Paleo diets have been increasingly popular over the last few years. The idea is that, for optimal health, we should be eating the things that we are evolutionarily adapted to eat. Those foods pre-date the onset of large-scale agriculture 10-12,000 years ago. So grains and modern fruits and vegetables play little or no role in someone who has “gone paleo.”
My recollection from college courses years ago is that average lifespan in paleolithic times was perhaps 25-30 years, or less. If you’re going to die at 25, it may not matter if you eat a lot of wooly mammath, berries, insects, cholesterol, saturated fats, Doritos, Ding Dongs, or Cheetos. The diseases of civilization we worry about today—coronary heart disease, high blood pressure, cancer, dementia, type 2 diabetes, etc.—don’t usually appear until after age 30. Paleolithic Man worried more about starvation.
Jenny Ruhl, at her Diabetes Update blog, recently put much more critical thought than I into the concept of paleo diets. Recommended reading.
For purposes of discussion, let’s assume that human evolution actually occurred over millions, or at least hundreds of thousands, of years. In other words, assume that God didn’t make Adam and Eve in human form in one day.
The theory of evolution proposes that genes that allow an animal to live and reproduce more vigorously in a particular environment will be passed on to the animal’s offspring. Nature will select those genes to spread through the animal population over time, assuming the environment doesn’t change. The offspring with those genes will be able to compete with other animals more successfully for food, shelter, and mates. Factors that promote the persistence and inheritance of specific genes are called “selection pressure.”
Here’s an example of selection pressure. Remember when you were in grade school on the playground, some people could naturally run faster than others? Were you one of the fast ones? If you’ve never seen it for yourself, take my word for it: Some people are naturally gifted with athletic genes.
Let’s say you and I are outside collecting berries and nuts in paleolithic times. A saber-toothed tiger spots us and charges, hungry for a meal. You don’t have to outrun the tiger: you just have to outrun me. I’m slower than you, and get eaten. I can no longer pass on my slow-running genes to the next generation. You live another day and pass on your fast-running genes to your children.
Viola! Natural selection, via selection pressure, has promoted your genes over mine.
[The tiger also passes on her genes since she was fast and smart enough to catch me, preventing starvation of her and her offspring.]
[I’m 99% sure I wrote the preceeding few paragraphs originally about a year ago. My notes, however, hint that they may have been written by Dr. J., a regular contributor at CalorieLab. Dr. J., let me know if I’ve plagiarized you and I’ll give you full credit and delete my writing.]
The paleo diet rationale seems to be based on an evolutionary argument: Certain foods were available to us during 99% of our evolution, so our bodies are adapted to work optimally with them. For example, humans/humanoids/higher primates who were not suited to the available food did not survive and reproduce, so their genes were not passed on to us.
For most of human existence, maximum lifespan was probably 25-30 years, on average. If that’s as long as you’re going to live, it may not matter much what you eat. Eat paleo, vegetarian, McDonald’s, Atkins, or Mediterranean. Most diet-related conditions except overweight and under-nutrition are not going to be an issue before age 30.
[The modern paleos argue that infant and childhood mortality were extremely high in paleolithic times. If you survived childhood, you could easily live to be 50+.]
But now we live to be 80, long enough for diet-related diseases to appear. We have cancer, heart attacks, and strokes that paleo man never saw because he died of trauma or infection or starvation. We even see the expression of genes that were not subjected to survival or selection pressure: Alzheimers disease, Huntingtons chorea, some breast cancers, etc. People with genes for these diseases reproduce before the genes do their damage.
In other words, we carry genes that don’t matter if you die at age 30. If you live longer, they express themselves, and I believe we can modify their expression through diet and lifestyle. And not necessarily the paleo diet.
I’m still thinking it through.