Human communication

Neuroscience Explains Exactly Why We Should Be Thankful For Our Brain


Here’s something new you can be thankful for on Thanksgiving: the long evolutionary journey that gave you your big brain and your long life.

I know I am grateful. But then, I’m the one proposing that we humans revise the way we tell the story of the birth of our species.

Brains made of cells, but how many?

Back when I had just received my freshly prepared doctorate. in neuroscience and I started working in science communication, I found that 6 out of 10 people with a university education thought they were only using 10% of their brain. I’m happy to say they’re wrong: we’re using it all, in different ways at different times.

The myth seemed to be supported by statements in textbooks and serious scientific articles that “the human brain is made up of 100 billion neurons and 10 times more supporting glial cells.” I wondered if these numbers were facts or guesses. Did anyone actually know that was the number of cells in the human brain?

No, they didn’t.

Neuroscientists have had a rough idea. Some estimates suggest 10 to 20 billion neurons in the human cerebral cortex, others some 60 to 80 billion in another region called the cerebellum. With the rest of the brain known to be fairly sparse in comparison, the number of neurons in the entire human brain was certainly closer to 100 billion than just 10 billion (far too few) or 1,000 billion (far too many).

But there we were, neuroscientists armed with sophisticated tools to modify genes and shed light on parts of the brain, still unaware of the makeup of different brains and the comparison between the human brain and others.

Counting Neurons in Brain Soup

So I devised a way to easily and quickly count how many cells a brain has. I spent 15 years collecting brains and then turning them into soup that I examined under a microscope. This is how I got the hard numbers.

As it turns out, there are many ways to bring brains together: primates like us have more neurons in the cerebral cortex than most other mammals, regardless of the size of their brains. A brain can be big but made up of relatively few neurons if the neurons are huge, like in an elephant; primate neurons are small, and bird neurons are even smaller, so even the smallest bird brain can hide a lot of neurons. But never as much as the biggest primate brain: ours.

When comparing brains, we care about the number of neurons in the cortex because it is the area of ​​the brain that allows us to go beyond just sensing and responding to stimuli, allowing us to learn from the past and make plans for the future.

If people had continued to eat exclusively raw foods, like all other primates do, they would have to spend over nine hours a day searching, collecting, picking and eating to feed their 16 billion cortical neurons. Forget about discovering electricity or building planes. There would be no time to look at the stars and wonder what could be. Our great ape cousins, always raw foodies, still have at most half as many cortical neurons as we do – and they eat more than eight hours a day.

But our ancestors figured out how to trick nature into getting more with less, first with stone tools and later with fire. They invented cooking and changed the history of mankind. Eating is faster and much more efficient, not to say delicious, when the food is pre-treated and processed over a fire.

With a lot of calories available in much less time, the new generations have acquired bigger and bigger brains. And the more cortical neurons they had, the longer children remained children, the longer their parents lived, and the more the former could learn from the latter, then from the grandparents, and even from the great-grandparents. Soon cultures flourished. Technology has flourished and survived through school and science, becoming more and more complex.

With so much culture to share, what makes us modern humans has become so much more than our human biology. Being born with a lot of neurons gives us the potential for a long, slow life, a life where each of our brains has the chance to be educated by what generations before us have taught us, and to educate the next. We will remain modern humans as long as we are ready to gather around tables to celebrate our differences and share our hard-earned knowledge, stories of success and failure, hopes and dreams.