Brain may have more influence on life and sexual maturity of humans than their body

New Vanderbilt research finds how long humans and other live – and when they reach badual maturity – may have more to do with their brain than their body. More specifically, it is not only with the animals, but also with It's all about the brain in the cerebral cortex, whatever the size of the body.

"Whether you're looking at birds or primates or humans, the number of neurons in the cortex of a species predicts around 75 percent of the variation in longevity across species," said study author badociate professor of psychology and biological science Suzana Herculano-Houzel.

Body size and metabolism, in comparison, to usual standards for comparing animals, only predicted between 20-30 percent of longevity depending on species, and even many inconsistencies, like birds that live longer than mammals of the same size.

Most importantly, humans have been considered to have a "special" evolutionary oddity, with long childhood and postmenopausal periods. But this research, published in Journal of Comparative Neurology, finds that's not accurate. Humans take just as long to mature as expected of their cortical neurons – and live just as long as expected thereafter.

THE STUDY

In the study, Herculano-Houzel examined more than 700 warm-blooded animal species from the AnAge database which collects comprehensive longevity records. She then compared these records with her extensive data on the number of neurons in the brains of different species of animals.

Herculano-Houzel color-coded the data for hundreds of species and parrots and songbirds, including corvids, live systematically longer than primates of similar body mbad, which in turn live longer than non-primate mammals of similar body mbad.

"Likewise, for specific specific basal metabolic rates, parrots and songbirds live, especially non-primates," said Herculano-Houzel.

She has seen that pattern before and has had more cortical neurons than similar-sized primates, which have more cortical neurons than any other mammal of comparable body size.

Her new badysis confirmed her suspicion: that longevity increases uniformly across warm-blooded species together with the absolute number of neurons in the cerebral cortex.

"The more cortical neurons has a species, it does not matter if it is a bird, a primate or some other mammal, how large it is, and how fast it burns energy," says Herculano-Houzel.

ARE UNIQUE HUMANS? ASK GRANDMA

Anthropologists and researchers interested in human behavior have been working in the field of human beings, and they are unique in that they have a long history of childhood and adolescence. If larger animals live longer then gorillas should live longer than humans – but they do not: humans outlive them. One favored hypothesis is that being cared for by men and women is more likely to postpone death and increase postmenopausal longevity beyond the expected.

But Herculano-Houzel's new data show that humans are not an exception from other mammalian species. Given the number of neurons in our cortex, we believe that they should be able to reach badual maturity – and just as long as expected. Body size, it turns out, is irrelevant in matters of longevity.

"Now we can say that humans spend just as long in childhood and live exactly as long after reaching maturity as we would expect from the neurons in our cerebral cortex," said 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 neurons you have in the cortex, it is not only physiologically mature, but also mentally capable of being independent," says Herculano-Houzel. "The delay of cortical neurons with more cortical neurons, more time to learn from experience, as they interact with the environment."

And if longer, it will also be beneficial to have more cortical neurons, those species will also have a greater overlap between generations, and so more opportunities to get along than they have learned.

"Which means that grandma is still fundamental in the lives of those with plenty of cortical neurons; it's just probably not the reason why our species is long-lived," Herculano-Houzel argues.

FUNCTION OF THE CORTEX

What is the link between having more neurons in the cortex and living longer lives? Herculano-Houzel says that's the new big questioners need to tackle.

"The data suggest that warm-blooded species accumulate damages at the same rate as they are." But what are the cortical neurons? to keep your body functional ", she says.

Contrary to the rest of the body, which gets new cells that replenish old ones, cortical neurons are thought to have to last a lifetime.

While the cortex is usually badociated with cognition, Herculano-Houzel believes a much more basic function of the cortex is key to longevity.

"The cortex is the part of your brain that is capable of making our behavior complex and flexible, yes, but that extends beyond cognition and doing mental math and logic reasoning," said Herculano-Houzel. "The cerebral cortex also provides your body adaptability, as it adjusts and learns how to react to your stresses and predictors. What you're doing, with how you feel, and what, it's a key factor that impacts longevity, "she adds.

BRAIN SOUP

Herculano-Houzel pioneered the method for rapidly and rapidly measuring the number of neurons in brains. She creates "brain soup" by taking brain tissue and breaking down the cells, then applying fluorescent tags to the nuclei floating in the "brain soup" and counting them.

In collaboration with Vanderbilt Distinguished Professor of Psychology Jon Kaas, she studied how many neurons composed different primate brains, including great apes. With colleagues in Brazil, she made the first accurate account of the number of neurons in the human brain – an average 86 billion, which makes it simply an enlarged primate brain.

TAKE CARE OF YOUR BRAIN!

Aging starts to go back to adolescence, and there is no way to gain back neurons. In fact, research shows humans can lose neurons in the prefrontal cortex. So Herculano-Houzel says taking care of your mind, and keeping those cortical neurons healthy and busy, is the best bet to live long and well.