More than 2 billion people worldwide are now overweight, and chronic health disorders such as colon cancer, cardiovascular disease, obesity, and acne vulgaris are highly prevalent in many parts of the world. Few people stay lean and free from chronic diseases their entire lives, and it seems that dying of old age has gotten old. Why is it so? Are disease and fat accumulation just a natural part of human life? The typical approach that is used to answer these questions is to study the diseases itself, largely as a means to develop drugs, cures, supplements, and vaccines, which are often touted as the solutions to our health problems. While this approach has its merits when used in the right situations, I don’t think this is where the primary focus should be. Rather, I believe that to understand why we are so sick today, we have to turn the clock back millions of years to where it all began for our species: Africa.
As you know if you’ve been reading this blog for a while, I think evolution should be the guide in all matters of health and fitness. By narrowly focusing on the modern era we’re grasping in the dark, but if we look to the past, we can establish the basic facts we need to make sense of complicated questions, ideas, and hypotheses.
In this series of posts I’ll take a look at how our species evolved and briefly discuss what evolution can teach us about health, fitness, and human adaptability. Human evolution is clearly a vast subject that is impossible to cover in-depth in a couple of articles, so what I’ve done is to boil things down to some of the most essential concepts. If you want more details on these topics, check out some of my previous articles on the subject, such as the one where I take a closer look at the evolution of the human diet.
I want to emphasise that although there’s a lot we know about the origins and evolution of the human species, there are also many unanswered questions and a lot of debate as to how our evolutionary road really looks like. So, although I’ll stick to the things that are fairly well established, it’s clearly possible that future findings will shed a different light on certain aspects of our evolutionary path. However, the important thing is to understand the grand scheme of things; the exact dates and details aren’t that relevant.
Life as a Stone Ager
Imagine for a second that you’re back in stone age times living as a hunter-gatherer in East Africa. All comforts of modern life are gone, and the sounds of driving cars are replaced by the singing of birds and the sound of running water nearby. Your alarm clock, desk job, and computer are all but a distant memory, and a new hunter-gatherer existence has taken its place…
Would you have swapped out your modern life for a life as a hunter-gatherer in the Paleolithic? Most likely no. However, I think we all can agree that there is something beautiful and raw about a Paleolithic way of life. Also, there is no doubt that we can learn a lot from studying the diet and lifestyle of ancient humans. As you know if you’ve followed this blog, the data suggest that although most of us would look at a modern man and say that he is very different from a primitive, ancient hunter-gatherer, the fact is that our genetic blueprint is still largely the same as that of our late Paleolithic ancestors’.
Our species, Homo sapiens sapiens, which I’ll refer to as Homo sapiens from now on, emerges in the fossil record approximately 200.000 years ago. Clearly, our genus, Homo, has been around for much longer than that, and if we really start to dig back into our evolutionary history, we know that all life on earth descends from a common ancestor that lived billions of years ago. However, to not make this story too long and tedious, we’ll focus on our own species.
To really understand how anatomically modern humans came to be, we have to take a look at the adaptations that evolved during the millions of years it took to make the transition from tree-dwelling primates into standing, walking, and talking humans.
A bipedal and sweaty man
How did the features that characterize the human body evolve, and what is it that differentiates us from chimpanzees and gorillas? There are many things of course, but some traits are especially important. First of all, we walk on two legs. You might not have given it any thought, but habitual bipedalism is relatively unusual in the animal kingdom. In combination with longer legs and large, powerful glutes, bipedalism is largely what made it possible for humans to become such good long-distance runners/walkers.
Another thing that really sets us apart from other primates is our lack of fur. While many modern humans look at sweat as a greasy, inconvenient, and unappealing liquid that run down the back of those fatigued people at the spinning class, the fact is that we wouldn’t have been where we are today without our ability to perspirate as we do. Because how could the Paleolithic man really be able to hunt effectively? Humans are neither strong nor fast compared to many of the animals we went after when we lived as hunter-gatherers. While many game animals can use speed to their advantage, our ancient ancestors had to depend on their ability to move long distances without getting fatigued. In the hot midday sun, an ability to cool down through perspiration gave Homo sapiens an advantage over other animals that basically had to give in from heat stroke after hours of being chased.
