The Evolutionary Psychology FAQ

Edward H. Hagen, Institute for Theoretical Biology, Berlin

Isn't it true that we can't know what happened in the distant past, so the EEA concept is useless?

No! It is a common misconception that the EEA refers to aspects of the past that differ from the present. In fact, the EEA refers the aspects of the past whether or not they correspond to aspects of the present. For any living species, most aspects of its EEA will correspond closely to aspects of its present environment, otherwise it would go extinct; if the present environment of any organism differs too much from its EEA, its functions will most probably fail to ensure survival and reproduction.

There are many mundane facts about the past that we know to be true (which also happen to be true of the present): there was gravity, sunlight, oxygen, plants, animals, parasites, cliffs, rivers, lakes, predators, toxins, men, women, children, old people, parents, brothers and sisters, mates, rocks, sticks, trees, faces, etc., etc. We also know that women got pregnant and men didn't. This single fact about the EEA is the foundation for much research on mating strategies in both humans and other animals. Pregnancy involves numerous costs, and we therefore expect that females in many species will be more picky about mating than will males. This prediction has strong empirical support for both humans and other animals.

There are also several aspects of the human EEA that differ from most present human environments. We also know that population densities were much lower than today, that most societies were very probably kin-based, that child mortality rates were very probably much higher than today. However, humans still took more than a dozen years to reach sexual maturity, and fathers were less certain of paternity than mothers were of maternity (as they are today, absent a genetic test). These latter facts form the foundation for considerable research into differential parental investment. Human offspring require enormous investment to reach sexual maturity. If half of one's children were likely to die, parents needed to be able to target their investment towards the healthiest, most viable offspring. Similarly, males should have targeted their investment at offspring that were likely to be their own. Both of these hypotheses have found considerable support among both humans and other animals.

The EEA concept is an essential and logically necessary aspect of the theory of natural selection. We have lungs because there was an oxygen atmosphere in the *past.* Should our atmosphere suddenly disappear we would still have lungs, but they would be useless. If we could truly say *nothing* about the past, we would have to abandon the concept of adaptation. Fortunately, archaeologists, paleontologists, paleoanthropologists, historians, detectives, and cosmologists all make a living studying the past, so the problem obviously isn't insurmountable.

Copyright 1999-2002 Edward H. Hagen