Researchers propose that a fermented morsel of flavor may have caused an astonishing increase in the growth rate of our ancestors’ brains.
In fact, the transition from a raw diet to a diet containing foods already partially broken down by microbes may have been an important event in the evolution of our brains. According to a perspective investigation by Catherine Bryant, an evolutionary neuroscientist at the University of Aix-Marseille in France, and two colleagues in the United States.
Over the past two million years of evolution, the human brain has tripled in size, while the human colon has shrunk by an estimated 74%. This suggests that the body has a reduced need to break down plant-based foods.
Although we know the timeline and extent of human brain expansion, Mechanisms that allow energy directionality This extension is more complex and somewhat controversial.
Study authors layout Their “external fermentation hypothesis” points to a metabolic landscape in our ancestors for selective brain expansion, which may have been set in motion by transferring intestinal fermentation to external processes, and perhaps through experimentation. may even have been done. It also includes preserved foods similar to wine, kimchi, yogurt, sauerkraut, and other pickled foods that we still eat..
The human gut microbiome acts like an internal fermentation machine, increasing the absorption of nutrients during digestion. organic compounds ferment Enzymes convert it into alcohol and acid. Enzymes are usually produced by bacteria and yeast that live in parts of the digestive system, such as the colon.
Fermentation is an anaerobic process and does not require oxygen, so fermentation can occur in closed containers as well as processes in the intestines. This process produces energy in the following ways: adenosine triphosphate (ATP), which is an essential chemical energy source that fuels our metabolism.
The researchers argue that culturally inherited ways of handling and preserving food may have facilitated the externalization of this function.
Externally fermented foods are easier to digest and contain more available nutrients than raw foods. Additionally, there is less for the colon to do if the food has already been fermented, so the organ may shrink in size over time, potentially leaving energy available for brain growth.
The brain size of our ancestors was Australopiswas similar to that of chimpanzees (pan-troglodytes) and bonobo (Pan Pan Niscus).The expansion of the human brain has accelerated homoemergence and continuation of homo sapiens and homo neanderthalensis.
How were our ancestors with brains the size of chimpanzees able to harness the power of external fermentation?
Bryant and her team found that hominids with lower cognitive abilities and smaller brains were more susceptible to hunting animals and cooking them with fire than alternative explanations that have been proposed for redirecting energy from the gut to the brain. They suggest that they may have adapted to fermentation much earlier.
![Comparison of expected and actual organ size](https://www.sciencealert.com/images/2023/11/FermentationHypotheisisHumanOrganProportions.jpg)
Fermentation has many benefits associated with cooked foods, including softening texture, increasing calorie content, improving nutrient absorption, and protection from harmful microorganisms.
All you need is a simple storage space, such as a cavity, cave, or even a hole in the ground, and it’s basically your ticket to easy entry, stress-free, and superior nutrition. As the researchers point out, “Planning and tool use are not necessary and can trip you up.
“Hunting, scavenging from large carnivores, and using fire all come with risks.” Bryant and colleagues write“Perhaps the risks of fermentation are more predictable and therefore more reliably mitigating through individual and cultural learning.”
In addition to increasing the bioavailability of nutrients, external fermentation can also make toxic foods edible. cyanide removal Cassava is a common staple food (mani hot esculenta).
“Foresight and understanding of mechanisms do not have Requirements for the initial appearance of external fermentation, write researchers. “Our early ancestors may have simply taken food to a common place, left it there, and eaten or added to it intermittently.”
Microorganisms present in the previous food can inoculate the new food and cause fermentation. As our brains grew larger, humans may have been able to better understand fermentation.
The research team emphasizes the need for empirical research to support or refute hypotheses, including microbiological studies, comparative analyses, and genetic and genomic investigations.
“Transferring enteric fermentation to an external cultural practice may have been an important innovation for humanity,” the authors write. conclude“It demonstrated the metabolic conditions necessary for selection for brain expansion to take hold.”
This research communication biology.