the way we understand how our natural world works. In this article, we learn about:

  • Darwin’s observations of nature that led to his ideas
  • Why evolution via natural selection is the basis of all of biology
  • How Darwin’s ideas affected our understanding of the sciences
  • How evolution continues to affect us today

February 2009


Charles Darwin in his later years. The year 2009 marks his 200th birthday.
Source: Wikimedia Commons. Photo by J. Cameron, 1869. Original source: Harvard University publications.

The book Origin of Species is 150 years old in 2009.

Charles Darwin (1809-1882) was an extraordinary man by any standard. The theory of evolution by natural selection as elaborated in his book, On the Origin of Species,1 is considered by historians and philosophers of science to be one of the most important ideas that the human mind has ever produced.2 The implications of his very useful insight extended beyond science and profoundly impacted the human mind.

Darwin’s big ideas

Darwin spent 5 years on the HMS Beagle, exploring the world.

Darwin was born and educated at a time when special creation was the prevailing scientific view. That is, God created the universe and all species a few thousand years ago, and they were unchangeable. “Revelation”—not research—provided this view. Darwin began the HMS Beagle voyage (1831-1836) with this belief. Observations made during the voyage—a surveying trip around the world, which included a stop in the Galapagos Islands—made Darwin question the creation myth and immutability of species. He found marine fossils thousands of feet above sea level, and he reasoned that the land had been elevated by earth movements; it had not been inundated in a great biblical flood. Other observations that influenced his thought included:

Darwin found marine fossils way above sea level.
  • The fossil mammals he uncovered in South America resembled living mammals from the same area. Why should this be if each species were specially created? Extinction was hardly recognized in those days.

  • Why did the animals on islands off continental areas resemble those of the nearest land mass if each species were created in place?

  • Why were there so many species in an island group that looked very similar but with slight differences from island to island? It is as if “one species had been taken and modified for different ends,” he wrote in Voyage of the Beagle.3

None of these things made sense from a creationist perspective. In 1844, he wrote to his botanist friend, Joseph Dalton Hooker (1817-1911) “I am almost convinced (quite contrary to the opinion I started with) that species are not (it is like confessing a murder) immutable.”

The elegant simplicity of Darwin’s reasoning can be distilled as follows:

  • There is variation in nature—many more offspring are generated than can survive; therefore, there is a struggle for life in which favorable variations are preserved and unfavorable variations are removed. This leads to evolution, which he defined as “descent with modification” and to the formation of new species.
Natural selection was Darwin’s biggest idea.
  • Nature is doing the selecting for the forms best adapted to a particular environment, so he called the process natural selection—as opposed to artificial selection that breeders impose. We now know that mutation, chromosomal rearrangements, sexual reproduction, and so on, are the sources of genetic variation, but Darwin had no knowledge of such topics. Today we can speak of “descent with modification” as “a change in gene frequency,” and natural selection is simply “differential reproduction,” that is, one genetic variant leaves more offspring than another.4

  • Darwin borrowed the expression “survival of the fittest” from economist Herbert Spencer (1820-1903). Evolutionary fitness means reproductive fitness. In modern terms, the fittest is the one who gets the most genes into the next generation—not necessarily the biggest or strongest individual.

Evolution via natural selection is the basis of all of biology.

Darwin’s explanation of evolution via natural selection is the basis of all of biology and its applied sub-disciplines of medicine, agriculture, and biotechnology. No other biologist in the history of our species has had an impact of this magnitude. In the words of the eminent geneticist Theodosius Dobzhansky, “Nothing in biology makes sense except in the light of evolution.”5 The paradigm shift from creation to evolution has moved intellectual endeavors from an untestable beliefs to a rational understanding that flows from the scientific method. This, in turn, has allowed a vast array of advances in knowledge.

Darwinian implications

One of the attributes of a powerful scientific theory is that it enables future research and understanding. For example:

Disease prevention depends on an understanding of evolution.
  • Darwinian or evolutionary medicine6 explains how some disease symptoms, such as fever, may be a response favored by natural selection as a defense against pathogens. Some genetic diseases such as sickle cell anemia may allow differential survival of its victims in malarial zones—a phenomenon called a balanced polymorphism (genetic variation, e.g., blood types).4 This results in a deleterious gene (sickle cell) being maintained at a relatively high frequency in a population, even though it can be lethal in a double dose (homozygous), because it protects its carriers against malaria when present in a single dose (heterozygous).

  • Evolutionary thinking explains the arms race waged by pathogens and hosts that prevents either from being eliminated completely. Darwinian reasoning easily explains the development of antibiotic-resistant bacteria through the flagrant overuse of antibiotics. A drug kills the susceptible bacteria leaving bacteria with a pre-existing resistant mutation to build up the next generation. Then when you actually need the antibiotic for a bacterial infection, patients and doctors find that the drug is ineffective. This is evolution, pure and simple.

