Chapter 26 Chapter Twenty-Four

What is the difference between humans and animals?Humans have rational thinking.What kind of thinking do people use?Use the brain in your skull.In proportion to the torso, the human brain is surprisingly large, with a volume of 1,350 cubic centimeters and a weight of 1,500 grams, which is about 2% of the body weight.Most of us can consciously train and use our brains.But this is not to say that the size of the brain alone can determine the level of intelligence.A key prerequisite though is that at least our hard drives provide us with enough work and storage space. In the process of biological evolution, the body shape of animals has become larger and larger.An important reason may be that larger animals require less energy than smaller animals because of their relatively small surface area.However, as the body increases, the proportion of the brain to the body decreases.Compared with their body weight, the brains of the largest animals on land, such as elephants, cows, and horses, are pitifully small.Only the human brain not only grew simultaneously with the body during the evolution process, but also grew even faster than the latter.Our height has grown by a third in the past three million years, but our brains have tripled!We need only imagine that a two-year-old calf weighs about 200 kilograms and has a brain of only 350 grams.A two-year-old child weighs about 15 kilograms, and the brain weighs 1,000 to 1,200 grams.Judging by the ratio of brain to body weight, the child's brain was 60 times larger than that of a calf.

This is no accident.When the calf grows, it lacks long-chain highly unsaturated fatty acids, which are important materials for brain growth.What cattle ingest from feed are short-chain polyunsaturated fatty acids, most of which are digested by bacteria in the gastrointestinal system, leaving little left.Also, cattle have a limited ability to elongate them into long-chain highly unsaturated fatty acids.Therefore, cow's milk contains very little highly unsaturated fatty acids.Once the calf is out of milk and starts grazing on pasture, it has no ready nutrients and its own manufacturing capacity is limited.Due to this defect, the brains of ruminants such as cows cannot fully grow.

Compared with humans, the brains of our close relatives, the great apes, are also very different.The brains of chimpanzees and gorillas weigh about 300 and 400 grams respectively, and their brains account for 0.2% and 0.5% of body weight, respectively.Only dolphins are closer to humans. The dolphin's brain weighs about 1,600 grams, which is equivalent to 1% of its body weight.Therefore, among animals, dolphins are superior in intelligence.Every kid here knows from the TV series that even the cunningest guy can't fool the clever dolphin. Archaeological discoveries prove that our short ancestors were not more brainy than today's great apes.Through restoration calculations, the brain volume of the early Australopithecus living 3 million years ago was about 400 to 500 milliliters.2.3 million years ago, with the emergence of Homo habilis, the human torso grew and the brain began to grow rapidly, reaching its peak about 30,000 years ago. The brain volume of the Cro-Magnons reached 1,500 milliliters .

Compared with other creatures, why does the brain account for so much weight in the development and evolution of human beings?Paleoanthropologists have spent a long time trying to solve this puzzle. It was only in recent years that the details were assembled into a complete picture like a jigsaw puzzle: The scientists discovered the key clue when they compared the energy expenditure of the brains of humans and other mammals.They found that the human brain, which accounts for only 2 percent of body weight, consumes a quarter of the energy required to maintain all bodily functions at rest.From this, they concluded that our brains are metabolically active.

Other primate brains use only 8 to 9 percent of their resting energy requirements.Their brains had much less metabolic activity.The researchers unexpectedly found that although the human brain consumes such a large amount of calories, in terms of body weight ratio, the total calories consumed by the human body are no more than other primates. By now, one thing is clear.The human body compensates for the high calorie consumption of the brain by reducing the calorie consumption of other body tissues.The question is, which body part burns fewer calories?Through the corresponding physical calculations, the researchers quickly found important clues about the gastrointestinal system.The capacity of human gastrointestinal organs is only about 60% of that of apes of the same size.Today we can be sure that in the process of human evolution, the development of the brain was carried out simultaneously with the degeneration of the gastrointestinal system.The two factors influence and restrict each other, and both are indispensable.

