evolutionary

The human being is the primate that sleeps the least. Science is clear that it is a “radical evolutionary experiment”

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We spend a third of our lives sleeping, yet the most common complaint in modern society It’s the lack of rest. We tend to blame screens, work stress and artificial light for robbing us of hours of sleep, but here evolutionary anthropology has a much more forceful answer: human beings are genetically designed to sleep less than any other evolutionary relative. It is studied. It is not something that we see from afar as a mere hypothesis, but researcher David R. Samson, professor of Evolutionary Anthropology, recently published a book that includes the results of his research. And the truth is that, after living with hunter-gatherer tribes like the Hadza in Tanzania and the BaYaka in the Congo, their conclusion is resounding: humans are an absolute biological anomaly. We are the great early riser. If we take out the calculator and the meter, a primate more or less of our same average body mass, brain size and diet should sleep about 9.5 hours a day. But this figure is limited to a fairly select few people, since we actually sleep around 2.5 hours less than our evolutionary biology predicts, making us the primates that sleep the least of all. This is a pretty clear conclusion. if we compare ourselves with other species that have very high sleep rates, as can be seen in the following list: Chimpanzee: between 9.5-11.5 hours a day. Gorilla: 10-12 hours. Pig-tailed macaque: 14 hours. Night monkey: 17 hours. Because? How is it possible that with the most complex and energetically demanding brain in the animal kingdom we sleep so little? The answer seems to lie in the “deep sleep” hypothesiswhich suggests that evolution forced us to have a much deeper and more efficient sleep to sleep much less than the rest of the hominids. For example, humans spend approximately 25% of our rest time in the REM phase, which contrasts with species such as African green monkeys, which They only dedicate 5% to this phase. But in addition, human sleep has a lower proportion of light sleep, since in return, it has a higher proportion of deep sleep. A necessity. Having a much shorter rest was not a whim of ours, but rather a matter of survival, since by leaving the safety of the trees, where our ancestors slept safely, and descending to dry land, the risk of predation skyrocketed. Regarding shorter sleep, evolution promoted several mechanisms to guarantee our survival, such as sleeping next to the fire and in large groups for greater security. But in 2017 a study showed that natural variation in chronotype allowed someone to always be awake standing guard during the night. Don’t blame the screens. It is tempting to think that we sleep for about 7 hours because electric lights and smartphones have altered us in this modern life. But this is not the case, because after analyzing the sleep of the Hadza, who are a hunting community in Tanzania without access to electricity or mobile phones, it was shown that their patterns are identical to ours, sleeping 6.25 hours a night and maintaining a sleep efficiency of 68.9%. Images | MediaEcke In Xataka | We’ve been sold melatonin as the ultimate harmless sleep supplement. Science does not think the same

The shape of the hands is one of the last evolutionary mysteries of the human being. And we are one step closer to solving it

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Our hands are, without a doubt, one of the wonders of biological engineering, since for a long time, the dominant evolutionary narrative has focused on how our anatomy transformed to allow precision grip and the manufacture of complex tools. However, if we look beyond the fingers and focus on the wrist, the bones tell a much older and more surprising story. New tests. A comprehensive published study in the magazine Proceedings of the Royal Society B has put on the table quite important evidence about how our ancestors moved. And the conclusion is that the morphology of our wrist retains an undeniable echo of a common ancestor adapted to walking supported on the knuckles. How they have done it. To reach this conclusion, the researchers have not relied on isolated conjectures, but on a large-scale anatomical analysis. The team analyzed more than 2,037 carpal boneswhich are what form the wrist, belonging to different species of primates, crossing these data with the anatomical analysis of 55 fossils of extinct hominins. What they discovered by mapping all this morphology is that human wrist bones don’t look like those of most primates, but instead share deep structural similarities specifically with African great apes. It’s not a coincidence, since it responds to the biomechanical adaptations necessary to support the weight of the body on the hands when they are closed. That is, although today we use our wrists for complex tasks such as typing, painting or even performing surgery, their architecture was designed for walking on the knuckles. Cautiously. Does this mean that our ancestor walked on his knuckles with absolute certainty? In science, closed statements are dangerous, and the authors of the study themselves are cautious, since they do not present this ancient practice as an irrefutable dogma, but as the most consistent and plausible interpretation according to the anatomical evidence on the table. Its evolution. Our body did not evolve suddenly to its current form, but rather went through different phases at different rates. Here the study shows this phenomenon in our hands, since, while the general structure of the wrist has preserved those primitive evolutionary signals shared with African apes, other parts of the hand changed later. Specifically, adaptations associated with fine, precision manipulation appeared much later in our evolutionary lineage. In Xataka | We had always believed that evolution had been arrested for thousands of years. The redheads were telling us the opposite

“Going to the gym for an hour” is not worth spending eight hours sitting. And there is a deep evolutionary reason for that.

