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With a discreet profile and an easily understandable discourse, her Brazilian accent is still as strong as when she lived in her country.

With a degree in Biology, her interest in Neuroscience would only grow much later. She completed her post-graduation in the USA and lived in Germany for four years, where she completed her Ph.D. Upon returning to Brazil, she worked in scientific communication and it was the work she developed at the University of Rio de Janeiro that led her to focus on researching brains, and what they are made of.

After 15 years trying to understand how the human brain compares to other brains of the animal species, she realised that several of her peers looked upon the human brain as something special and unique, not even comparable to those of other species.

Her grandfather was a general practitioner and her grandmother was from Vila do Conde, so she has a global heritage. She moved the US about two years ago. She received an invitation from Vanderbilt University, in Nashville, a University that she was already visiting ten years ago and where she shared ideas with researcher John Kaas, who also studies primate brains.

She says, with extreme happiness, that leaving Rio and going to the US was the best thing that could have happened to her. "I had very bad work conditions, I was lucky that my research method was so cheap. With little resources, I collected the brains of different animals species, through a fund that I received from the state, I went to other countries and they gave me samples and I returned to my micro-laboratory in Rio". She criticises a country whose budget for science is minimal, she says that Brazilians suffer "from an inferiority complex"; while outside the country, interest in science was growing and growing, inside it was tapering, "only what is happening outside is good, people are only able to value something when they look from the outside, it is a copycat culture in which something is only valued inside when it is done by others".

She is currently living in a small and familiar city, where she is not afraid to get home late, she doesn't even have to think about where she parks her car, and what's more, she has the intellectual support of her colleagues who are happy with her progress.



Guest Speaker at the CAML PhD Meeting, Suzana Herculano-Houzel has recently published a book - A Vantagem Humana, Como o nosso cérebro se tornou super poderoso. She came to talk about brain sizes and the human brain's advantage over those of other animals. "We don't have the largest animal brain, elephants have a brain three times larger than ours and a whale's brain in six times larger than a human brain. So, despite not having the largest brain, it was understood that this was due to an extraordinary feature of the human brain. But I realised that maybe it was only because we hadn't understood the most basic thing about the brain and my question was, what is the brain actually made of? When you have two brains with the same size, will they have the same number of neurons? If you look at a brain larger than the human brain, does it have proportionally more neurons because it is larger?".

Based on the assumption that brains are all made of the same material, Suzana questioned whether the size of a brain would be proportional to its number of neurons. But knowing from the outset that the human brain was not the largest one, what made it stand out?

If the brain with more neurons has "more lego blocks", as she puts it, then does the brain with more lego blocks think better? But how do you compare different species and measure their neurons?

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The technique may seem strange, but what Suzana decided to do to measure the brains was to turn them into soup. Can you talk to us about the technique and your thought process?

Suzana Herculano: By undoing the tissue and dissolving the cells we are able to count the cell nuclei; by counting the nuclei, we count the cells. By counting the brain, region by region, in ten minutes you can, in a real number, count how many cells there are. This soup is counted under a microscope, then using dyes for each region of the brain, all the areas are counted. The technique was first used in rat brains, but over time we have progressively broadened the spectrum of the samples. And then we found the first two clues: the first was that every group of animals had different types of brain, and the second was that primates are different from all the other groups. And this is because their neurons don't grow, their brain grows more neurons. In all other groups of mammals the more neurons in the cerebral cortex, the bigger they are, but not in primates. Primates grow more neurons without them increasing in size and we still don't understand why. That means that when the primate brain is compared to that of another mammal with the same brain size, the primate brain has more hidden neurons, but less volume than that of the other mammal. The primate way of adding more neurons to the brain, whatever that may be, is very economical, it's with neurons that keep the brain small. The size of the brain is deceptive and, eventually, the consequence is that when we compare our brain to that of primates, to a brain with a similar size but from a different type of animal, our brain hides a huge number of neurons.

We are the species with the greatest number of neurons in the main cortex, our brain has no extraordinary evidence.



So what do we have that's extraordinary?

Suzana Herculano: The question then changed and was, what allowed our species to accumulate so many neurons so fast in evolutionary terms? Why is it that the gorilla, or the elephant, are bigger than us and don't have more neurons? The answer concerns an energy limitation. We are animals and we don't photosynthesise and that means that we have to eat, because all the energy in our bodies has to be ingested.