In the process of developing into Homo sapiens, what force caused the degradation of the human digestive system?During the Ice Age, when food dwindled, if the intestines and stomach shrunk and their function declined, it would affect energy supply and even endanger survival.Instead, our ancestors got stronger and stronger.From this, it can be deduced that they must have a new food source, which is both more nutritious and easier to digest than the original food, so that the digestive organs gradually degenerated over hundreds of thousands of years. What is it that has so groundbreakingly improved the quality of human nutrition?At that time, our ancestors, like chimpanzees, ate more and more ripe fruit instead of green leaves and young stems.The fruit is easy to digest and absorb, and the fructose and glucose contained in it can also provide intensive energy.At the same time, due to climate change, the vegetation is decreasing.Cold-resistant plant varieties with special mutant genes did not yet exist.Therefore, it can only be animal food that provides such high-quality nutrition for humans.

There is no doubt that in order to survive and reproduce, our ancestors added more and more animal foods to their diet out of helplessness.But at that time, where was there ready-made fatty meat?Although insects and small animals are everywhere, there is not much meat on their bodies, let alone fat.At that time, Australopithecus had not yet mastered the use of weapons to hunt, and it was impossible to catch large animals that ran fast with just two hands.Fat prey can only be viewed from a distance. Sometimes our ancestors found injured, trapped or dead animals while foraging in the bushes.Every discovery like this means a big meal, because what is usually found are basically animal carcasses left over from being eaten by ferocious beasts.At this time, you have to be extra careful, because the hyenas, which compete with the australopithecus for food, are sometimes very dangerous.Besides, most of these corpses are leftovers, and the large pieces of meat must have been eaten long ago.Research from Tanzania's Serengeti National Park has shown that there is often no scraping of flesh from such wrecks.The unearthed fossils also prove that about 2.3 million years ago, the late Australopithecus and our direct ancestor Homo habilis had been able to use sharp stone tools to scrape meat from the animal bones they found.

It finally occurred to our ancestors one day that there was at least something edible in the remaining bones and skulls of the remains of these mighty creatures.Investigations from Serengeti have shown that, to this day, the only edible items left in the remains of animals abandoned by the beasts are brains and bone marrow.One of our ancestors finally discovered that with a heavy stone, the hardest skull and the strongest bone can be easily cracked open, and the delicious food inside can be enjoyed.A new food source was thus discovered, and fossils unearthed show that around the same time, the brains of our ancestors began to grow rapidly.Is this just a coincidence?

What does it take for physical and mental health to thrive?Requires energy, nutrients and a vibrant social environment.Humans have built complex social structures through hunting and gathering lifestyles.The most primitive social division of labor was formed, with women in charge of gathering and men in charge of hunting.Distributing the rare prey meat that everyone loves to eat to tribe members in the campsite is perhaps the most important social activity of that era.With population growth and the threat of food scarcity, this activity intensifies, increasing the pressures of survival, accelerating the development of the brain and intellect.

In order to expand the foundation of the brain, human beings need sufficient material materials and energy-dense food sources, so that they don’t have to eat piles of calorie-poor plants to obtain energy, and free themselves from this passivity and pressure. Let’s talk about material first.Although most of the brain is made up of water, 10% of the cellular material is protein and 10% is specific fatty acids, and it is these fatty acids that give the brain its distinctive properties.Unlike other tissues in the human body, the brain is dominated by long-chain highly unsaturated fatty acids (HUFA) with 20 and 21 carbon atoms, that is, arachidonic acid and docosane four in the Omega︱hexa fatty acid family enoic acid, and docosahexaenoic acid in the Omega|tri-fatty acid family.Like all other mammals, the proportion of Omea|6 and Omega|3 highly unsaturated fatty acids in the human brain is equal.This is how the brain differs from other bodily tissues.

