The first question asked and answered by Vanderbilt University researchers in their press release: “Why do humans take so long to mature compared to other animals? Look at your neurons! ". Their work, presented at the 2018 Neuroscience Congress and published in the Journal of Comparative Neurology, suggests that lifespan after reaching sexual maturity in humans and other warm-blooded species actually depends more on the brain than on the body. .
The Nashville researchers conclude here more specifically that animals with the largest bodies or the slowest metabolisms do not live the longest; they are the ones with the most neurons in the cerebral cortex, regardless of body size. Their more anthropological than psychological study thus estimates at 75% the “weight” of the number of neurons present in the cortex in the variation in the longevity of a species. The main author, Suzana Herculano-Houzel, associate professor of psychology and biology thus minimizes, with these new data, the impact of body size and metabolism, two often inconsistent influences, on the longevity of a species.
The study examines more than 700 warm-blooded animal species from the AnAge database, an exhaustive database on longevity, then compares these recordings with the number of neurons in the brain of the different species. In practice, by what methodology? The author calls his method of analysis “brain soup”. This involves taking brain tissue, extracting the cells, then applying fluorescent tags to the nuclei floating in the "solution", counting them. The team thus produced the first accurate count of the number of neurons in the human brain, around 86 billion, making it "just an enlarged primate brain." And analysis of these counts shows that longevity is dose-dependently associated with the number of neurons in the cerebral cortex.
- The more cortical neurons a species has, the longer it lives and it doesn't matter whether it's a bird, a primate or any other mammal, its size and how quickly it burns energy.
What about humans?While humans are sometimes seen as an evolutionary exception characterized by a prolonged childhood and post-menopausal period, this research is wrong: humans take exactly the time needed to "mature" as predicted by this new model based on the number of cortical neurons. And it's the same for their lifespan from sexual maturity. Thus, the human species is characterized by an extremely long childhood and adolescence to allow learning and social interactions. The new data show that humans are no exception to other mammalian species in this pattern of longevity: given the number of neurons in our cortex, humans take the time necessary to reach sexual maturity and live well the duration associated with the number of their cortical neurons. All of this is described as “logical”: “the more neurons you have in the cortex, the longer it takes you to reach maturity on a physiological level, but also on a mental level. A delay that leaves humans with more cortical neurons the time to learn, in particular through more complex interactions with their environment”.
So more cortical neurons, longer lives but also more opportunities to pass on to offspring… A theory certainly already mentioned but which is based here on a precise count of the neurons of the cortex.
What is the link between the neurons of the cortex and longevity?“The data suggests that warm-blooded species accumulate damage at the same rate as they age. But what harms life is damage to the cerebral cortex more than to the rest of the body. Because unlike the rest of the body, which renews its cells, cortical neurons are supposed to last a lifetime. For these scientists, beyond its overall cognitive function, the cortex is therefore also a key to longevity. “The cortex is the part of our brain capable of making our behavior complex and flexible, it also gives our body adaptability, as it learns to react to stress and precede it. While it is essential to maintain healthy physiological functions, it is equally essential to feel, analyze and predict,
In practice, what implications? Aging begins when humans and other species reach adolescence, and it then becomes impossible to recover (or almost) neurons.
Taking care of your mind and the health of these cortical neurons, by adhering to a healthy lifestyle for example, is therefore “the best way to live a long and healthy life”.
.jpg)
