Evolutionary psychology is a field that examines human psychological traits through evolutionary glasses. Most human psychological traits are considered adaptations, the functional products of natural or sexual selection. This is tidily summarized in a quote from Cosmides and Tooby, two of the founders of the field:
Our modern skulls house a Stone Age mind.
The field, however, is quite controversial. Proponents tend to explain every aspect of the human psyche through evolutionary adaptation, whereas opponents often express the criticism that these are ‘just-so stories’. Between these two positions, of course, many more moderate ones are possible.
Now, a publication in PLoS Biology argues that evolutionary psychology itself should adapt to the knowledge gained from new findings in a variety of fields, ranging from evolutionary biology to cognitive neuroscience. Firstly, the authors identify the four basic tenets of evolutionary psychology.
- The environment of evolutionary adaptedness (or EEA). Basically, the idea that our modern psychological mechanisms have evolved in response to stable features in the environment of our ancestors (assumed to be the African Pleistocene savanna).
- Gradualism. According to evolutionary psychologists, our minds are built from co-adapted gene complexes that are unable to respond quickly to changes.
- Massive modularity. Since different adaptive problems require different solutions, the mind is assumed to consist out of different modules, eahc dealing with a different problem.
- Universal human nature. The evolved computational programmes in our brains produce a universal human nature.
Then, the authors continue with a reassessment of these four basic tenets in light of new evidence. For example, they quote evidence that the EEA wasn’t nearly as stable as previously thought, but rather a very variable environment, challenging the notion that our modern psychological mechanisms were formed in a stable EEA.
Continuing, evidence is presented that there has been substantial genetic change in human beings, even in the last 50,000 years. There is even evidence suggesting that recent human evolution has been affected by human-induced changes in the environment (such as diet, or living conditions). These rapid changes are a challenge for the gradualism, as interpreted by evolutionary psychologists.
To challenge the idea of universalism, the authors cite evidence stressing the ‘malleability’ of the human brain, meaning that experience affects neural circuitry and gene expression in that remarkably complex center of the nervous system. The influence of development is equally stressed, as is the view that the human brain is built through continuous interplay between the individual and the environment. Gene-culture coevolution is also mentioned, signifying that cultural practices could have influenced selection pressures on the human brain.
Finally, massive modularity is questioned, through the existence of domain-general mechanisms (such as associative learning, which is fairly widespread in the animal kingdom), and through the broad involvement of diverse neural structures in many psychological processes.
After this reassessment, the authors offer some advice on how evolutionary psychology could adapt to all this new evidence.
- The evolution of a character can be evaluated through the construction and testing of population genetic models, estimating and measuring the responses to selection, exploring the covariation of phenotypic traits or genetic variation with putative selective agents, and so forth, much as evolutionary biologists do.
- The new evidence suggests that human beings experience less adaptive lag (being adapted to an environment in the past, and not to the present one) than previously supposed. An examination of the relationship between evolved psychological mechanisms and reproductive success in modern environments might help in elucidating this. Analyses, optimality models and gene-culture coevolutionary models could also be used to research whether or not current human behavior is adaptive in present-day environments.
- The hypotheses of how the brain works can be compared to (cross-cultural) neuroscientific research, to see if this supports the hypotheses. Also, the genetic influence on brain formation and functioning could be involved here.
- Through the use of developmental genetics and psychology, the unlearned roots of cognition might be detected. This could also help in understanding how culturally and individually dependent concepts emerge.
The authors conclude:
None of the aforementioned scientific developments render evolutionary psychology unfeasible; they merely require that EP should change its daily practice. The key concepts of EP have led to a series of widely held assumptions (e.g., that human behaviour is unlikely to be adaptive in modern environments, that cognition is domain-specific, that there is a universal human nature), which with the benefit of hindsight we now know to be questionable. A modern EP would embrace a broader, more open, and multi-disciplinary theoretical framework, drawing on, rather than being isolated from, the full repertoire of knowledge and tools available in adjacent disciplines. Such a field would embrace the challenge of exploring empirically, for instance, to what extent human cognition is domain-general or domain specific, under what circumstances human behaviour is adaptive, how best to explain variation in human behaviour and cognition. The evidence from adjacent disciplines suggests that, if EP can reconsider its basic tenets, it will flourish as a scientific discipline.
Bolhuis, J.J.; Brown, G.R.; Richardson, R.C. and Laland, K. (2011). Darwin in Mind: New Opportunities for Evolutionary Psychology. PLoS Biology. 9(7): e1001109. doi:10.1371/journal.pbio.1001109. (Click here for the article)