Chapter 2: Searching for the ancestral diet
Here is the extract and my notes to the Chapter 2 of Gary Nabhan book: Why some like it hot.
It is for sure that our modern diet is vastly different from what our ancestors ate. Our food is spiked with all sorts of additives, preservatives, altered molecules (trans-fats from previously normal cis formed plant oils) and others. We are also more conscious about what we are eating and a whole diet industry has evolved, based on food and its function. There are armies of famous chefs or food doctors who aim to fix whatever problem people have in relation to food and to make people beautiful, slim and fit in addition to bringing them eternal youth and health. However, hardly any of these approaches take into account the uniqueness of genetic make-up of anyone of us. And there you have people who swear on high-carb low-fat diet, while their opponents promise you a great health with exactly the opposite.
What do we know about Paleo ancestors?
The chapter continues with some remarks about the Paleo diet and how our physiology is still in the Stone Age when people did not consume grains but the majority of their calories came from animal sources. Scholars announce that some 500 generations back, which means about 2.5 million years ago all people on Earth ate the same way and saying
“This diet has been built into our genes”.
And millions of people follow this diet and report positive changes in health.
Since the old times the humankind has diverged from the common ancestor. Various cuisines emerged and although in the more recent past there were quite clear boundaries between these cuisines, in the modern globalized world this is not true anymore for most of us. One day we have Indian meal, the other day Chinese meal, the pudding does not match the cultural origin of the meal it follows, etc. And our genome has also mixed quite well over the centuries and millennia and across the continents. So even if the genetics of some cultures had adapted to their particular cuisine during the past centuries or millennia, it is no longer so simple. Gary mentions, that
“Seven million Americans identify themselves as composition of two or more races”.
And, as I have learned just recently, humans now differ in their salivary amylase gene, which makes some people more effective in utilizing glucose from starch than others, and those less capable of doing so respond with higher concentration of glucose after eating starch. This was hypothesized as making these less efficient individuals more prone to metabolic consequences due to enhanced glycation or insulin resistance. This suggests we are not so similar to our ancestors from Paleolithic era as many think, or, at least, not all of us are. Gary expressed it this way:
“Hundreds of thousands of dieters have chosen to do just this, pledging to spend their budgets on calories, cures, luncheons, and literature that pursue a Paleolithic prescription, one that ignores ethnicity in exchange for a sense of antiquity. They have become hooked on Website versions of an ancient cuisine variously referred to as the Cave Man Diet, the NeanderThinTM formula, the Origins Diet, the Stone Age Menu, the Paleo Diet, or the Carnivore Connection.”
The science, however, whether based on paleonutritional, zooarchaeological or ethnobotanical studies, does not suggest that people following the Paleo diet are copying the ancestors. However, what Gary summarized, was:
- As much as 65% of the energy of hunter-gatherers came from vertebrates, eating all parts, including of fish, but seldom eggs. Never consumed milk products.
- What they found was consumed in raw form: fruits, flowers, leaves, bulbs and these were richer in phyto-compounds, having a potential to prevent diseases, than ‘most of our cultivated food crops’.
- Rarely they consumed cereals and definitely they did not grind them into white flour.
- Their diet was rich in calcium and potassium salts, but low in sodium salts.
- The ancestors rarely camped and therefore could not consume fermented fruits or other plant sources used for making alcohol today. They did not even know vinegar.
And he continues: “… – we must gain some sense of whether there was ever much place-specific variation in dietary preferences.”
Variety worldwide but also within tiny distances
Hominids have been evolving simultaneously on different places of Earth over time and it is likely that their diets varied, depending on their habitat and other factors:
“… most characterisations of ancestral diets woefully simplify such variation, ignoring incredible levels of dietary diversity that have guided our evolution in space and in time.”
