The big sapiens brain gave them (us) a huge evolutionary advantage. We humans are proud of our big brains, which are responsible for our ability to plan ahead, collaborate and create..

Packed inside our skulls are an average of 86 billion neurons - three times as many as our primate cousins..

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But how do we manage to develop so many brain cells? Researchers are one step closer to answering this question.

A new study shows that changing just one amino acid in a metabolic gene helps our brains develop more neurons than other mammals and more than our extinct relatives, the Neanderthals..

What makes our brains human has been of interest to neuroscientist Wieland Huttner of the Institute for Molecular Cell Biology and Genetics for many years.. Max Planck (g. Dresden, Saxony, Germany). In 2016, his team found that a mutation in the ARHGAP11B gene, which modern humans have and had in Neanderthals and Denisovans but not in other primates, causes more progenitor cells to be produced that develop into neurons..

But it's not just about brain size.. Our brains are about the same size as those of Neanderthals.. However, it is we, sapiens, who have created and are creating complex technologies that allow us to dominate among other mammals.. What is the main advantage?

Wieland Huttner and his team set out to find genetic differences between Neanderthals and modern humans, especially in the cells that give rise to neocortical neurons..

This area behind the forehead is the largest and most recently developed part of our brain and is where most of our cognitive processes take place..

The team focused on the TKTL1 gene, which in modern humans has a single amino acid change from lysine to arginine.. This is not the case with Neanderthals or other mammals..

Analyzing previously published data, the researchers found that TKTL1 is mainly expressed in progenitor cells called basal radial glia, which give rise to most cortical neurons during development..

Researchers injected both human and archaic versions of the gene into mice, which normally don't express either form during development. The brains of mice with the human version produced more basal radial glia, which in turn developed into more cortical neurons, than mice with the archaic version..

The team also wondered if TKTL1 affects the deep folding of the human brain, the geometry that allows us to compress extra neurons inside our skull.. In mice, these folds are completely absent, but in ferrets, despite the archaic version of TKTL1, they are present..

When researchers injected the human version of the gene into ferrets, the animals produced more cortical neurons and enlarged brain folds..

“I didn’t expect to see an increase in [wrinkles],” says first author Anneline Pinson, postdoc at Max Planck. It was amazing to watch, she said..

The discovery “highlights that this gene plays an important role” in shaping our big brains, Huttner says..

However, Christoph Zollikofer, a paleoanthropologist at the University of Zurich, believes that Huttner's team's data cannot resolve the debate about Neanderthal intelligence.. Brain size and number of neurons do not always lead to higher intelligence.

According to Zollikofer, the key to the powerful intelligence of sapiens should be sought in the number of connections between brain neurons..

Pinson and Huttner acknowledge this, but Huttner argues that “having more neurons is probably not bad either.”. And why there are so many of them in the human brain is now known.

As previously reported, an international team of scientists reported that the mud of the caves may contain intact DNA of ancient people..