In today's human diet, there is very little docosahexaenoic acid or other long-chain omega|tri fatty acids compared to omega|6 fatty acids.If the ratio of Omega︱6 and Omega︱3 highly unsaturated fatty acids in the brain is still 1:1, it means that the latter is densely present in the brain.The truth is that the brain can only fully develop if the ratio of these two long-chain fatty acids is equal. As we saw in Chapter 16, it is very difficult to convert the short-chain fatty acids contained in vegetable fats into highly unsaturated fatty acids.So if you want to have a large brain volume, you must take in enough ready-made fatty acids through food.Plants contain almost no highly unsaturated fatty acids, and only meat, offal, and various other animal foods contain these essential materials for brain growth.Therefore, strict vegetarians can hardly absorb these substances at all.In the previous chapter, we talked about the problem of the underdevelopment of the central nervous system in the offspring of strict vegetarians.It is no accident that herbivores have much smaller brains than the carnivores that prey on them, since carnivores are able to obtain an abundance of highly unsaturated fatty acids directly from their food.As a result, herbivores are far mentally inferior to carnivores because they cannot ingest and manufacture enough of the raw materials needed for brain growth. Let’s go back to the evolution of the brain.Active mutual communication in group life provides favorable external conditions for the development of the brain, and our ancestors obtained the raw materials needed for brain growth by eating animal food, especially the brain.Now they just need an energy-rich food that is easy to digest and assimilate to relieve the burden on the digestive organs and use the saved energy to maintain the expanding and increasingly active brain function. What are the possibilities?The muscles of prey are not often eaten, and the muscles of wild animals contain very little fat, with an average of only 110 kilocalories per 100 grams. From today's point of view, it is not the most important source of energy source.In addition, although the meat of wild animals contains some highly unsaturated Omega | three fatty acids, but not much.The brains of animals only contain 10% fat, which only provides 130 kcal of heat per 100 grams, which cannot be the calorie bomb we are looking for.The same is true of fish, and fish, moreover, entered the human diet much later.Although the fish in lakes in eastern Africa can provide rich Omega︱3 and Omega︱6 fatty acids, they are still not fat enough in general. They provide 20 kcal of heat per 100 grams, which is not a must. . Ordinary plant foods are not energy-dense enough (an average of 30 kilocalories per 100 grams), let alone ranked.Only nuts and some plant seeds contain 29 grams of fat per 100 grams, providing 310 kilocalories, which can meet the high calorie needs.But nuts, like all vegetable fats, do not contain highly unsaturated fatty acids.Therefore, it is impossible for this type of food to promote the development of the brain and the degeneration of the stomach. Let me tell you the answer: bone marrow was the only food source that was abundant at the time and that provided a fairly high density of energy.The bone marrow of every 100 grams of African ruminants contains 84 grams of fat, which is basically monounsaturated fatty acids and can provide 790 kcal of heat.This is the energy bomb we were looking for. At that time, it was everywhere in the wilderness and could be found every day.However, there is a paradox that bone marrow does not contain highly unsaturated fatty acids. In fact, no single food meets all scientific research requirements at the same time.Human brains did grow abnormally during evolution, so our ancestors must have created an ideal pairing: where animal bones were found, prey skulls must be not far away, and bones and skulls could be used The same tool breaks open.Did our ancestors have a better choice than eating the contents of both things together?This is how they get a lot of energy that is easy to absorb, and it is in the form of monounsaturated fatty acids, like olive oil in the bones, as well as sufficient brain-building materials, and a balanced mix to get the best ratio of 1:1 Omaga︱6 and Omega︱three highly unsaturated fatty acids. By extracting these nutrients from prey and animal remains, our ancestors created the prerequisites for the atrophy of the digestive organs, which in turn released stored energy to feed a growing, increasingly active brain.From mainly plant food to animal food, this transition has become a decisive factor in the development of intelligent animals in the process of human head evolution.I think if there is no mad cow disease, everyone should eat more brains. Since the introduction of agricultural life at the end of the Stone Age, the human brain has shrunk in size.The current average human brain volume is 1,350 cubic centimeters, about 11% smaller than that of our ancestors who lived 30,000 years ago.If we pursue the reasons, the first problem we encounter is the supply of the material materials that make up the brain.When humans can still take in enough long-chain Omega︱3 fatty acids from the meat and internal organs of a large number of wild animals, the supply of docosahexaenoic acid is about 80 mg per day.Since the introduction of agricultural life, human consumption of grains has increased rapidly, and later starch-rich tubers have been eaten more and more, while food sources of highly unsaturated fatty acids such as meat, offal and fish have gradually been squeezed out of human consumption. diet. Furthermore, vegetarianism authorities claim that world hunger can only be solved by reducing the consumption of meat and other animal foods.They call for eating more grains and soybeans, which means more Omega︱6 fatty acids, which means less long-chain Omega︱3 fatty acids.The results of the survey of babies born to vegetarian mothers did not seem to shock them.Apparently, they want our brains to keep shrinking.Could it be that vegetarianism, which is a combination of arbitrary and blind obedience, can also damage people's intelligence?