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New Vanderbilt study reveals how long humans and others – and when they reach sexual maturity – may have more to do with their brains than their bodies More specifically, it is not animals whose bodies are more large or slower metabolism who live longer; they are animals with more neurons in the cerebral cortex, regardless of the size of the body.
"Whether it is birds, primates or humans, the number of neurons present in the cortex of a species predicts about 75% of the variation in longevity from one species to another, "said Associate Professor of Psychology and Biology of the author of the science study Suzana Herculano-Houzel.
Body size and metabolism, compared to usual standards for comparing animals, predicted only between 20 and 30% of longevity by species and left many inconsistencies, such as birds that live ten times longer than mammals of the same size.
More importantly, humans were considered a "special" evolutionary quirk, characterized by a long childhood and post-menopausal periods. But this research, published in the Journal of Comparative Neurology, finds that this is not correct. Humans are as slow in maturing their number of cortical neurons as they are – and live as long as expected afterwards.
L & # 39; STUDY
In this study, Herculano-Houzel examined more than 700 warm-blooded animal species from the AnAge database, which collects comprehensive data on longevity. She then compared these recordings with her detailed data on the number of neurons in the brain of different species of animals.
Herculano-Houzel coded the data colors for hundreds of species and found that parrots and songbirds, including corvids, consistently live longer than similar body mass primates, which in turn live longer than non-primate mammals of similar body mass.
"Similarly, for similar specific basal metabolic rates, parrots and songbirds live longer and take longer to reach sexual maturity than many mammal species, particularly non-primates," said Herculano. -Houzel.
She had previously observed this phenomenon: her previous studies on brain composition showed that parrots and songbirds had more cortical neurons than primates of similar size, which had more cortical neurons than any other mammal of comparable body size. .
His new analysis confirmed his suspicions: this longevity increases uniformly in warm-blooded species as well as the absolute number of neurons in the cerebral cortex.
"The more a species possesses cortical neurons, the longer it lives for a long time – no matter it's a bird, a primate or any other mammal, its size and size." its speed to burn energy, "explains Herculano-Houzel.
ARE HUMANS UNIQUE? ASK GRANDMA
Anthropologists and researchers interested in evolution and human behavior have relied on the assumption that one of the peculiarities of the human species is that humans have a Extremely long period of childhood and adolescence to enable learning and social interactions. If larger animals live longer, gorillas should live longer than humans – but this is not the case: humans survive. A preferred hypothesis is that being cared for by grandmothers could have caused humans to delay sexual maturity and increase postmenopausal longevity beyond expectations.
But new data from Herculano-Houzel show that humans are not an exception from other mammalian species. Given the number of neurons in our cortex, humans take the time to reach sexual maturity – and live as long as expected for their number of neurons. It turns out that body size does not matter in terms of longevity.
"Now, we can say that humans spend as long in their childhood and live exactly as long after they reach maturity as we would expect for the number of neurons in our cerebral cortex", declared Herculano-Houzel.
Which is longer, compared to other species – gorillas included – simply because humans have the most neurons in the cerebral cortex.
"It makes sense that the more neurons you have in the cortex, the longer it takes for a species to reach that point where it is not only physiologically mature, but mentally capable of being independent," he said. Herculano-Houzel. "The delay also gives species with more cortical neurons more time to learn from experience because they interact with the environment."
And if longer lives also accompany more cortical neurons, these species will also benefit from greater overlap between generations and will thus offer more opportunities to pass on what they have learned.
"Which means that the grandmother is still fundamental in the lives of those who have a lot of cortical neurons, and that's probably not the reason why our species has a long life," says Herculano-Houzel.
CORTEX FUNCTION
What is the link between having more neurons in the cortex and living longer? Herculano-Houzel says that's the new big issue to which researchers must attack.
"The data suggest that warm-blooded species accumulate damage at the same rate as their age, but what's life-threatening is damage to the cerebral cortex, not to the rest of the body." The more cortical neurons you have, the more you'll have enough time to keep your body functional, "she says.
Unlike the rest of the body, which receives new cells that replenish old ones, cortical neurons should last a lifetime.
Although the cortex is generally associated with cognition, Herculano-Houzel believes that a much more fundamental function of the cortex is the key to longevity.
"The cortex is the part of your brain that is able to make our behavior complex and flexible, yes, but it goes well beyond cognition and mental and logical reasoning," said Herculano-Houzel. "The cerebral cortex also gives your body an ability to adapt, as it adapts and learns to react to stress, what you do, what you feel and what you plan to achieve, and it's apparently a determining factor for longevity, "she adds.
BRAIN SOUP
Herculano-Houzel pioneered the method of rapid and accurate measurement of the number of neurons in the brain. She creates a "brain soup" by taking brain tissue and breaking down the cells, then applying fluorescent labels to the nuclei floating in the "brain soup" and counting them.
In collaboration with Jon Kaas, Distinguished Professor of Psychology at Vanderbilt, she studied the number of neurons composing different brains of primates, including great apes. With her colleagues in Brazil, she produced the first accurate count of the number of neurons in the human brain – an average of $ 86 billion, which simply makes her an enlarged primate brain.
CARE FOR YOUR BRAIN!
Aging begins when humans and other species reach adolescence, and it is impossible to recover neurons. In fact, research shows that humans can lose neurons in the prefrontal cortex. So, Herculano-Houzel says that taking care of your mind and keeping these cortical neurons healthy and busy is the best way to live long and well.
Source:
https://www.vanderbilt.edu/
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