Evolution Today

Modified: 2026-08-05 11:48 AM CDST

• Charles Darwin crystallized earlier views of evolution in 1859 with his book The Origin of Species.
  • Soon, his theory of evolution revolutionized biology and later psychology.
  • Darwin never proposed a mechanism for evolution.
  • At around the same time the Austrian monk:
• Gregor Mendel, discovered the science of genetics, another topic in this course.
  • In the early 20th century biologists linked evolution and genetics into the "Modern Synthesis" of biology.
  • Early psychologists, especially the Functionalists and later the Behaviorists linked their psychological theories to evolution as well.
  • Modern psychologists realize that all animals, including humans, are the product of a long evolutionary history.
    • That "natural history" is one aspect of evolution that we'll see in this chapter when we discuss the evolution of the brain.
    • The mechanisms of evolution will be covered somewhat when we discuss genetics.
    • All humans share 50% of their genes from each parent.
    • In the longer term, (think millions of years) all species are subject to natural selection.
• When Darwin first conceived of natural selection, he thought of it in terms of differential survival.
  • Hence, Herbert Spencer's phrase (not Darwin's) "survival of the fittest."
• Modern biology, however, has moved away from Darwin's thinking on that point.
  • Instead, biologists now talk about "reproduction of the fittest."
  • It makes sense to focus on reproduction instead of survival, because simply surviving will not ensure natural selection, whereas successful reproduction will.
  • In some cases, survival and reproduction are highly correlated, and that is probably how Darwin developed his thinking.
  • But, reproduction, not simple survival, is the key to natural selection.
  • For example, think of species that reproduce and then die.
    • Salmon and male tarantulas are two good examples.
      • Even though they die shortly after reproducing, they have fulfilled the constraints of natural selection by doing so; their genetic line continues.
    • Other good examples are genetic diseases that manifest themselves after the reproductive period of life.
    • Those diseases persist in the species even though they may be quite lethal.
    • However, their lethality occurs after reproduction.
    • Contrast that to genetic diseases that have their effect in childhood.
      • Those are much rarer because those affected rarely reproduce.
• Richard Dawkins' book,The Selfish Gene,argued that passing genes on to the next generation is the key to species continuity.
• Any living thing, he stated, could be looked at as a temporary container of genes.
  • Sociobiology makes essentially the same argument.
  • Buss' research (video) on human jealousy is a good example of how evolution alters behavior.
    • Men are much more jealous of their female partners sexual behavior where women are much more jealous of their male partners emotional behavior. Why?
      • Buss points to reproductive differences.
      • Men wish to ensure that their genes pass on to the next generation.
      • Thus, men have evolved mechanisms (courtship, for instance) to be sure that their female partner is not already pregnant by some other man.
    • Women, on the other hand, know that half of the genes of the baby she is carrying are hers.
    • But, given the 18 years that will follow the pregnancy, women want a partner who will be around for the long haul.
  • Scarily, most women who are injured or even killed by their male partners are victims of sexual jealousy.
  • Women, however, resent emotional jealousy more than sexual jealousy.
    • Imagine the following statement made by a male partner:
    • "I can talk to your friend Mary about anything, she understands me better than you every will."
    • That statement will arouse much emotional jealousy!
  • Now imagine the female partner saying:
    • "I can talk to your friend Tom about anything. He understands me better than you."
    • The male partner's reply might be, "Are you sleeping with him?"
    • If she says no, he will probably be fine.
  • Can you see the difference in the two types of jealously now?

Here are Buss's (1994) data

Buss, D. M. (1994). The evolution of desire: Strategies of human mating. New York: Basic Books.

• Finally, students may argue that evolutionists cannot agree with each other; therefore the theory itself must be faulty or wrong.
  • Those disagreements are not usually about concepts like natural selection.
  • Rather, the disagreements are about details.
  • Most modern evolutionists agree as to the central core concepts of evolution like natural selection, fitness, and evolutionary history.
    • They disagree over issues like punctuated equilibria versus gradual evolution, or about mechanisms of speciation.
  • Today, evolution is a core concept accepted by most biologists, and it gives biology a useful way of interpreting its data.

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URLs

• Enter Evolution--index, interm., long, links, graphics
  • Covers Darwin and the theory of evolution. Includes links to topics (3), scientists (25), and UC-Berkeley Museum of Paleontology. http://www.ucmp.berkeley.edu/history/evolution.html
• Links to full-text versions of Darwin's Origin of the Species and the Voyage of the Beagle

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