General Remarks on Tradeoffs
Evolutionary adaptation often involves striking a tradeoff between competing design criteria. Evolution has fine-tuned us for life in the ancestral environment, which, for the most part, was a life as a member of a hunter-gatherer tribe roaming the African savannah. Life in contemporary society differs in many ways from life in the environment of evolutionary adaptedness. Modern conditions are too recent for our species to have fully adapted to them, which means that the tradeoffs evolution struck may no longer be optimal today.
In evolutionary biology, the “environment of evolutionary adaptedness” (EEA) refers not to a particular time or place, but to the environment in which a species evolved and to which it is adapted (Hagen 2002). It includes both inanimate and animate aspects of the environment, such as climate, vegetation, prey, predators, pathogens, and the social environment of conspecifics. We can also think of the EEA as the set of all evolutionary pressures faced by the ancestors of the species over recent evolutionary time—in the case of humans, at least 200,000 years (Hagen
2002). Hunting, gathering of fruits and nuts, courtship, parasites, and hand-to-hand combat with wild animals and enemy tribes were elements of the EEA; speeding cars, high levels of trans fats, concrete ghettos, and tax return forms were not.
The import of this for the evolution heuristic is that even if the human organism were a wonderfully well-designed system for life in the EEA, it may not in all respects be well designed for life in contemporary society. If we can identify specific changes to our environment that have shifted the optimal tradeoff point between competing design desiderata in a certain direction, we may be able to find relatively easy interventions that could “retune” the tradeoff to a point that is closer to its present optimum. Such retuning interventions might be among the low-hanging fruits on the enhancement tree, fruits within reach even in the absence of super-advanced medical technology.
Proposed enhancements aiming to retune altered tradeoffs can often meet the EOC. The new trait that the enhancement gives us might have been maladaptive in the EEA even though it would be adaptive now. Alternatively, the new trait might be intrinsically associated with another trait that was maladaptive in the EEA but has become less disadvantageous (or even beneficial) in the modern environment, so that the terms of the tradeoff have shifted. In either case, the enhancement could be adaptive in the current environment without having been so in the EEA, which would explain why we do not have that trait, allowing us to meet the EOC.
We can roughly distinguish two ways in which tradeoffs can change: new resources may have become available that were absent, or available only at great cost, in the EEA, or the demands placed on one of the subsystems of the human organism may have changed since we left the EEA. Let us consider these two possibilities in turn and look at some examples.