Is The Digital Age Inhabited by Stone-Age People?
Human brains change in surprising ways.
Posted May 02, 2017
Then there is the narrative of testosterone-crazed youths who feel their oats by committing assaults and homicides.
Although such stories are not completely out of touch with reality, the overall scenario of humans being archaic creatures who are ill-suited for modern life is exaggerated.
Adaptations of Modern Humans
Even in the ten millennia of agriculture, people underwent genetic changes. Herders developed adult lactose tolerance so that they could digest cow's milk (1). Cereal farmers of northern Europe evolved pale skin as a way of maximizing vitamin D production in the skin given that this was deficient in a diet heavy on cereals.
Such gene-based instances of adaptation are rare, however. Changes in brain biology in response to changing environmental conditions are more impressive.
Hearing Lost, IQ Gained, Skills Etched in the Brain
One profound change in the lives of our hunting ancestors was the domestication of dogs that helped us to detect large game animals from a distance. Dogs have fantastically sensitive hearing. When they were domesticated some 50,000 years ago, there was a decline in human hearing ability, so substantial that it allowed sensory areas of the brain to shrink sufficiently that the change is visible in skulls from the period (2).
This transition was likely affected by a relaxation of natural selection for good hearing, although we are learning so much about brain flexibility that this is debatable. Animal experiments from four decades ago revealed that if animals are raised in more cognitively stimulating environments, their brains grow slightly larger, that is analogous to muscles growing larger with exercise.
Similar phenomena apply to humans: as economies develop and as our physical, and social, environments grow more complex, IQ scores increase (a phenomenon known as the Flynn effect).
Now, we are learning that the brain adjusts in complex ways to the altered demands placed upon it.
So the brain of a reader functions very differently from the brain of someone who never learned to read. Similarly, learning to play a musical instrument alters how control of the fingers is represented in the motor cortex. Research has also shown that London taxicab drivers (3) who master navigating the streets of this large city use more energy in their amygdala.
Each of these phenomena shows that the brain adapts to our routine activities in remarkable, and helpful, ways. Of course, changes in the brain are just one aspect of how we adjust to fit in with modern life. Most social scientists are more interested in how we adapt to the changing social landscape. Unfortunately, there has been less research in this field but the results so far have been tantalizing.
Amongst many social animals, males experience a tradeoff between siring offspring and parental care. For barn swallows, physically attractive males (those having long symmetrical forked tails) spend less time caring for the young and more time cheating on their partners (4).
Amongst humans, this tradeoff plays out in many different ways. For college students, there is a choice between time spent studying and time spent going out and having a good time.
In recent decades, male students in particular have emphasized partying over studying with a consequent decline in college degrees earned that are now well below those of females (5).
Of course, many explanations have been offered for male academic under performance but few experts connect it to sexual behavior. Yet, there has been a large increase in sexual behavior amongst single people facilitated by widespread use of effective contraceptives amongst other factors.
The existence of a large pool of sexually active single women means that men do not have to marry to enjoy a satisfactory sex life, as had been true in earlier generations. So why work hard at developing a career to make themselves desirable as marriage material if they can attract sex partners now?
At the same time that male career effort is dropping off, female academic performance has picked up. Evidently, they can no longer rely upon husbands to earn income for the couple. So both women and men adjust their sexual behavior to match changing adaptive landscapes over time. The same is true of differences between societies.
Without dwelling on how humans change adaptively to match the current social environment, there is little doubt that we do. So the much-repeated claim that modern humans are cave people in business suits has to be wrong.
1 Henrich, J. (2015). The secret of our success: How culture is driving human evolution domesticating our species and making us smarter. Princeton, NJ: Princeton University Press.
2 Groves, C. P. (1999). The advantages and disadvantages of being domesticated. Perspectives in Human Biology, 4, 1-12.
3 Maguire, E. A., Gadian, D. G., Johnsrude, I. S., Good. C. D., Ashburner, J. Frackowiac, R. S., and Frith, C. D. (2000). Navigation-related strutural change in the hippocampi of taxi drivers. Proceedings of the National Academy of Sciences, 97(8), 4398-4403. doi:10:1073/pnas.070039597.
4 Moller, A. P., and Tegelstrom, H. (1977). Extra-pair paternity and ornamentation in the barn swallow Hirundo rustica. Behavioral Ecology and Sociobiology, 41, 353-360.
5 Caplow, T., Hicks, L., & Wattenberg, B. J. (2001). The first measured century: An illustrated guide to trends in America, 1900-2000. La Vergne: TX: AEI Press.