Dust, heat, a waiting crowd, two boys whipping each other’s backs with whips. This is what the initiation ceremony looks like for the Fulani people, who live in a vast territory in West Africa. There are variations in the rite of passage from village to village, but the essence is the same everywhere: prove that you are a man through your patience and fortitude. In 2015, scientists found traces of this cruel custom in the DNA of members of the Fulani tribe: their genes encoding taste receptor proteins underwent mutations that reduced the sensitivity of the receptors. It turns out that shortly before the initiation, boys are given palm beer to drink, which tastes so awful that it can only be tolerated after several years of persistent training and with a dulled sense of taste. Otherwise, you cannot drink this swill, and without it, it is impossible to endure the cruel blows. Therefore, over the centuries, evolution has selected men from the Fulani tribe with mutations in the TAS2R gene, allowing them to process the alkaloids in palm beer more efficiently and thus facilitating their initiation into adulthood. The rest simply could not withstand the blows of the whip: the shame of a ‘failed’ initiation prevented them from marrying and, consequently, from leaving offspring. The most insensitive will survive. ‘The story of the Fulani is very vivid and illustrative,’ says Tatiana Tatarinova. ‘The taste genes of modern humans not only vary from people to people, but also differ from those of Denisovans and Neanderthals. For example, today we all like the smell of smoked sausage, but ancient people might have found it completely uninteresting.’

Our brain is a very demanding organ. It accounts for only 2% of our total body weight, but consumes up to 20% of all the energy in the human body: the high-performance calculations that once enabled humans to communicate, plan their actions and make complex tools require a great deal of energy. Therefore, any innovation that made it possible to extract energy from food more efficiently made humans not so much stronger, faster or bigger, but smarter: the excess energy was spent on the work of our main adaptive organ. The first and most grandiose gastronomic revolution in human history is associated with the discovery of fire and is lost somewhere far back in the centuries. Scientists still argue about how it all happened. Some believe that humans first developed mutations that allowed them to digest roasted and boiled food without being poisoned by the by-products of such heat treatment. These lucky ones were able to cook the first prehistoric steaks and meatballs using forest fires or the heat of hot springs, gaining a substantial calorie boost, which they then used to develop their brains, which in time allowed them to master the art of fire. According to another version, ancient humans first learned to light and maintain fires in their caves for warmth, and only later did the luckiest among them — those with the right genes — gradually begin to cook food and gain an incredible evolutionary advantage from it, which gave them the resources to carry and give birth to more children and populate the territory with their descendants. The domestication of fire in the ancient world was no surprise: Neanderthals, Denisovans and, apparently, even Homo ergaster knew how to cook food, but agriculture was only possible for Homo sapiens and forever changed our DNA. A recent study by American scientists has shown that modern humans have an average of six copies of the AMY1 gene, which encodes the enzyme amylase, while Denisovans and Neanderthals have only two diploid copies. Salivary amylase hydrolyses starch and glycogen in the oral cavity. ‘Apparently, when humans developed agriculture, they gradually developed a completely different reaction to starch than other hominids. Neanderthals and Denisovans could not digest wheat or rice as efficiently,’ says Tatarinova. Humans are the only mammals capable of consuming dairy products in adulthood, after transitioning to solid food. Others can only drink milk in childhood, and then the genes responsible for processing lactose are switched off so that grown offspring do not follow their mothers around for the rest of their lives and she can feed new offspring. The same thing used to happen with humans, but then they domesticated cows, goats and sheep, and so, gradually, humanity became accustomed to consuming milk. ‘According to anthropological data, cows were domesticated about 10,000 years ago, and the genes for processing milk appeared about 5,000 years ago,’ says Tatarinova. ‘For 5,000 years, people kept cows, produced and ate cheese, but could not drink whole milk.’ It is not difficult to explain this time lag. After all, each gene can exist in several variants, or, as scientists say, in ‘alleles.’ All cells in the human body, except for sex cells, contain two alleles of each gene — they carry two sets of chromosomes. If these alleles differ and contain different instructions for synthesising the same protein, the body will follow only one of these instructions — the dominant one. For example, a person with two alleles of the gene that determines eye colour — blue and brown — will have brown eyes because the brown eye allele is dominant and the blue allele is recessive (this is a simplified description of a case of complete dominance. In reality, the body may try to follow both instructions at once, and the eyes will be green — this case is called incomplete dominance). Therefore, even the most beneficial genetic innovation in humans cannot take hold quickly. First, a mutant allele must randomly appear in several people, the action of which will most likely be suppressed by other, dominant variants of the gene. Then two ‘mutants’ must meet and produce offspring that will have two copies of the new allele. These offspring must grow up, survive and reproduce, and so on. It takes a total of 150–400 generations (or 3–8 thousand years) for a new trait to become established in our DNA, and that is if it gives its carriers significant advantages in everyday life. This is precisely why lactose enzyme genes have been so slow to take over the world: genetic research on 13 skeletons found on the Great Hungarian Plain and dated to 5700–800 BC showed that all of the individuals found were lactose intolerant. Incidentally, this trait is still present in more than half of the world’s population. Only people living in northern countries, including Russia, can drink milk and break down lactose: here, an unusual mutation that appeared several thousand years ago was particularly beneficial. In conditions of a meagre diet and a lack of sunlight, dairy products became a key source of energy and micronutrients necessary for life and the birth of healthy offspring. Incidentally, a recent study in the journal Nature Genetics showed that there is a significant correlation between the increased genetic diversity of milk genes in cows, the geographical areas of Neolithic settlements with cattle, and the current level of lactose tolerance in Europe. So it seems that it is no coincidence that the Dutch have the most delicious cheese! ‘In the genomes and eating habits of modern humans, we see factors that appeared 8,000 years ago during the transition to the Bronze Age,’ says Tatarinova.

In 1994, researchers from Brigham Young University announced that they had obtained a fragment of mitochondrial DNA (mtDNA) from a Cretaceous-period dinosaur from bones that were 80 million years old. This was a sensation: humanity had been given the opportunity to glimpse into the genetic history of the prehistoric world. The reality turned out to be much less interesting: other laboratories were unable to replicate the results of this study, and the unique fragments of mtDNA found were more similar to human mtDNA than to that of birds or reptiles. Scientists realised that what they had taken for prehistoric antiquities were actually traces left by careless laboratory assistants working with the samples. Such stories often occur when working with ancient DNA (aDNA), not only from dinosaurs but also from humans. The words in genetic chronicles are erased, and the manuscripts themselves disintegrate into pages and are defaced by illiterate barbarians. Ancient DNA molecules gradually shorten under the action of bacterial enzymes that decompose fossil remains, spontaneously change their structure (for example, cytosine gradually turns into thymine over time) and mix with the DNA of the same bacteria or, for example, wolves that dug up graves to feast on bones. Alas, no information carrier on Earth is eternal. Therefore, scientists are very cautious about dDNA research, and the most ancient organism whose DNA has been sequenced is currently considered to be a horse from the Middle Pleistocene epoch, which lived somewhere between 560,000 and 780,000 years ago. Humanity has not yet ventured further into the genetic history of the world. However, it is necessary to be careful when working not only with very ancient DNA. ‘If you want to work with the remains of your great-great-grandfather who died in the Battle of Borodino, you need to have a Chinese or even African lab assistant on your team,’ says Tatarinova. ‘Even an experienced researcher can contaminate ancient samples with their own DNA, but traces of Africans or Chinese in European data will be easier to filter out based on specific mutations.’ In addition, careful analysis of the data will help distinguish ancient DNA from modern DNA, for example, by the characteristic conversion of cytosine to thymine, which by its nature most often occurs at the ends of DNA macromolecules — they are more actively involved in Brownian motion and are therefore more reactive. Careful study of ancient DNA must also be carried out on several SNPs (single nucleotide polymorphisms) at once and achieve good data reproducibility for different laboratories and different samples found in the same burial site or cemetery. Add to this the conditions of special ‘clean rooms’ for working with DNA and meticulous selection of bones. ‘Thick and dense bones are better suited for research, as bacteria from the environment have hardly penetrated deep into their tissues — the large tibia, temporal bone, and enamel-protected parts of the tooth,’ says Tatarinova. The result is a very costly and laborious experimental design, which is why there are still very few good studies of ancient human DNA — even finding several skeletons with suitable bones in a single burial site is not easy. Anthropologists help geneticists with their much more precise methods: for example, the diet of our prehistoric ancestors from an excavated site can be reconstructed based on the appearance of their teeth and the isotopic composition of their tissues. ‘Ancient DNA is full of junk, and when working with it, you have to constantly separate the wheat from the chaff,’ says Tatarinova. “Anthropology is a much more established science, so it makes sense to take anthropological hypotheses and test them using genetic data. Anthropological data can help to paint, figuratively speaking, a larger target for further genetic research. But if the arrow of ancient DNA hits a target on another tree, then most likely something is wrong with the genetic data.”