Access to supermarkets and the fact that we have refrigerators allows us to have enough food, as long as there is no lack of access. But, out in the real world, animals need to look for food, hunt it and that takes time and is limited by the size of what their mouth can bite. In the case of primates, we did the maths on how much energy this animal needed, and we realised that an orangutan is at the end of the line, as eight hours can elapse between looking for food or eating. Eight hours is the limit they can reach before they start losing weight.

Then we realised that there was something complex and that distinguishes us from all other species, which is that we cook, we transform our food before putting it in our mouths because we use pre-digestion. So, our body also spends less energy on eating. But more than that, we only swallow soft and liquid food in our mouth; when the food reaches the stomach and intestine, 100% of the paste is already available to be fully used, energetically speaking. Realising the impact of cooking food has completely changed my way of looking at the kitchen and even at our usual living habits. But can you see what it took us to get here? And how we can lose all of this?

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So the great revolution happened because we cook food?

Suzana Herculano: This is the difference in human biology and what it gives us and what we do with it. Human beings have at least double the neurons in the cerebral cortex and if, as a species, we begin with all these additional neurons, of course this gives us a huge advantage. But it's not only that, because that is just raw material and you still haven't learned how to do anything with it. What good is it if I give you a bucket of lego blocks if you don't know how to build a great building with them? What happens in the individual is that they have a process of brain development training and that depends on the information that is absorbed and not on what is in the genes. This interaction involves studying, meeting people. That takes time, but culminates with learning, and the application of that learning. There is therefore a huge difference between what our biological capacity is and what we learn to do with the information we absorb.

Thus, as we disregard the kitchen, we also disregard school and the education we receive; it's the know what and the know-how; we are now so able to do things that we don't even value them anymore.

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Because we take everything for granted.

Suzana Herculano: We take everything for granted, so we disregard things. It is necessary to expose people to the attribution of knowledge. If there are not enough people to pass on, at least, what has been discovered before our time and, if possible, to go a little further, we will lose everything we have conquered and we will become merely biologically human again. We will be left with a huge bucket of lego blocks we don't know how to use.

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Do we run the risk of regressing as a species?

Suzana Herculano: It is certainly a major risk for every generation. I love reading science fiction books and fiction has taken on a new dimension for me now that I research. Several of these books have elaborated on the mental experience of wondering how long we would last if there were no more schools and if there were no more people with some type of knowledge on earth. And we're only a generation away.

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Really?
Suzana Herculano: Yes. Let's see some concrete examples. When the sun goes down and I turn on the light, it is because I press a button, but this button is connected to transformers that were built by someone, someone who thought of how to keep everything connected; so, a few hours after losing the people who know how to take care of this matter, we know that we will lose electricity. And what do you lose by losing electricity? This is the danger; we are so good at reaching this standard of living that we no longer worry about how to maintain it and we forget that, what we are, depends on keeping everything alive and this goes far beyond our biology. I've earned a PhD, but I don't know how to build a pencil, I don't know how to hunt, and I'm not sure how to make a fire. All these things I get are ready for me to use. We must be aware that no one can, or should, master all the knowledge, we need to work as a knowledge network.

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And yet, more and more people think we know everything. Is that your message?

Suzana Herculano: Exactly, but the question is that, as a species, it is true that we know more and more, the problem is that this is happening at the same time as each of us is increasingly small in the global scheme of things. Mankind, a long time ago, transcended the human being, but each and every one of us is a very small piece and knows something that adds to this whole. It is obvious that no doctor knows everything, but nowadays a doctor knows a lot more than he would have 100 years ago. Today, proportionally, a doctor studies for longer and gains more techniques and therefore, in absolute terms, it is clear that he knows a lot more, but the sense of proportion is relative and should always be taken into account. The question is: How much does each of us know? Or how much does each of us know, compared to everything around us and in the world? If it is just how much each of us knows, then it is an enormity, but we only get to know more and more of a single area, proportionally, smaller and smaller. One more reason that shows how we depend on everything around us. The transmission of knowledge from one generation to another is absolutely necessary. See how governments also give so much importance to sharing knowledge and keeping everything alive.

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If we gave primates constant and assimilated food, as we eat it and without forcing them to hunt and spend so much time and energy, would that make them grow more neurons?

Suzana Herculano: They would definitely get fatter. Just like us. But having more neurons is not the answer to the question of where energy comes from, we still haven't found an answer for that. It's not enough to give primates more food, the explanation is in evolution and that is a spontaneous advantage that we don't dominate. Energy only thrives if it is generated by a viable variation. The human species does not have a larger brain than it should, compared to the gorilla, the gorilla does not have enough energy to have a brain with more neurons.

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Créditos de imagem: Jorge Bispo

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Joana Sousa

Editorial Team