Behavioral ecology and evolutionary psychology are really about why people would disposed to respond to their environments in particular ways. And rich and poor people - even within the same city - experience very different environments. The resources available to them, the security of their existences, the possible futures, are all very different. So it should not surprise us that their behaviours end up different. However, evolutionary psychology and behavioral ecology help us understand why their behaviours might take the paths that they do.
Well, there is probably no strategy for living which works in every environment. Sometimes the bold individual is favoured, and sometimes the cautious one. The consequence of this is that in every human population today there is a mix of different personality types. It's true in other species too.
Humans are specialised for joint foraging and production. In no society do humans survive by each individual just going out alone and foraging in an uncoordinated way. Instead, groups work together to hunt, fish and forage cooperatively. In my view the origins of language lie in bringing about the behavioural coordination which is required for this kind of joint effort. Once it existed though, language is such a remarkably efficient adaptation that individuals could start coordinating their behaviour in many other novel ways too, and that is how humans were able to become ecologically dominant and invent ever more sophisticated new technologies.
I think the psychology literature overemphasises the importance of happiness as a personal and societal goal. It's part of the individualism and consumerism of our age. There are plenty of other important goals to pursue, like justice, sustainability, meaning, knowledge, truth. These don't have that much to do with happiness. Happiness and sadness arise from very crude mechanisms of responding to immediate gain and loss, which we share with other animals. It would be a very impoverished human life where everything was reduced to that.
There is some evidence supporting the idea that the same characteristics which make people vulnerable to psychotic illness also make them excel in creative endeavours. So it is not that creative people are psychotic, or psychotic people are creative, but that the same underlying traits lead in some environments to creative functioning, and in other environments to serious mental illness. The evidence comes from things like fact that the families of writers and artists often contain other people who have suffered psychotic problems.
Of course, becoming ill is never favoured by evolution, by definition. But evolution can favour sickness behaviour, which is when an animal in poor condition slows its movement, hides and is not motivated to do anything until it has healed. Also, evolution can favour hibernation, which means again slowing down, sleeping, not wanting to do anything, whilst the environmental conditions are unfavourable. These examples can help us think about depression; mild depression might represent the working of mechanisms for conserving energy and avoiding stimulation whilst the environment is unfavourable or the individual is in a poor state. That is why mild depression so often follows loss or physical illness. However, this does not account for the most serious clinical cases; here, it may be that adaptive mechanisms have become dysregulated.
As I said in my answer to question 3, humans are specialized for social foraging. This necessarily involves exchange of information and of resources. Thus, it is very deep in the human way of life that we share ideas and plans and tools in a social network. Modern technologies and population densities have just allowed us to do this on a vastly greater scale, and in a way which has extraordinary emergent consequences, such as economic growth, the spread of cultural norms, and creation of arts and sciences.
I am still fascinated by human social behaviour, so I am working again on trying to understand when people will cooperate with one another and when they will not. I study this both in the field and using theoretical models.
1. ¿Cómo nos ayudan la ecología conductual y la psicología evolucionista a explicar las diferencias de comportamiento entre los miembros de las diversas clases sociales?