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They have slipped it on us and it is time to recognize it. For years, the gym boom has been received with enthusiasm: having ubiquitous and accessible sports facilities to get us out of our sedentary routine can only be understood as something positive. And yet, the way sport has entered our lives is deeply problematic: we have managed to create a “compartmentalized model” of physical activity that is leaking everywhere. So “going to the gym” doesn’t work? No, it’s not that. It’s not what the evidence says. Intense exercise is helpful. Very useful. And it is always better than doing nothing: but the idea of ​​going to the gym for an hour and that’s it forgets that the relevant unit is not the hour at the gym, but the energy pattern of the 24 hours a day. Let’s put it another way: Why do the Hadza They do not burn more calories than office workers despite walking 12 km a daywhy weight loss gym programs consistently disappoint or why the WHO has begun to separate “exercise” from “sit less”? The answer to these three questions is the same: the evolutionary biology of the human being. Two lines of research that converge at the same point. Between 2012 and 2018, a team from Duke University coordinated by Pontzer discovered that the body It is not dedicated to linearly adding exercise expenditure to basal expenditure. What it does is compensate for it (reducing expenditure on other vital functions such as inflammatory, reproductive processes or metabolic control). That is, doing an hour (or more) of intense exercise does not have to increase total energy expenditure. The second line of research arises from comparing people with the same weight and height. In ’99, the Mayo Clinic discovered that the daily difference in energy expenditure can be attributed to things like walking, standing, housework, and other types of small unconscious movements. To this we must add that a sedentary lifestyle is, in itself, a risk factor. In 2016, Ekelund and his team discovered that between 60 and 75 minutes a day of moderate physical activity are needed to eliminate the excess mortality risk associated with sitting for 8 hours or more a day. That is, one hour of exercise does not solve the problem. And the problem is that the public conversation doesn’t realize it. It is unbalanced: the dominant imagination since the 80s sees doing “a handful of hours of exercise” as a way to “buy” health. The very long debate about how many steps to take each day is exactly the same. The issue, as I say, is that the evidence is clear that we are not buying anything. And then? Should we close the gyms? Nothing of the sort. The important thing at this point in 2026 is to begin to understand that the correct unit to think about our physical activity is the full day. As the WHO says“more activity is better than little; any activity is better than none; (however) reducing a sedentary lifestyle provides independent benefits” and is worth addressing regardless of the exercise we do. The idea of ​​”training for an hour and then spending the rest of the day calmly” does not hold water. Going to the gym is positive, but it is not a papal bull: intense exercise works as something that adds to leaving a sedentary lifestyle. It does not replace it. Image | Anupam Mahapatra In Xataka | Cereals yes, but wrapped in black cardboard: the packaging business aimed exclusively at men

We have been believing for more than a century that the appendix is ​​a useless organ and an evolutionary error. We were very wrong

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If there is an organ with a bad reputation in human anatomy, it is the appendix. For the vast majority of people, this small worm-shaped pouch connected to the large intestine only serves one thing: to become inflamed, to cause appendicitis urgently and have us undergo surgery. But the truth is that it is more useful than we thought, since science has seen that it has a great impact on our immune system and also in life expectancy. An evolutionary success. Something that marvels me about evolution is that it does eliminate everything that has no use for humans, but if the phylogenetic branch has been maintaining it, it is for a reason. and here a 2013 study analyzed the anatomy of 361 species of mammals and the results were devastating: the appendix is ​​not exclusive to humans and great apes, but has evolved independently at least 32 times. And the question is: why? This theory was later reinforced with a 2017 analysis which identified between 29 and 41 evolutionary gains of the appendix, compared to the very few losses that stood at less than seven. And in biology, when a trait evolves repeatedly in completely different lineages, it means one thing: it provides a crucial adaptive advantage for survival. Its usefulness. If it doesn’t help digest leaves as Darwin believed, then… What does it do? The latest research, including a comprehensive 2023 review published in The Anatomical Record, confirm that the appendix acts as a microbial reservoir and a support for the immune system. This way we know that the appendix is ​​filled with lymphoid tissue and is strategically located outside the “main flow” of the intestine. And it works as a kind of bunker for our microbiome, and in this way, when we suffer a severe intestinal infection that “sweeps away” our bacterial flora, the appendix releases beneficial bacteria hidden inside to quickly recolonize the intestine. And tested. A 2023 study showed that primates with appendages have a relatively lower risk of severe diarrhea episodes early in life, reinforcing their vital role as a protective shield against deadly infections. Its relationship with longevity. The most fascinating discovery about the appendix came in 2021, where a team of researchers published in the journal Ecology and Evolution a study in which they crossed data from 258 mammal species. Controlling for variables such as body size and phylogeny, they looked for patterns between the presence of an appendage and the lifespan of the species. The conclusion they drew was none other than determining that the presence of the appendix is ​​directly correlated with greater maximum longevity. And the reason is in positive natural selection. In this way, by drastically reducing mortality caused by infectious diseases and diarrhea, species with an appendix have a clear survival advantage that allows them to extend their life expectancy. Image | Eugene Chystiakov In Xataka | We have been measuring death wrong: science now believes that our biological expiration date is more hereditary than we thought

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