The Human Brian is Just Bigger Not Special or Exceptional

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The myth of human biological and brain specialness, called exceptionalism, is used as the basis for most of modern and pop psychology and neuro-stuff.   It is not only wrong but badly wrong and dishonestly misleading.  it is also an obstacle to good new ideas and waste of lots of time and research money.  But since this set of false beliefs fits our magical cultural beliefs in humans being special it sells really well.  Bad ideas that lie about things wish to be true always are popular.

A new study however, is a first stake in the hear of this zombie and undead idea below is a digest of some of the paper.Number of neurons makes human brain powerful, not structure…Human brains, being bigger, simply have far more neurons

Scientists say it was the development of cooking and the accompanying calorie boost that allowed humans to develop a much bigger brain.

…the number of neurons and white matter connectivity of the human prefrontal region did not expand disproportionately to other cortical areas in human evolution.

New research suggests the human brain isn’t structurally different than those of primates, it’s just bigger and has more neurons.

New research suggests the human brain isn’t special. It’s just a bigger, better primate brain. “People need to drop the idea that the human brain is exceptional,”

Just like the brains of macaques, baboons, marmosets, galagos, owl monkeys and capuchins, the human brain devotes 8 percent of its neurons to the prefrontal cortex. The ratios of gray and white matter are also similar.

“Our brain is basically a primate brain…Because it is the largest primate brain, it does have one distinctive feature: It has the highest number of cortical neurons of any primate. Humans have 16 billion compared with 9 billion in gorillas and orangutans and six-to-seven billion in chimpanzees. It is remarkable, but it is not exceptional. “Those early tool makers had brains about the same size as gorillas…But, beginning about 1.8 million years ago, the brains of our ancestors began growing steadily, tripling in size over the next 1.5 million years.”

Prepared foods were made possible by the first stone tools. By slicing, dicing and mashing, early humans got more calories without using as much energy.

Human brain evolution is often considered synonymous with cortical expansion, in particular of the prefrontal cortex, a cortical region required for our remarkable cognitive abilities such as personality expression, planning, and decision making. In this study, we show that the expansion of numbers of cortical neurons in human and nonhuman primate evolution occurred in a similar manner across the cortex, without an increase in the relative number of neurons in the prefrontal region, and without a relative increase in the number of cells in the prefrontal white matter. One thing that distinguishes the human brain from other primate brains is thus not the relative size of its prefrontal cortex but its absolute number of neurons.

Human evolution is widely thought to have involved a particular expansion of prefrontal cortex…Here we show that:

– the prefrontal region of both human and nonhuman primates holds about 8% of cortical neurons, with no clear difference across humans and other primates in the distribution of cortical neurons or white matter cells along the anteroposterior axis.
– Further, we find that the volumes of human prefrontal gray and white matter match the expected volumes for the number of neurons in the gray matter and for the number of other cells in the white matter compared with other primate species.
– prefrontal cortical expansion in human evolution happened along the same allometric trajectory as for other primate species, without modification of the distribution of neurons across its surface or of the volume of the underlying white matter.

The most distinctive feature of the human prefrontal cortex is its absolute number of neurons, not its relative volume.

Human evolution was long thought to have involved a selective enlargement of the prefrontal cortex… However, recent publications showed that the gray matter of the human prefrontal cortex has the expected volume for a primate with the same brain size and therefore does not diverge from the allometric rule of great apes…human subcortical white matter in each cortical region also has the volume expected for the number of cortical neurons in the region as predicted from the relationships that apply to nonhuman primate species

…human evolution has involved neither a significant expansion of prefrontal white matter volume beyond the expected for the local number of neurons nor a significant expansion of the white matter volume beneath other cortical regions.

Here we show that the human prefrontal region, in comparison with that of other primates, has:

(i) the expected number of neurons for its gray matter volume,
(ii) the expected number of neurons for the total number of neurons in the remainder of the cortex,
(iii) the white matter volume expected for the number of neurons in the region, and
(iv) the expected volume and number of other cells in the white matter for the volume and number of other cells in the remainder of the nonprefrontal subcortical white matter.

In particular, we find that the prefrontal region of the cortex (anterior to the corpus callosum) holds a similar 8% of all neurons in human and nonhuman primates alike. All these results point to the same two conclusions:
– that primate evolution did not involve a shift in the distribution of cortical neurons toward prefrontal regions and that human evolution,
– in particular, did not involve an expansion of the relative number of neurons or relative total length of myelinated fibers in the prefrontal region over other primates.

…human frontal cortex is not proportionately larger than expected for a nonhuman primate of our cortical size, with no evidence of a relative enlargement of the human prefrontal white matter…the distribution of neurons and white matter is indeed similar in human and nonhuman primate species. We find this similarity all the more remarkable given that our sample does not include nonhuman ape species.

What Distinguishes Humans from Other Primates? …The increased number of nonprefrontal neurons presumably contributes to improving nonassociative functions in human brains relative to other species. Additionally, an overall increase in the number of cortical areas proposed for primates with increasing cortical size, and therefore increasing number of neurons, should also contribute to adding complexity to sensory-motor processing in larger cortices.

Not surprisingly, the same 8% of all cerebral cortical neurons found in the prefrontal region correspond to a much larger absolute number of neurons in human (1.3 billion) than in other primate brains (e.g., macaque, 137 million), regardless of the relative size of the prefrontal cortex. Although a number of genetic changes specific to the human brain have been found and certainly play some role in human cognition, we propose that this larger absolute number of neurons in human prefrontal, associative cortical regions is the main factor underlying the complexity of our cognitive abilities in comparison with other primates, and possibly all other mammals. As for nonassociative regions, the ensuing increase in number of cortical prefrontal areas expected with an increased absolute number of neurons and absolute cortical size would be an additional factor to contribute to increased complexity of associative processing in humans compared with other primate species.

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