๐๐ก๐ ๐ง๐๐จ๐๐จ๐ซ๐ญ๐๐ฑ ๐ฌ๐ญ๐๐ง๐๐ฌ ๐จ๐ฎ๐ญ ๐๐ฌ ๐ ๐ฌ๐ญ๐ฎ๐ง๐ง๐ข๐ง๐ ๐๐๐ก๐ข๐๐ฏ๐๐ฆ๐๐ง๐ญ ๐จ๐ ๐๐ข๐จ๐ฅ๐จ๐ ๐ข๐๐๐ฅ ๐๐ฏ๐จ๐ฅ๐ฎ๐ญ๐ข๐จ๐ง. ๐๐ฅ๐ฅ ๐ฆ๐๐ฆ๐ฆ๐๐ฅ๐ฌ ๐ก๐๐ฏ๐ ๐ญ๐ก๐ข๐ฌ ๐ฌ๐ฐ๐๐ญ๐ก ๐จ๐ ๐ญ๐ข๐ฌ๐ฌ๐ฎ๐ ๐๐จ๐ฏ๐๐ซ๐ข๐ง๐ ๐ญ๐ก๐๐ข๐ซ ๐๐ซ๐๐ข๐ง, ๐๐ง๐ ๐ญ๐ก๐ ๐ฌ๐ข๐ฑ ๐ฅ๐๐ฒ๐๐ซ๐ฌ ๐จ๐ ๐๐๐ง๐ฌ๐๐ฅ๐ฒ ๐ฉ๐๐๐ค๐๐ ๐ง๐๐ฎ๐ซ๐จ๐ง๐ฌ ๐ฐ๐ข๐ญ๐ก๐ข๐ง ๐ข๐ญ ๐ก๐๐ง๐๐ฅ๐ ๐ญ๐ก๐ ๐ฌ๐จ๐ฉ๐ก๐ข๐ฌ๐ญ๐ข๐๐๐ญ๐๐ ๐๐จ๐ฆ๐ฉ๐ฎ๐ญ๐๐ญ๐ข๐จ๐ง๐ฌ ๐๐ง๐ ๐๐ฌ๐ฌ๐จ๐๐ข๐๐ญ๐ข๐จ๐ง๐ฌ ๐ญ๐ก๐๐ญ ๐ฉ๐ซ๐จ๐๐ฎ๐๐ ๐๐จ๐ ๐ง๐ข๐ญ๐ข๐ฏ๐ ๐ฉ๐ซ๐จ๐ฐ๐๐ฌ๐ฌ. ๐๐ข๐ง๐๐ ๐ง๐จ ๐๐ง๐ข๐ฆ๐๐ฅ๐ฌ ๐จ๐ญ๐ก๐๐ซ ๐ญ๐ก๐๐ง ๐ฆ๐๐ฆ๐ฆ๐๐ฅ๐ฌ ๐ก๐๐ฏ๐ ๐ ๐ง๐๐จ๐๐จ๐ซ๐ญ๐๐ฑ, ๐ฌ๐๐ข๐๐ง๐ญ๐ข๐ฌ๐ญ๐ฌ ๐ก๐๐ฏ๐ ๐ฐ๐จ๐ง๐๐๐ซ๐๐ ๐ก๐จ๐ฐ ๐ฌ๐ฎ๐๐ก ๐ ๐๐จ๐ฆ๐ฉ๐ฅ๐๐ฑ ๐๐ซ๐๐ข๐ง ๐ซ๐๐ ๐ข๐จ๐ง ๐๐ฏ๐จ๐ฅ๐ฏ๐๐.
The brains of reptiles seemed to offer a clue. Not only are reptiles the closest living relatives of mammals, but their brains have a three-layered structure called a dorsal ventricular ridge, or DVR, with functional similarities to the neocortex.
The neocortex stands out as a stunning achievement of biological evolution. All mammals have this swath of tissue covering their brain, and the six layers of densely packed neurons within it handle the sophisticated computations and associations that produce cognitive prowess. Since no animals other than mammals have a neocortex, scientists have wondered how such a complex brain region evolved.
Now, however, by analyzing molecular details invisible to the human eye, scientists have refuted that view. By looking at patterns of gene expression in individual brain cells, researchers at Columbia University showed that despite the anatomical similarities, the neocortex in mammals and the DVR in reptiles are unrelated. Instead, mammals seem to have evolved the neocortex as an entirely new brain region, one built without a trace of what came before it. The neocortex is composed of new types of neurons that seem to have no precedent in ancestral animals.
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