Is Evolution Making Us Less Intelligent?

A Stanford University biology professor, writing in a peer-reviewed journal, suggests neo-Darwinian evolution is causing humankind to lose mental capacity—at least for the last 3,000 years. This conclusion may suggest that the second law of thermodynamics applies to biological systems and provide important support for a creation model.

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Are humans becoming smarter or more stupid? Comparing our modern lives and technology with that of any preceding generation, one might think we are becoming increasingly smarter. But, in two papers published in Trends in Genetics, Gerald R. Crabtree of Stanford University claims that we are losing mental capacity and have been doing so for 2,000–6,000 years! The reason, Crabtree concludes, is due to genetic mutations—which are the backbone of neo-Darwinian evolution.

Human brain in x-ray viewThe significance of these articles is that a senior scientist, writing in a peer-reviewed journal, claims that humankind is susceptible “as a species to random genetic events [mutations] that reduce our intellectual and emotional fitness.”1 This conclusion is consistent with the second law of thermodynamics, which states (among other things) that natural systems tend toward a state of disorder and that random processes cannot bring order out of disorder. (This is such a fundamental law of nature that British astrophysicist Arthur Eddington wrote, “But if your theory is found to be against the second law of thermodynamics I can give you no hope; there is nothing for it but to collapse in deepest humiliation.”2)

In contrast, the theory of neo-Darwinian evolution claims that natural systems progress in the opposite direction. That is, random genetic mutations serve to advance a species toward a state of order. Yet Crabtree’s findings seem to imply that the second law of thermodynamics is right, and neo-Darwinian evolution is wrong.

Based on data produced by the 1000 Genomes Project Consortium3 and two recent papers in Nature,4 Crabtree estimates in the first article that, in the past 3,000 years (approximately 120 generations), about 5,000 new mutations have occurred in the genes governing our intellectual ability. He claims most of these mutations will have no effect, while about 2–5 percent are deleterious and “a vanishingly small fraction will increase fitness.”5 Crabtree bases his conclusion that humankind is losing mental capacity on the ratio between the deleterious and the beneficial mutations. (One critic calls this a “back-of-the-envelope calculation;”6 but if Crabtree’s objective is a reasonable order-of-magnitude estimate, then he seems to have achieved that.)

In the second article, Crabtree moves away from the science of genetics and moves into anthropology, which he admits is “not [his] area of expertise.”7 He opines that humanity began losing intellectual abilities with the advent of agriculture and permanent communities 3,000 years ago because such a change would “tend to reduce the selective pressure placed on every individual, every day of their life.”8 In the 50,000–500,000 years prior, Crabtree suggests, humankind achieved an increase in intellectual abilities as they experienced an “expansion of the human frontal cortex and endocranial volume”:9

Thus, to understand how 2000–5000 genes [which govern intellectual function] were optimized for abstract thought, we almost certainly have to look to this period 50 000–500 000 years ago and to ancestors common to all humans today. Somehow the selective pressures on these ancestors led to the evolution of a brain capable of writing symphonies and performing higher mathematics [emphasis added].10

He concludes humans improved in intellectual capacity for 50,000–500,000 years, “perhaps reached a peak 2000-6000 years ago,”11 and then began to decline.

It is important to understand that Crabtree’s research is presented in two separate articles written from two very different points of view. Part 1, about humankind’s declining intellect, is based on the science of genetics; part 2, about the 50,000–500,000 years of improvement, is based on anthropology. He may have written two articles instead of one due to the fundamental shift from scientific data in part 1 to speculation in part 2. Genetics explains the decline, but it cannot explain the years of improvement; these happened “somehow.” Since hard science cannot explain it, it might be considered a miracle; but Crabtree conjectures:

Thus, extraordinary natural selection was necessary to optimize and maintain such a large set of intelligence genes. This optimization probably occurred in a world where every individual was exposed to nature’s raw selective mechanisms on a daily basis.12

Primitive humans lived in a dangerous world, and only the fittest survived. This sounds plausible—except when considered in the context of the genetic data. If humans developed 5,000 mutations in the past 3,000 years, then we can estimate that 83,333–833,333 mutations developed in the earlier 50,000–500,000 years. The 2–5 percent deleterious mutations failed to survive, and the “vanishingly small fraction” of beneficial mutations were presumably the basis for our intellectual growth. But what is a “vanishingly small fraction” numerically? It must be at least a factor of 100 lower than the harmful 2–5 percent or it would be measurable. Thus, taking 0.05 percent as a rough approximation, there were at most 42–417 new beneficial mutations in 50,000–500,000 years. If “vanishingly small” is an accurate description, then the actual number is probably even less.

Is it plausible to imagine that so few beneficial mutations could evolve “a brain capable of writing symphonies and performing higher mathematics”? It seems unlikely. Perhaps this is why Crabtree does not offer any calculations in part 2 similar to what we have done above. Instead, he relies on the “extraordinary natural selection,” implying there was a beneficial mutation rate much greater than presently observed. However, to be scientific, one must have a plausible hypothesis to explain this—yet none is proposed.

In conclusion, these two articles in Trends in Genetics seem to support the second law of thermodynamics while undercutting Darwinian evolution. They might even be said to promote a creation model!

References:

  1. Gerald R. Crabtree, “Our Fragile Intellect, Part 1,” Trends in Genetics 29 (January 2013): 1.
  2. Arthur S. Eddington, The Nature of the Physical World (Cambridge, UK: Cambridge University Press, 1928), 74.
  3. 1000 Genomes Project Consortium, “A Map of Human Genome Variation from Population-Scale Sequencing,” Nature 467 (October 28, 2010): 1061–73.
  4. J. Kenneth Baillie et al., “Somatic Retrotransposition Alters the Genetic Landscape of the Human Brain,” Nature 479 (November 24, 2011): 534–37; Augustine Kong et al., “Rate of de novo Mutations and the Importance of Father’s Age to Disease Risk,” Nature 488 (August 23, 2012): 471–75.
  5. Crabtree, “Our Fragile Intellect, Part 1,” 2.
  6. K. J. Mitchell, “Genetic Entropy and the Human Intellect,” Trends in Genetics 29 (February 2013): 59.
  7. Crabtree, “Our Fragile Intellect, Part 2,” Trends in Genetics 29 (January 2013): 3.
  8. Crabtree, “Our Fragile Intellect, Part 2,” 4.
  9. Ibid.: 3; Richard G. Klein, The Human Career: Human Biological and Cultural Origins, 2nd ed. (Chicago: University of Chicago Press, 1999); Leslie C. Aiello and R. I. M. Dunbar, “Neocortex Size, Group Size and the Evolution of Language,” Current Anthropology 34 (April 1993): 184–93.
  10. Crabtree, “Our Fragile Intellect, Part 2,” 3.
  11. Crabtree, “Our Fragile Intellect, Part 1,” 2.
  12. Crabtree, “Our Fragile Intellect, Part 2,” 3–4.

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By Dr. Hugh Henry

Dr. Hugh Henry received his PhD in physics from the University of Virginia in 1971, retired after 26 years at Varian Medical Systems, and currently serves as lecturer in physics at Northern Kentucky University in Highland Heights, KY.

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