Well, you might say, how do we know that this is the way early humans hunted? It’s true that we can’t know for sure how our ancient ancestors got their hands on calorie-dense animal foods. However, looking at contemporary hunter-gatherers can give us many clues. Studies investigating the life of Kalahari bushmen in Africa show that these isolated humans kill large animals by hunting for many hours during the hottest parts of the day (1).
People who have spent time living with, and hunting with, indigenous tribes have reported that hunter-gatherers possess fitness levels that are far superior to most active westerners (2). That’s not to say that all forager tribes get a lot of their food from hunting, or that plant foods aren’t an essential component of many ancestral diets. However, there’s little doubt that hunting and scavenging were a component of our ancient ancestors’ subsistence mode (3, 4).
So our ability to run long distances during the day without overheating certainly played an important role in our transition from tree-dwelling primates into anatomically modern humans. Also, as an interesting sidenote, this evolutionary perspective can help explain why men usually sweat more than women…
Larger brains and smaller guts
In the discussion of human evolution, our large brain is of course an important feature to mention. How did we evolve such massive brains? Nutrition had to have played a significant role, primarily because having a large brain is very costly from an energetic standpoint. The brain burns through calories like nothing else, and in a Paleolithic environment it would have been impossible to fuel a large brain by eating exclusively plants. Actually, in an ancestral, natural environment, vegetarianism would have been an unnatural – and deadly – behaviour for Homo sapiens, a statement that is supported by subsistence data which show that all hunter-gatherer populations eat some type of animal source food (4).
The introduction of more meat (and possibly also honey and tubers) into the hominin diet was also a driving force behind the evolution of the human gut, with a reduction in the size of the colon being the most prominent change that followed from a transition to a higher quality diet.
Large plant eaters have complex digestive systems that allow them to extract energy from the complex carbohydrates they eat. Unlike meat, which is fairly easily digested by host enzymes, many of the carbohydrates in plants are broken down by bacteria in the gut. So, what many people don’t know is that cattle actually derive most of their energy from fatty acids produced during the breakdown of the plant material they eat. In other words, the cow you see grazing at your local farm is actually eating a high-fat diet.
The African environment
Some researchers have suggested that the environmental conditions in Africa during the late Paleolithic were rapidly changing between periods of extreme heat/drought and rainier periods. Exactly how extreme these environmental shifts were, we will never know, but the dynamic nature of this early human environment can be one of the first clues as to why Homo sapiens is such an adaptable species.
In terms of diet, we know that Paleolithic humans who lived in Africa were omnivores, with a diet consisting of varying amounts of tubers, fruits, and certain other wild plant foods, as well as animal source food (3, 5). But do we have a more detailed documentation of the African Paleolithic diet? Our Paleolithic ancestors clearly didn’t keep a food journal, and there’s really only so much you can gather from studying ancient fossils and dental remains. However, we do have a fairly good understanding of what early humans ate (which I won’t go into in detail here), and we also have access to data from contemporary hunter-gatherers who live in an environment that is thought to closely resemble that of our African ancestors. Although clearly not a 100% accurate representation of a Paleolithic diet, the diet of hunter-gatherers such as The Hadza (Tanzania) gives us a good window into what might have been on the menu in Paleolithic times.
So, what do contemporary african hunter-gatherer populations such as The Hadza eat? Their diet fluctuates over the year, something that is to be expected when you live in an environment where climatic conditions and food availability are far from constant. In general, the Hadza diet consists primarily of meat, honey, berries, and tubers, all foods that the literature suggests were an important part of the diet in the Paleolithic as well.
The primary takeway from this post is that we should keep in mind that human biology and physiology were shaped through millions of years of evolution in Africa. In the next post in this series I’ll take a look at what happened as we travelled out of Africa, and I’ll discuss how this evolutionary perspective can help us understand why we are so sick in today’s world.
Picture: Creative Commons Picture by Ian Sewell. Some rights reserved.