Thesis #3. Health and adaptation thus reflect the action of natural selection on a population in its previous environments, not its present environment, when these differ.
For the purpose of re-founding medicine scientifically, theses 2 and 3 direct us to pay particular attention to the sequences of environments that humans have been exposed to during our evolutionary history. It is fanciful to suppose that, because our species has been in existence for several hundred thousand years of evolution, it is fully adapted to any environmental conditions that it might encounter.
And this point is still more profoundly important when we consider the extent to which our environments have been transformed over the last century of rapid technological change. Just four or five human generations are far too few to have given us adequate adaptations to our present environment. Instead, what adaptations we have, and thus the conditions under which our fitness is likely to have been maximized, reflect the impact of natural selection on our evolution prior to the advent of our present, highly technological, industrial environment.
Thus evolution by natural selection has supplied us with adaptations only to environments in which we have lived for many centuries. But this does not then immediately imply any simple or obvious set of inferences about how medicine can best manage human health or treat our diseases. For the action of natural selection is subject to still other limitations, well beyond the vagaries of environmental history.
Editorial from Rob – Sitting is in fact very bad for us – we are designed to be active and to move all day – here is some useful research about the costs of sitting
It is these further limitations on the action of natural selection that we turn to next.
This thesis restates the mismatch hypothesis; whose core element is that genes which were adaptive (+ selection) or neutral (0 selection) in past environments may be deleterious (- selection) in the present environment. Strictly speaking mismatch need not impact fitness, since the present effect might just be one that creates discomfort or pain.
I have been concerned lately with how the mismatch hypothesis can be employed to explain the persistant health disparities of socially subordinated groups. Thus I argue that a crucial aspect of that present industrial environment is its increased social hierarchy. Our ancestors evolved in small groups, composed of many related individuals. Undoubtedly there were some forms of heirarchy, but nothing like what we experienced during the founding of civilizations (via agricultural surplus.) This hierarchy got worse with the development of slave and feudal societies and changed form with the coming of capitalism. Thus Marx’s class struggle is part of the mismatch of the industrial/agricultural ages versus the ancient hunter/gatherer environment. By this logic, socially subordinated groups/individuals should always exhibit worse health and greater mortality differentials. This may have particular utility with regards to understanding mental diseases (especially major depressive disorders.) The take home message here is that any real policy to address health disparities must always take into account issues of social justice.
Joe I think that you are correct – Michael includes ALL environments in his perspective. I will be posting a lot on this important part of this topic on our related site The Missing Human Manual – I will be using Dr Michael Marmot as the over context and then bring in work by Sapolsky on social stress, Willms on how parenting affects our resilience from infancy. The evidence is clear our place in the world has a major impact on health. True for all social animals such as apes and even more for us as we can worry about the past and the future too.
The Industrial world has I think separated us from our core work – raising our kids – created steep hierarchies where many have no control or genuine identity. Is this why we consume goods and eat bad food too? To find a role in a world that offers none?
Hard though to change how our current culture is set up on our own. But I see signs of hope. Are not many Freelancers really Hunter Gatherers? I know that I am. As a HG I have a tribe too – about the same size as my ancestral one – so I also have a reputational role as I would have had. We can chose to make raising our kids and the family important again – with the dying of the state as the family of last resort and the loss of pensions – we may have no choice. The web has made all of this easier too. Any way I go on too long and close by agreeing with you – our ancestral social environment had a less steep hierarchy and offered roles and value for all. Agriculture changed all of that.
Our food system may be the clue to our social culture