Musings on human evolution

I love when science provides space for fun, and it so often does. Some time ago, I read Richard Lenski and Terence Burnham’s 2017 paper in the Journal of Bioeconomics entitled “Experimental evolution of bacteria across 60,000 generations, and what it might mean for economics and human decision-making,” (1) and it was one of those papers where I could tell that they had a blast writing it. They give an overview of the Long-Term Evolution Experiment (LTEE), which Lenski has running for longer than I have been alive (if it were a scientist, it could be applying for postdocs by now), and how understanding how bacteria evolve may or may not help us understand some of the random stuff people do.

Because, as behavioral economists know, the random and illogical things that people do actually show patterns and have plausible and increasingly evidence-backed explanations (yes, I am a fan of the Freakonomics Radio podcast).

My favorite point that Lenski and Burnham make in the paper is that many of the human inventions that we consider commonplace and integral to our lives, like stock exchanges, colonoscopies, and agriculture, have in an evolutionary sense not been around for very long. They speculate that since the E. coli of the LTEE are still adapting to the unchanging environment in which they live after 60,000 generations, and agriculture has only been around for 600 human generations (Lenski and Burnham 2017, Table 1), humans it may be hasty to assume that humans are extremely well adapted to that situation. To be clear, they are not, as far as I can tell, advocating shunning agriculture to return to a more “natural” or “ancestral” diet. Environments change all the time, and organisms adapt. I think they included agriculture in this table as a contrast to the other entries, for example the New York Stock Exchange, which has been around for about 10 human generations. Only 10. Maybe that is a factor in why humans aren’t generally great investors. We know that beneficial mutations in bacteria can arise relatively quickly, but it still takes many generations for them to increase in frequency in populations that reach hundreds of millions or billions of individuals (2), although the specifics depend on the exact experiment.

I also recently listened to the audio book of “Why Buddhism is True” by Robert Wright, in which he describes parallels between Buddhist nonreligious teachings/practices and current psychology research. One idea that he talks about is how some of our experiences, such as anxiety about giving a presentation to a large audience, may be due to a mismatch between the environment we experience and the one that evolution has prepared us for. It seems unlikely that speaking in front of large crowds was a situation encountered by our distant ancestors, and so the anxious reaction may not be adaptive.

All of this makes me think about how many organisms drastically change their own local environment (like yeast producing alcohol) in ways that force them to either adapt or die. I think often when we talk about the environmental changes that affect organisms an form part of the natural selection they experience, we refer to conditions imposed by an experimenter in a lab or to large-scale global processes. But it’s also interesting to think about how what organisms themselves do can force them to adapt. Humans are intelligent organisms who are capable to a large extent of constructing their own environments, and the pace of change can be quite rapid both at the level of a whole country or society or at the level of an individual family/lineage. Of course, we can think about these changes and respond to them by making decisions and modifying our behavior. In this context, those might be considered plastic responses; however, our decisions and behavior seem to be influenced by our genetics. Is it possible that humans are not well adapted to their own intelligence?

My generation invented social media, and to our kids it will be completely normal, something they don’t question, part of the water in which they swim. However, I think it’s clear that we as a species are not currently able to use it to best effect, whether that be to achieve moral and human rights goals or the biological goal of, as Wright puts it (and yes, it’s reductionist), “getting our genes into the next generation.” If we were, there wouldn’t be so many stories of online dating gone awry.


  1. Lenski, R. E., & Burnham, T. C. (2017). Experimental evolution of bacteria across 60,000 generations, and what it might mean for economics and human decision-making. Journal of Bioeconomics, 1–18.
  2. Lenski, R. E., & Travisano, M. (1994). Dynamics of adaptation and diversification: a 10,000-generation experiment with bacterial populations. Proceedings of the National Academy of Sciences of the United States of America, 91(15), 6808–6814.


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