About the author
Christian Thoma is a former food regulatory scientist who has recently chosen to pursue his hobby of exercise science by undertaking a PhD on exercise and non-alcoholic fatty liver disease. He is an American College of Sports Medicine certified Clinical Exercise Specialist, holds a BSc in microbiology and immunology, and an MSc in human nutrition, both from the University of Otago, Dunedin, New Zealand. He presently resides in the UK, where he spends his spare time purchasing exercise equipment and any reading/viewing materials that use evidence-based reasoning to advocate a change in the status quo in nutrition, exercise, and how science is conducted and reported.
Cave Man is SO Back in Style!
It has become somewhat popular to explain things in both biological and psychological sciences in terms of their evolutionary basis. In the biological sciences, advocates of the paleolithic diet spring to mind. In psychology, the often used example is how chronic stress is the result of a fight or flight response suited to acute danger now being continuously activated by everything from time pressure to road rage. You'll no doubt have your own examples you've heard, read, or even thought up. I'll focus on the biology as I'm not a psychologist.
Cave Man Debate: Proceed With Caution
I'm convinced by the evidence that we did indeed evolve, and am not here to start a debate about that any more than I'm prepared to debate a man claiming to be Julius Caesar demanding the keys to Rome. Nor do I intend to argue that the various theories based on evolutionary concepts are wrong. I would, however, caution anyone from accepting a line of reasoning that starts with "we evolved to," purely because it sounds plausible/sensible. The reasons that I think you should be cautious are that: 1) it's really hard to know how people conducted their lives 20,000 years ago; 2) even if we did evolve in this or that way, it doesn't mean that is optimal - it just means it was good enough for our ancestors to survive long enough to reproduce; and 3) we haven't stopped evolving and we don't have a good handle on how quickly it happens.
One Size Does Not Fit All
Anthropologists do have their techniques to study past cultures and they do an amazing job given what little they often have to work with. It is, however, very difficult to verify the hypotheses they form. Even where these are robust (or we assume them to be), our ancestors didn't all live in the same places, in the same way, eating the same food. Therefore, to promote one lifestyle or diet purely on the basis that this is how our ancestors lived lacks broader perspective.
Because Cave Men Survived, Doesn't Make Their Lifestyles Optimal
Evolution is driven by reproduction. The strongest don't always survive, however the genes of those that reproduce certainly do. The easier it is to survive in a given environment, the greater the diversity of people who pass on their genes. Ecosystems appear to move towards a state of balance, or they collapse. These systems don't create the 'best' anything as that would create imbalance. Look at new species introduced into ecosystems where they have no predators and/or an abundant food supply - they thrive and take over. To suggest that we will thrive because we go back to what was adequate for our survival ignores this one obvious observation entirely.
As I said above, the evidence for processes of natural selection has certainly convinced me. But the details are an area of ongoing intense study. There is evidence that the nutritional state of the mother during pregnancy has effects on her grandchildren and perhaps beyond in ways that are not part of the classically understood models of the passing on of genes. We simply don't know how much and in what way we may have evolved in the last 10, 20, or 50 thousand years even though there is good reason to view these as short time frames in evolutionary terms.
Is the Total Equal to the Sum of the Parts?
Being able to devise a hypothesis based on evolutionary reason may well be a good justification for further study, but it shouldn't be regarded as sufficient evidence in itself. It may be that a diet based on what is believed about pre-agriculutral times is healthy, or that a lifestyle involving movement similar in quality and quantity of that performed by stone-aged tribes is healthy. It may also be that it wasn't so much the diet as the calorie cycling - from bountiful to limited - has value over the actual foods, their ratios or quantities. Being more active/less sedentary is good advice, but the movement quantities of our ancestors may lead to considerable wear and tear over the long life-spans many now lead. Lastly, the need for food probably drove activity, this is no longer the case. There is no guarantee that if one takes a component out of one system and slots it into another it will work the same way or even be appropriate at all.
"Natural" Does Not Always Mean Safe or Beneficial
This brings me to the closely related assumptions by many that 'natural' is good and 'unnatural' or 'man-made' is harmful. Presumably because we evolved for the former and not the latter. I used to work for a food regulatory agency. We proposed legislation and as such had to be very clear with our definitions as they needed to be enforceable in court. If you can't define what you do and what you don't mean without creating a very long list, forget it. Funnily enough, we never managed to define 'natural'. It means one thing to you, one thing to your friend, and something slightly different to your neighbour. Definitions aside, nature abounds with very toxic things from animal and insect venom, bacterial and fungal toxins, to volcanic ash and sulphuric acid lakes. Even some of the nastiest man-made stuff is just a concentrated version of nature's finest. In toxicology, our motto was the difference between a medicine and a poison is the dose. Do be careful about what you put in your body and advise clients as to what they put in theirs, but please don't assume that if it's natural in your definition it's also health promoting.
Take Home Message
My take home message is always look at the evidence and think about it critically. Don't fall prey to things that suit your biases. And be very wary of any reasoning based on a philosophy such as natural is good and man-made is bad or, if it worked for our ancestors, it will do us all good now. Take advantage of what science, viewed with a critical and inquisitive eye, has to offer. We don't yet have a thorough enough grasp of physiology to be able to consistently predict how eating or doing something will affect us, and reality doesn't always fit into nice philosophical frameworks.
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