Species management has evolutionary consequences.
  • A similar process occurs in agriculture with the overapplication of pesticides, and the formation of pesticide resistant pathogens, insects, and noxious plants. Australians are very familiar with the myxomatosis versus rabbit “arms race,” whereby the virus initially killed 99% of the non-native rabbits. The virus that causes myxomatosis was introduced deliberately in Australia in 1950, in an attempt to control exotic rabbit infestation. Given enough time, however, the surviving rabbits returned in force as the virus evolved in the direction of less virulence, and the rabbits were selected for more resistance to the virus.7
Kin selection has an evolutionary context.
  • Evolutionary psychology and evolutionary ethics help explain the origin of morality.8,9 Peacemaking among non-human primates by the calming effect of mutual grooming to diffuse aggression may be seen as the precursor of what became morality in humans.10 Modern religions are recent human inventions—a mere few thousand years old. The antecedents of morality, on the other hand, clearly evolved before humanity, as reflected in the empathy exhibited by bonobos (Pan paniscus), and the reciprocity of chimpanzees (P. troglodytes).11 Kin selection, whereby an individual sacrifices for a close genetic relative, makes sense in an evolutionary context because some of the same genes of the individual making the sacrifice will be passed on by the kin who survives. This is referred to as inclusive fitness.12

  • The ancestry of the AIDS virus, HIV-1 (human immunodeficiency virus-1) has been traced to SIVcpz (simian immunodeficiency virus) carried by our closest living relative, the chimpanzees.13 This is not surprising from an evolutionary perspective. Somewhere in a high school today, there is a student whose future career may contribute to the control of the AIDS epidemic. What chance of that would there be if creationism were taught as science in high school?

Biotechnology uses Darwin’s ideas.
  • Biotechnology—whether in the form of genetically modified crops, designer drugs, gene therapy, or the human genome project—all derive from Darwin’s profound insight. Darwin had no knowledge of genes or chromosomes, or of how inheritance worked. This required additional input from the understanding of Gregor Mendel’s (1822-1884) genetic work.
Darwin’s ideas led to DNA research.
  • The modern evolutionary synthesis grew from Darwin’s explanation of natural selection and Mendel’s demonstration of inheritance augmented by the research of mathematically oriented population geneticists. This fusion of knowledge moved evolutionary science forward to the middle of the 20th century.14 James D. Watson’s and Francis Crick’s 1953 demonstration that the molecular structure of DNA allowed for genetic coding was a huge breakthrough that ultimately made it possible to sequence the three billion chemical base pairs that compose the human genome and identify the approximately 20,000-25,000 genes in human DNA.15,16

  • Recent discoveries in evolutionary developmental biology, known as evo-devo, have shown that very similar genes are present in very dissimilar animals. These body-shaping genes are controlled by DNA switches called enhancers that turn them on or off at various times in development. Such enhancers are a major factor in the evolution of anatomy.17

Evidence is always subject to empirical testing.
  • TV viewers are familiar with DNA [deoxyribonucleic acid] analysis popularized on CSI [Crime Scene Investigation] programs. DNA-sequencing techniques—whereby the arrangement of A-T-C-G of genetic codes are compared—can convict or exonerate people accused of crimes. Similar techniques can confirm or deny paternity in disputed cases, or can ensure that the expensive grouper fillets you purchase are not flesh from lesser species. Such evolutionary tests are accepted by the judicial system because they pass the Daubert standard for scientific evidence; that is, the techniques were subject to empirical testing, published in peer-reviewed journals, and accepted by the scientific community.18 No such creationist tests exist; if they did, they could not meet scientific or judicial standards.

The Paradigm Shift

Darwin changed the course of scientific thinking.

The above examples are just a sample of the benefits to society that flow directly from the creative power of Charles Darwin’s theory of evolution by means of natural selection (for more about Darwin’s legacy, refer to Charles Darwin: The concise story of an extraordinary man19). The publication of On the Origin of Species, on 24 November 1859, precipitated one of those rare events in the history of science—a paradigm shift. Philosopher Thomas Kuhn used this term to refer to the replacement of one world view by another.20 Examples of a paradigm shift in science include the replacement of the earth-centered Ptolemaic system by the sun-centered Copernican system; and the replacement of Newtonian physics by relativity and quantum physics. The paradigm shift instigated by Darwin’s legacy has made obvious the superiority of this scientific method as a means of understanding the world around us.

