The Evolutionary Psychology FAQ

Edward H. Hagen, Institute for Theoretical Biology, Berlin

What is the EEA and why is it important? (general answer)

The Environment of Evolutionary Adaptedness. This phrase, first coined by John Bowlby of attachment theory fame, has been the source of much confusion and controversy. First of all, the EEA is NOT a specific time or place. Roughly, it is the environment to which a species is adapted. Animals that lived in different environments or made their livings in different ways faced different reproductive problems, and that's why all animals aren't the same. Fish faced different problems than did butterflies, and as a result they have different adaptations. The EEA for any specific organism is the set of reproductive problems faced by members of that species over evolutionary time. The EEA for a particular species of fish is likely to be completely different than the EEA for a particular species of butterfly, even if those species both evolved in the same locations over the same periods of time. Each of these species faced reproductive problems that the other didn't, and thus their EEA's are different. The EEA concept is very similar to the notion of 'niche' in evolutionary biology.

I have used the past tense when referring to the solving of reproductive problems because adaptations evolved over a large number of generations and are therefore "tuned" to reliable aspects of past environments (see the next section). If the environment changes, then the adaptation may be "out of tune" with the present environment and fail to properly perform its reproductive function.

The EEA concept is extremely important for understanding the functional properties of organisms, including the functional organization of the human brain. As outlined in the previous section, the functional properties of organisms arise by the process of evolution by natural selection. This means that the functions that organisms have are precisely those that solved long standing, recurrent reproductive problems. Reproductive problems are all the various things organisms had to do to survive and reproduce in a particular environment over evolutionary time--find food, find mates, avoid predators, combat pathogens, etc.

This observation is particularly important for understanding the functional organization of the human brain. Because we cannot (yet) directly study the wiring of the brain (except in a very few cases), we need another 'window' or set of tools for perceiving brain functions. Darwin's theory provides this window. If we can specify all the reproductive problems faced by our ancestors (i.e., if we can specify the human EEA), we can specify all the potential functions that our bodies and brains could have, in principle. With respect to the brain in particular, if we can specify all the reproductive problems involving information processing, we can specify all the possible psychological mechanisms that could have evolved. Whether humans possess any particular psychological mechanism (i.e., an ability to solve a particular reproductive problem involving information processing), becomes an empirical question. Fortunately, it is much easier to find something if you have some idea what you are looking for. Studying the past is, at present, easier than studying brain wiring. The EEA concept therefore provides a much needed tool for determining, a priori, what kinds of functions, or mechanisms, the human brain is likely to have: the human brain solves the reproductive problems posed by past environments; it allows us to do all the things we needed to do to survive and reproduce in ancestral environments--find food, find mates, detect and avoid predators and other dangerous animals, etc. We can understand the functional organization of human bodies and brains precisely to the extent that we can understand the human EEA.

Copyright 1999-2002 Edward H. Hagen