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Brain Soup

By Shlomo Maital

Suzana Herculano-Houzel

How do you count the number of neurons (brain cells) in a brain (whether human or animal)?   Dr. Suzana Herculano-Houzel, Vanderbilt University, has found a creative way.

   Previously, the method was to take samples of brain tissue, freeze it, put it under a microscope and count neurons. But this was inaccurate, because neuron density in brains varies widely, depending on the place within the brain.   Using this method we thought the brain had 100 billion neurons. That’s not a lot – elephants have three times more!

   Herculano-Houzel read an old 1970’s study, suggesting, why not measure the amount of DNA in a brain, then divide by the amount of DNA per neuron?   Hmmm… problem is, DNA per neuron varies widely.

   So she developed a new, creative method.   Take a brain.   Puree it using a blender. (Honest!).   Brain soup, she calls it.   Mark the neurons with a chemical dye, then mark again with a red dye to mark the nucleus of the neurons. Neurons have only one nucleus, like all cells. So if you count the neuron nucleuses, you can compute how many neurons there are in the brain.

   Answer?   86 billion.   Or, 14% fewer than we thought (100 b.).

   So why are humans so smart? The key part of the brain, that makes us smart, is the cerebral cortex, that wrinkled outer part of the brain. Because it is wrinkled, it has a lot of surface area, enabling more neurons to pack it.   Turns out we have 16 b. neurons in the cerebral cortex, while orangutans and gorillas have 9 billion, and chimps have 6 billion. (Those are respectable numbers – those primates are clever!).

     And those 16 b. neurons in the cerebral cortex are waht makes us smart, and it is probably where Dr. Suzana got the idea…   Hey, why did no-one else think of it before?

How We Humans Can Learn from Chimpanzees

By Shlomo Maital


   BBC World Service’s Science Hour program is outstanding. On March 30, one of the topics was animal behavior. It was recalled how Jane Goodall saw chimps use twigs to get ants from inside anthills, and proved that animals know how to use tools. Then broadcaster Adam Hart asked, do animals think like humans? Do they have moral principles?

     The fascinating research by Emory University researcher Frans De Wall, a Dutch primatologist, was mentioned.  He studies whether animals empathize, i.e. understand and sympathize with other animals? They do indeed. Chimpanzees go over to chimps who lost a fight, and put an arm around them to comfort them. Yawn contagion is a predictor of empathy (if someone else yawns, causing you too to yawn, you are empathic). Chimps who saw videos of yawning chimps were likely to yawn themselves if they knew the chimp involved, i.e. had a reason for empathy.  

     But do animals have a sense of equality and fairness? De Wall reports:  “We did experiments with capuchin monkeys.  They are very sensitive to who gets what.  In our experiments we had 2 monkeys side by side. We gave them pebbles and they had to give them back to us, to get a reward. If both got the same reward, they perform this task 25 times in a row without fail. But If one gets a grape, another gets some cucumber, and grapes are far better rewards, the chimp who gets cucumber gets upset, protests, throws away the food (similar to human reactions), and goes into protest mode, or strike.  No more returning pebbles!”

     With The Economist’s cover story on Crony Capitalism, new attention is being focused on the obscene salaries capitalist managers pay themselves, especially those in banks, insurance companies, hedge funds and financial services.   The animal studies reveal a key point. It is part of our evolutionary DNA that societies should be fair. Fair societies are cohesive, and thus survive better and longer than selfish unequal ones. This began with primates, chimps and apes, and has transferred to human society too.   Crony unfair unequal capitalism, where a handful rip off the majority of working people, will simply not survive. One way or another, the people will find a way to put a stop to it, just like De Wall’s chimps.

   Check out De Wall’s books: Our Inner Ape, and Chimp Politics. In many ways, chimp society is more advanced than our own human society in the age of rip-off capitalism.

Blog entries written by Prof. Shlomo Maital

Shlomo Maital