There is another, much simpler way to get a glimpse into the cuisine of our ancestors — not by digging into their ancient DNA, but by taking a closer look at the legacy, unique tastes and preferences they left behind for billions of modern people. For example, the diet of the Maasai, a semi-nomadic African people living in the savannahs of southern Kenya and northern Tanzania, seems strange to us at best and deadly at worst. ‘The Maasai can eat so much fat and not get fat that I, a European woman on a perpetual strict diet, just want to die of envy,’ says Tatarinova. ‘On average, they eat six times more fat per day than Europeans, and yet they remain thin.’ In 1971, scientists decided to test this unusual feature of the Maasai in an experiment. They assembled two groups of subjects aged 20-24, each of which included both Maasai and Europeans. The scientists kept the people in the control group on a normal diet, while the others were given two additional grams of cholesterol per day. After eight weeks of this diet, the Maasai felt absolutely no difference: the blood cholesterol levels of the Maasai in both groups were the same within the margin of error. The Europeans were much less fortunate: every additional 100 milligrams of cholesterol in the diet increased blood cholesterol levels by 11.8 mg/100 ml (with a normal range of 160-250 mg/100 ml). We can only guess how these two-month trials affected the lives and health of genetically unprepared Europeans, but one thing is certain: cholesterol is not a problem for the Maasai. Incidentally, this is why it is customary in their society to marry young girls to experienced 60- and 70-year-old men who are not overweight, do not have cardiovascular problems and, most importantly, are fully capable of producing healthy offspring. Many centuries of natural selection have left only the most adaptable Masai — those who can eat fatty foods without developing serious heart and vascular problems. Scientists recently found a story similar to that of the Maasai or Fulani in the genes of the Greenland Eskimos, whom they compared with some peoples of India, South Asia and Africa who have historically adhered to a vegetarian diet. Scientists tracked the frequency of an allele associated with adaptation to food in the context of omega-3 and omega-6, unsaturated fatty acids necessary for the functioning of the human body, which humans can obtain almost exclusively from food. It turned out that the genes of vegetarians have been honed over centuries to intensively process food in order to extract deficient omega-3 and omega-6 from plant foods, while Eskimos, with their marine diet rich in saturated fatty acids, do not have such mutations. Being a vegetarian is almost impossible for them. Milk, cholesterol, saturated fatty acids, alcohol — our gastronomic preferences are fixed in the genes and traditions of distant and close ancestors. A careful look at DNA will help to select the optimal diet for each person in the future. Nutrigeneticists do not yet have a complete picture of the relationship between genes and nutrition, and new research in this area is not easy to conduct. Experiments on modern humans similar to those conducted on the Maasai would not be approved by ethics committees, as one group of people would be guaranteed to receive harmful nutrition (like those Europeans fed cholesterol). Alternatives — research on ancient DNA — are still very complex and expensive. ‘The cost of sequencing ancient DNA is much higher than that of modern DNA,’ says Tatarinova. ‘Currently, such work in different countries is funded exclusively by fundamental research agencies — there is little private investment. But I think that commercial companies will soon enter this field, as recreating the genetic picture of the evolution of eating habits could significantly influence the food industry.’ Moreover, food affects not only our genome, consolidating the necessary mutations in it over thousands of years, but also our epigenome: any food we eat changes the activity of our genes almost in real time. Source