The chapter continues with the history and personal experience of Gary with isles of Java, Bali, Lombagan and Lombok, talking about Java Man and his potential diet, how it may have changed as he moved from one place to another, because Indonesia is so varied in flora, fauna and the landscape. There he witness dramatic changes in environment, including fauna and flora, within 10 miles of distance and thought how this once affected the diet of a prehistoric man when he managed to cross the water and move from one island to another. Lombagan and Penida islands are generally hot and arid, populated with shrubs and aromatic or terpenes rich plants, in contrast to Bali which is moist and full of vegetation, providing shade under the green canopy. The isolation of the isles has even affected the species of birds, which should be able to fly from one island to another without difficulties. Yet Java and Bali share some 97% of birds species, the Lombok, which is just ‘two dozen miles south’ had only 50% of the birds species in common with Bali.
This variety can be seen on the larger scale, too. Just remember how awkward animals live in Australia and compare it with Island. Compare some tribes from Africa, of which the diet is dominated by starchy staples to the Inuits, the diet of which is almost entirely comprised of animal sources, rarely having something of plant origin. People followed their diet and lifestyle for hundreds and thousands of years, slowly adapting to what they managed to find or hunt for food. Can we still say that we all have the same genes as our ancestors and therefore we should eat all the same way?
Every new generation is different – a bit
“Wallace demonstrated that there are hugely different selection pressures placed on plants and animals inhabiting distinctive landscapes just a few miles apart. Because such populations exist in some degree of reproductive isolation from one another, a second evolutionary mechanism favoring divergence, genetic drift, is also active.”
This genetic drift refers to changes in the “frequencies of genes in population that becomes more pronounced the smaller and more isolated those populations happen to be”. So, if a gene for any different trait is suddenly introduced to the small and isolated community, there is a chance it will become dominant over time. The same happens for the flora and fauna on isolated landscapes, expressing a sort of skeweness in comparison to the mainland with a larger variety of everything. It has even got a name: adaptive radiation. And now you know that the distances between the isolated ecosystems do not have to be too large.
Wallace did in Indonesia what Darwin did in Galapagos. But while Darwin worked systematically on his work over decades and hesitated to come out with his work in the creationists dominating world, Wallace was rather intuitive and progressing more quickly. Wallace was the reason why Darwin finally published his work – to avoid being the second.
Nonetheless, although Darwin and Wallace initially thought that this genetic drift occurs over a long time due to the accumulation of changes, the truth is otherwise. As little as one new generation can provide evidence of change, mostly driven by the changes in the environment. This was demonstrated on the size of finch beaks on Galapagos in response to the size of the seeds they managed to consume. I remember reading about this several years ago: the drought had caused poor supply of the usually (rather small) sized seeds and the finches with small beaks could not feed on what was (rather not) available to thrive. However, those that had larger beaks due to a genetic trait and could feed on small or larger seeds, were able to breed successfully on what was left and available, forwarding their ‘larger beak genes further’. The next generation of finches was typical for a higher frequency of larger beaks among the population. Should this drought repeat for several more years, the finches with small beaks could face extinction.
However, this is still within the natural selection theory (now considered as fact) based on that the gene was already present. How about the introduction of a completely new gene to the new generation, making it so different from the previous one?
Indeed, Gary summarized that our physiology was not definitively profiled 2.5 million years ago with the emergence of Homo genus, nor 200 000 years ago in East Africa as assumed from the ‘mitochondrial Eve’. Instead:
“They have been constantly reshaped by the peculiar range of food choices, environmental stresses, diseases that humans face in every place in which they have spent considerable time, and, of course, our reactions continue to be reshaped by our present food choices and disease exposures as well.”
Gary further continues:
“Human populations like our own have encountered distinctive sets of foodstuffs and dietary chemicals that interact with our genes, wherever we have lived.”.
“Each time I have visited with archaeologists who sift through the soil at early hominid camps, they seem less certain that there is a single discernible dietary pattern evident among excavated sites. Some scholars have begun to doubt whether Java Man or other populations of Homo ever kept to a uniform diet; some even wonder if ancestral diets contained more or less the same proportions of fats, proteins, sugars and fiber.”