Tim M. Berra, Ph.D., is Professor Emeritus in the Department of Evolution, Ecology, and Organismal Biology at Ohio State University in Mansfield. He is a two-time Fulbright Fellowship recipient, and he is the author of over 75 scientific papers and six books, including Charles Darwin: The Concise Story of an Extraordinary Man, that tells the story of Darwin’s life and his significance to Western thought. The book was published by Johns Hopkins University Press for the celebration in 2009 of the 200th anniversary of Darwin’s birth and the 150th anniversary of the publication of On the Origin of Species. Dr. Berra received his Ph.D. in biology from Tulane University in 1969.
http://www.mansfield.ohio-state.edu/faculty/tberra/index.htm

The Legacy of Charles Darwin

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Understanding Evolution

Your one-stop source for information on evolution. Learn the facts in Evolution 101, browse the resource library, read about evolution in the news, or discover a wealth of materials to help educate others about evolution and related concepts—it’s all right here! http://evolution.berkeley.edu

The HMS Beagle Voyage

See maps and text about this historical event; this includes a timeline of Darwin’s journey and research data.
http://www.aboutdarwin.com/voyage/voyage01.html

Read Darwin Online

See links to online copies of all editions of Charles Darwin’s literature.
http://darwin-online.org.uk/

About Charles Darwin

http://www.amnh.org/exhibitions/darwin/ (exhibit)
http://www.pbs.org/wgbh/evolution/library/11/2/quicktime/e_s_2.html (video)

15 Evolutionary Gems

Review this pdf file of an article in Nature magazine, January 2009, provided for the public, scientists, and educators as a resource for evidence of evolution by natural selection.
http://www.nature.com/nature/newspdf/evolutiongems.pdf

Natural Selection

Read the interview with Douglas Futuyma “Natural Selection: How Evolution Works” on ActionBioscience.org. The second link takes you to Richard Lenski’s article “Evolution: Fact and Theory.”
http://www.actionbioscience.org/evolution/futuyma.html
http://www.actionbioscience.org/evolution/lenski.html

Understanding Evolution

A cornucopia of easy-to-read explanations of every aspect of the theory of evolution.
http://evolution.berkeley.edu/

Panda’s Thumb

The Panda’s Thumb is the “virtual pub” where “patrons gather to discuss evolutionary theory, critique the claims of the antievolution movement, defend the integrity of science and science education in America and around the world, and share good conversation.”
http://www.pandasthumb.org

Darwin’s Galapagos

The Charles Darwin Foundation publishes a regularly updated online repository of all known species from the Galapagos Islands. Making this information publicly available represents an important milestone towards a better, comprehensive understanding of the unique Galapagos biodiversity.
http://www.darwinfoundation.org/english/pages/index.php

For Educators: Evolution Activities

The first link takes you to the PBS evolution series, which first aired in September 2001, has a superb website of teaching resources for evolution. The second link is for the rich activities created for the web site Understanding Evolution. The third takes you to ENSI’s resources. http://www.pbs.org/wgbh/evolution/
http://evolution.berkeley.edu/evosite/evohome.html
http://www.indiana.edu/~ensiweb/

  1. Darwin, C. 1859. On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. John Murray: London.
  2. Dennett, D. C. 1995. Darwin’s dangerous idea. Touchstone: New York.
  3. Darwin, C. 1839. Voyages of the Adventure and Beagle, Volume III –, Journal and remarks. 1832–1836. London: Henry Colburn (The Voyage of the Beagle).
  4. Berra, T. M. 1990. Evolution and the myth of creationism. Stanford University Press: Stanford
  5. Dobzhansky, T. 1973. Nothing in biology makes sense except in the light of evolution. American Biology Teacher 35: 125–129.
  6. Nesse, R.M., and Williams, G.C. 1996. Why we get sick. Vantage Books: New York.
  7. Berra, T. 1998. A natural history of Australia. University of New South Wales press/Academic Press: Sydney/San Diego.
  8. Barkow, J. H., Cosmides, L., and Tooby, J. (eds). 1992. The adapted mind. Oxford University Press: Oxford.
  9. Wright, R. 1994. The moral animal. Pantheon Books: New York.
  10. de Waal, F. 1989. Peacemaking among primates. Harvard University Press: Cambridge.
  11. de Waal, F. 2005. Our inner ape. Riverhead Books: New York.
  12. Hamilton, W. D. 1972. Altruism and related phenomena, mainly in the social insects. Annual Review of Ecology and Systematics 3: 193–232.
  13. Bailes, E., et al. 2003. Hybrid origin of SIV in chimpanzees. Science 300: 1713.
  14. Larson, E. J. 2004. Evolution: the remarkable history of a scientific theory. The Modern Library: New York.
  15. Lander, E.S., and 19 coauthors. 2001. Initial sequencing and analysis of the Human genome. Nature 409: 860–921.
  16. Venter, J. C., and 273 coauthors. 2001. The sequence of the human genome. Science 291: 1304–1351.
  17. Carroll, S. B. 2005. Endless forms most beautiful: the new science of evo devo and the making of the animal kingdom. W.W. Norton: New York.
  18. Mindell, D. P. 2009. Evolution in the everyday world. Scientific American 300: 82–88.
  19. Berra, T. M. 2009. Charles Darwin: The concise story of an extraordinary man. Johns Hopkins University Press, Baltimore.
  20. Kuhn, T. S. 1962. The structure of scientific revolutions. University of Chicago Press: Chicago.

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