Happy April 1st! This post is part of April Cools Club: an April 1st effort to publish genuine essays on unexpected topics.
I want to tell you about a fascinating topic of adaptive plasticity and life history theory. I haven’t read anything about this anymore since 2014 but the ideas have kept a place in my head (lived there rent free? a weird expression). This is also a free day for me, so I’m going to put minimal effort in writing about this topic, I am going to write without consulting even wikipedia. Expect most of this to be wrong, outdated or accidentily correct.
What follows is a mix of science, post-hoc hypothesis, possibly pseudoscience, and since it is partly genetics, a good mix of racism.
resilience and adaptation
Living creatures, animals, plants, fungi, and bacteria are remarkibly resilient. They can thrive even in harsh conditions. This is cool and attributed to natural selection: eg better fitted creatures get more babies in successive generations. Their genes are passed on.
But in fact creatures of the same species can live in very different conditions. The same species of animal can live in starkly different environments. They do that by changing the way they operate. They change their behavior. This only works in young animals though. This is where the idea of adaptive plasticity comes from. The idea is that young animals have many paths available, the genes allow multiple ways of expression and only under certain environmental cues behavior or gene expression is seen. The idea of adaptive plasticity is that young animals (let’s stick to animals for now, similar things work for plants and bacteria etc.) have many options available and the environmental cues let the body know which options to choose. Importantly once a base setting has been ‘chosen’ it is harder to get out of that groove. If your visualise the possibilities as a landscape, young animals live in a flat landscape, they can go into many directions. the older you get, the more hills come into the landscape, restricting your directions to only the valleys. For example if a base setting sets your sensitivity to outside cues higher your body reacts faster to stimuli, which could mean higher adrenalin responses and more receptors of that type etc.
An related idea to adaptive plasticity is life history theory. The hypothesis is (I believe) something like this: environmental cues shape the life history (the path from birth to adult to death) of an animal; the pace of life changes. In adverse circumstances it is more advantagious for genes to spread earlier, to have more recombinations in the hope that in the new combinations are better adapted individuals for that environment.
For example: in a hostile environment it is more adaptive to be very vigilant. but this has a cost, more wear and tear on the body means the body gets older faster. It also means that you need to have offspring early, because you might not live so long. I believe there were some studies that showed that animals in environments with high uncertainty reached sexual maturity earlier and aged and died earlier. There was even some support for that idea in humans, but that gets tricky very fast, see below.
Applying these ideas to humans
I found the concept of early plasticity and getting stuck in a groove quite interesting. This would make many lifestyle diseases much more interesting, maybe your body is mismatched to its current environment? Early life can have strong effects on later life. What if we look at stress effects on the human body? There are remarkable differences in how people respond to acute and prolonged stress. Some people get heart diseases, others don’t. Maybe we can group and translate the types of responses into adaptive plasticity earlier in life.
It becomes very tricky when we try to apply these ideas to humans. There were some studies suggesting that girls who grew up in harscher conditions would have their first period earlier. Does that suggest an alternate life history path, does that suggest they have children earlier because their body noticed they live in uncertain surroundings? There are many alternative explanantions, we do not put children into fully controlled experiments over their entire life. There are confounding variables like income or location. You risk creating hypotheses that are untestable and talking about people like this makes them unchangeable. You create a sort of biological determinism “Jack can’t change the way he eats because of his early youth.”
But people are remarkebly plastic, we can change and choose to act differently. Post hoc explanations always fit very nicely on history. Does life history theory or ideas about adaptive plasticity provide insights into treatments? Are there ways we can determine what behaviors in humans are determined by adaptive plasticity? Can we create testable hypothesis about people? I don’t know.
So there we are, some ideas about adaptive plasticity are interesting, some are risky and although I think about these ideas at least once a quarter, they have no real influence on my work.
I should really read a book about it, maybe.