This only agrees with my concerns about the distant development of physiology and metabolism between Africans and Inuits I mentioned earlier. Gary confirmed my concerns by describing human diversity in terms of “genetic variation within our species interacting with the diversity of edible plants and animals distributed across this planed in ways we are just beginning to understand.”
This suggests that “there may not be an optimal diet for all humans, past and present”. And, finally:
“One explanation may be that we differ genetically from one another in small but significant ways that not only shape our food preferences, but that are reciprocally shaped by them.”
What is more, the genetic difference between people cannot be judged by appearance, as per skin color or the shape of nose. In fact, there is more genetic heterogeneity within a particular ‘race’ or ethnicity than between them. That means the supposedly 99.9% of the genes shared among human population and even with the ancestors some 100 generations ago is not quite correct because the geneticists calculated that there is 7-15 % heterogeneity between various ethnics and now you know that within ethnics this is even more. This was confirmed among primates who were found to vary in their genes considerably, even within the same species but living less than 100 miles from each other. Those 99.9% were explained as within the 3 billions of nucleotides we have in our DNA, one in thousand is different among individuals. That gives about three million nucleotides potentially differing between people – now that is impressive. What is more, a single mutation in the chain of nucleotides can result in a faulty protein, causing life threatening disease.
And now put it into a perspective of 200 000 years. How genetically similar we are to Lucy or any other ancestor when we today vary so much from each other? We certainly have two legs, two arms, grow hair on head and consume food which has to be chewed and acted upon by our enzymes. But what about the diet composition? Since we now know how varied diet of our ancestors was; that one tribe have had different diet than another tribe, can we say today that one size fits all in terms of dietary patterns?
Did all hunter-gatherers share the same dietary patterns?
Earlier in this article I referred to 65% of energy consumed from animal sources among ancient hunter gatherers. However, as Gary mentioned, of some 229 hunter-gatherer societies living today, one in seven clearly consume more plants than animal foods. Add the variations due to seasons, habitats, cultures and you have an answer on the question in bold above. And that was also published in the American Journal of Clinical Nutrition in 2000 by Loren Cordain et al. Moreover, this dietary diversity applies not only on the macronutrients, such as proteins or carbohydrates, it also applies on non-nutritive compounds, of which many are able to either poison us or prevent various diseases. And the presence of these copounds vary from place to place or in different altitudes of the same land together with the diversity of fauna. Unfortunately, many of these compounds have been bred-off the modern crops, often due to better palatability of the cultivated produce.
Although these secondary compounds do not have apparent role for our metabolism, those that were found in “wild foods are potent enough to cause our own genes to mutate”. Therefore, these plant chemicals played a significant role in the genetic diversity of various human societies who consumed them. Some of these plant chemicals were given name allelochemicals – compounds able to modify behavior of predators or competition in order to protect the plant itself. This does not only apply to the expression of genes, which can easily be switched on or off by various food compounds, but the original DNA as well! So it is no longer true that we are guaranteed to die with the same DNA we were born with. Period. It appears that:
“dietary chemicals are major driving forces for genetic expression, mutation, and selection within our species,…”
Overall, Gary referred to Strassman, an author of different materials, that he warns from the view that our nutritional needs were “set” in the Paleolithic era. This view “ignores the fact that human evolution has been mosaic in form; different components of our biology evolved at different stages and dates…”
Gary further says:
“The coevolutionary dance between our genes and our foods began long before the first farmers and herdsmen and continues to this day. The list of gene-food interactions … have been documented for some ethnic populations but not others, making the notion of a single optimal diet for all of humankind an absurdity.”
Although this is the end of my chapter, in the book there is more fascinating reading about the interaction between specific plant compounds and our physiology. Because I do not want to spoil the original work of the author too much I rather end my writing here. Please check other chapters and enjoy their content.
Chapter 2: Searching for the ancestral diet
Chapter 5: Discovering why some (don’t) like it hot
Chapter 6: Should we change places, diets or genes?
Chapter 7: Rooting out the causes of disease