Lately, I’ve had some interesting conversations with my friend Cathy, who is an artist and designer, about a whole raft of topics in medicine and science. She proclaims she has no scientific background, but she’s intensely curious about science and about what I write, so what else could a blogger want? Recently, we were discussing what constituted a good diet. I was trying to cut through what was myth and what was science, but sometimes it can be difficult to do so. My thoughts have always been that the human physiology is amazingly resilient, and as long as you have no chronic diseases, there is nothing one can do that will make the situation much better or much worse. Yes, maintaining levels of certain nutrients, such as vitamins C and D, iron, and others, are critical, but in the modern world, it’s almost impossible to miss out on those micronutrients.
A lot has been written about the diets of our ancestors, some of which are used to support whatever diet myth is trending at the time. Some vegans will claim that humans evolved to be vegetarians, but according to modern scientific research,
…since the evolutionary split between hominins and pongids approximately 7 million years ago, the available evidence shows that all species of hominins ate an omnivorous diet composed of minimally processed, wild-plant, and animal foods.
Some vegans will make a claim that humans “evolved” to be more vegetarian over the past few thousand years as we moved to an agrarian based culture, but that ignores the fact that evolution does not work that quickly on a species that has such a long lifespan and such a low population. There just is no scientific evidence that we evolved to be an exclusively vegetarian species.
On the other hand, there is a current fad for the paleolithic diet, which is based on the presumed ancient human diet of wild plants and animals that various hominid species habitually consumed during the Paleolithic era. It consists mainly of fish, grass-fed pasture raised meats, vegetables, fruit, fungi, roots, and nuts, and excludes grains, legumes, dairy products, salt, refined sugar, and processed oils. It really attempts to be scientific (much more so than vegans), but it seems to border on the edge of pseudoscience, and can be considered a fad. The diet itself probably has no more validity than any other diet (lots of anecdotal evidence of success, and no actual scientific clinical studies). The problem is that there is little evidence that paleolithic humans actually followed this diet (pdf), and their diet probably was in response to a huge seasonal, annual and longer duration environmental variability in food sources. But more than anything, is there any evidence that paleolithic humans lived longer or healthier than modern humans? Well, actually the Paleolithic lifespan was around 33 years, whereas modern man is around 67 years (varying from country to country). In other words, despite what many consider to be a terrible modern diet, we’re living longer (which is a result of a lot of things including hygiene, sanitation, medicines, vaccinations, and probably, better nutrition).
Coincidentally, Rob Dunn recently wrote an article in Scientific American about how chimpanzees eat in the wild. As a bit of background, chimps and bonobos (subtribe Panina), diverged from the line that lead to humans about 5-6 million years ago, and also shares about 97% of genetic material with humans. So they can be used as a proxy to human dietary preferences in the wild, though with a few million years of intervening evolution. But they can be a “crude measure” of our ancient diets, and can tell us an interesting story about what our modern diet should be.
A study by David Watts of the chimpanzee diet in the Kibale National Park in Uganda provided some detailed analysis of their diet in the wild:
- Diversity—The Kibale chimpanzees consumed around 102 species (and possibly many more) of plants either in the form of fruit or leaves. I don’t mean to be picky, but how many species of plants are in your local Whole Foods? And 20 different varieties of apples is still one species of apple. Human ancestors, in a planet with limited food resources, probably were just as fungible with their choices in plant foods as chimps. Modern humans just aren’t.
- Figs—Nearly half of all of the food consumed by chimps appears to be one or another kind of fig, fruit of the Ficus trees. Fig trees produce large amounts of fruit that are favored by a number of animals including most primates (including gorillas and many human cultures) and fruit bats. They are highly nutritious and contain a lot of energy, and have a wide number of ecological niches so that it would be distributed throughout the chimpanzee habitat. Early humans would have also found figs throughout their habitats in Africa, and figs were domesticated about 10,000 years ago, and have been a significant part of human agriculture in certain societies. It’s clear that along with increasing the number of plant varieties in our diet, we need to seriously increase the quantities of figs.
- Clumps—Chimps eat a wide variety of fruit throughout the year, but only eat one or two species of fruit at one time. So they might eat apples one day then oranges the next. So, they may eat what is “in season” or what is available. Many plants fruit seasonally, or even just for a few days, so the chimps eat what is available. There are a few continually fruiting plants, but they are rare, even in the tropics, so the chimps choose what is available.
- Meat–Although we focused on fruits and plant foods, chimps do eat meat, and are considered omnivores, just like their closely related cousins, humans. Chimps favor eating seven kinds of primates, including their favorite, red colobus monkeys along with three other mammal species. However, only 3% of the average chimp diet comes from meat. Given the availability of high energy plant foods, the energy expenditure required to acquire mammalian food probably is too high unless it’s easily obtained.
- Variety—One of the myths of our ancestral diets is that our ancestors ate some imagined ideal diet for their bodies. The observation of the chimp diet is that there isn’t an ideal diet, and they eat what they find. Even though figs are a significant portion of their diet, when they find no figs, they don’t eat figs, and change to something else. Some chimps eat more mammal meat than others, if that meat is available, not because of some evolutionary advantage to do so. The authors determined that although some species must eat a specific mix of foods to survive; chimps (and man) are not one of those species.
- Termites and ants (and their chitin)—Some chimps are good at eating termites, honey bees and driver ants. It’s unclear if chimps have any special ability to digest the chitin (exoskeleton of insects), but insects do have a lot of energy content. Again, chimps seem to have a broad choice in foods, and eat almost anything that is available.
- Other–Chimps at Kibale ate dirt. Gorillas eat wood and the occasional stone. What we might assume is not food seems to be food for the apes of the Kibale National Park. So, if you want to have an ancestral diet, apparently you have to open your mind to food sources that aren’t just plants and animals.
Before we head to the conclusions from this article, one thing is important. Figs. Really, we almost have to wonder if primates would not have evolved without figs. That fruit is a critically important part of the chimpanzee diet, and, given the ubiquity of the plant, we must presume that it was critical to early Hominims that evolved into modern humans. Maybe we shouldn’t be growing corn and wheat across the world, but fig trees. In fact, many human societies domesticated ficus for a fruit crop. Maybe I have to revise what I told Cathy, and tell her, “go to Whole Foods, and buy as many figs as you can eat, and eat them until you’re full.” I like figs. Maybe I’ll have to write the “Whole Fig Diet”.
But seriously, back to ancestral diets. Here’s what Dunn says about that:
And that eating some ancestral diet on its own will not make us healthy. Our ancestors did not eat diets perfectly in tune with their body. Rather, they took the best advantage of the foods around them they could in light of their bodies which, like ours, were whittled by evolution out of more ancient forms and so flawed, complicated, and filled with tradeoffs.
So, that’s the answer. Our bodies are what they are, thanks to millions of years of evolution. There is little you can do to your body with food (except for those damn figs, I suppose), so you take advantage of what food is available to you. You’re not going to live longer if you eat something or another. You’re not going to prevent or cure cancer. Don’t eat more than you burn is about the best advice you’re going to get. And eat more figs. So Cathy, there you go. Figs.
- Watts DP, Potts KB, Lwanga JS, Mitani JC. Diet of chimpanzees (Pan troglodytes schweinfurthii) at Ngogo, Kibale National Park, Uganda, 1. Diet composition and diversity. Am J Primatol. 2012 Feb;74(2):114-29. doi: 10.1002/ajp.21016. Epub 2011 Nov 22. PubMed PMID: 22109938.