AHS 2012 Lecture #1 (Dan Lieberman) – What are We Adapated For
I don’t know Dan Lieberman. I’ve never read anything by him, and I haven’t yet met him.
That’s my loss.
Here’s a quick recap of what Dan addressed:
The primary question Dan asked is “What is Adaptation” and “Why Does it Matter in our Modern Context?” He, of course, said it much more eloquently, but those are the critical questions.
Adaptation, in Dan’s words, is a useful feature, shaped by natural selection, that promotes the transfer of genes to the next generation. In other words, adaptation is entirely focused on getting to the next generation.
Adapations involve trade-offs and are imperfect, and Dan contended that there are 5 primary principles for how we can think about adaptations with respect to modern human health and medicine:
1. Many modern illnesses are “mismatch conditions.” A “mismatch condition” is a problem that is caused by using the human body in a way for which it was not adapted. One primary example of this is leading an inactive, sedentary life. The human body is adapted to essentially wasting away if it isn’t physically stressed on an ongoing basis. This made sense when humans were short on food and forced to exercise and move a great deal. In those circumstances, it makes sense not to keep any excess weight, muscle, or tissue that isn’t needed, because keeping that tissue requires energy.
2. Adaptations always evolve to promote “fitness,” but not necessarily health. In this context, however, fitness is our ability to pass on our genes to the next generation (i.e., our ability to have healthy, surviving offspring). One primary example of this is human fatness. Most primates hover around a “healthy” 5% body fat, but even very active hutner-gather women hover between 15-20% body fat. The reason for the higher body fat percentage is because it requires a great deal of energy to be pregnant and give birth. The higher level of body fat allows humans to give birth more frequently and more often.
3. There was no SINGLE environment of evolutionary adaptiveness. This is a fairly obvious and non-contentious point. Humans evolved in different ways over the past 6 million years in many different parts of the world. Modern humans are some conglomeration of a variety of these evolutions. This is important because it also means that there is no single answer to modes human health and medicine.
4. Evolution has not stopped, but cultural adaptations are overwhelming natural selection. Again, this is not particularly controversial. It’s clear that many of the natural selection pressures have been removed from modern life. Our ability to have offspring is no longer entirely dependent on our ability to adapt. One can be very unhealthy and (often with the help of modern medicine) live quite long enough to have kids.
5. Many so-called “symptoms” may actually be adaptations. This is particularly important, although Dan didn’t spend too long on this point. Things like fever, shin splints, and nausea are actually human adaptations that allow a human to recover from illness, learn not to run badly, or remember not to eat a particularly toxic food (for instance). However, modern medicine often treats these adaptations as something to be cured.
The last third of Dan’s talk was focused on a case study of human inactivity. Dan garnered a great deal of information and literature to not only support the notion that physical inactivity is a huge “mismatch,” but also to show how thinking about these modern mismatches might change the way that we approach modern human health and medicine.
I don’t say this lightly, but the best thing about Dan’s talk was that it was both funny and interesting. We need more people who can talk about the science and the research in a way that is accessible and not boring and monotonous. This is very important.
Apart from that, however, I think Dan did 2 other important things.
First, I like having a fairly simple but structured way to think about evolution, adaptation, and mismatch. It’s an easy way to talk about health issues, the potential reasons behind those health issues, and also the potential solutions.
Second, Dan really presents a great case for a significantly higher amount of exercise. This is a somewhat contentious topic, and many currently argue that we don’t need that much exercise each week to achieve close to optimal health. Dan thinks otherwise, and I have to say that he’s pretty compelling, both from a scientific and also an evolutionary perspective.
Again, I really enjoyed Dan’s talk, and if it’s put online after the conference, I highly suggest watching it.
Hopefully, we’ll also be able to get Dan into one of the upcoming issues of Paleo Living. Exciting.