Brain expansion: an article says designed differently (Evolution)

by David Turell @, Saturday, July 18, 2020, 05:41 (28 days ago) @ David Turell

Our brain is not only much bigger than apes, it is designed very differently and cannot be considered an expected advance from previous designs:

https://www.sciencedirect.com/science/article/pii/S0896627314000105?dgcid=raven_sd_reco...

"Programmed to be Human?

"Pletikos et al. (2014) demonstrate in this issue of Neuron that the human neocortex has an “hourglass” temporal gene expression pattern with robust and dynamic transcriptome differences during the prenatal and adolescent/adult periods. Similar changes are not observed in the nonhuman primate—is this what makes us human?

"Perhaps the biggest marvel of nature is the development of the human brain. It is estimated that an average human brain has ∼86 billion neurons, >100 trillion synapses, and >100,000 miles of myelin-covered nerve fibers (Pakkenberg and Gundersen, 1997, Pakkenberg et al., 2003). The final organization of this immensely complex structure is dependent on merely 20,000 protein-encoding genes, 23 pairs of chromosomes, and four nucleotide bases. Yet, the final product of development, the human brain, is a tridimensional jigsaw puzzle, made up by thousands of different kinds of projection neurons, local circuit neurons, and glial cells. They are arranged in elaborate neural networks, serve special functions, and lead to a unique condition of being human. The anatomical, neurochemical, and physiological differences across the different brain regions are tremendously complex, and the patterning and development of such an intricate system has been the focus of intense research endeavors for more than a century.

"A particular characteristic of neocortical tissue is the precise specification and coordinated development of brain regions. Although this basic neocortical map is shared among mammals, there are multiple, unique organizational differences that are a hallmark of the human brain.

***

"These patterns of gene expressions were, at least partially, unique to the human brain, as quantitative PCR studies revealed that the interareal expression pattern of a set of selected genes was not very well correlated between the healthy human and the nonhuman primate brains. This raised the possibility that the developmental program responsible for the precise patterning of the brain is species specific. In other words, individual transcripts appear to act as common building blocks of the brain and it is their species-specific regulation that makes the brain of any species, including humans, unique. (my bold)

***

"Thanks to early seminal work by Broca, Wernicke, Sperry, and Geschwind, it is clear that the functional differences between the left and the right brain are even more striking than the anatomical differences (Hugdahl, 2005). For example, speech is a clearly lateralized, uniquely human process, and handedness is also a hemisphere-encoded process...The symmetric interareal transcriptome in this study from the Šestan group will spur the field to identify the factors that establish this critical feature of the human neocortex.

***

"After all, we are a unique species, and for understanding our own individual phenotypic variability, we must first decipher what is specific about Homo sapiens."

Comment: This article and the previous one sound almost like ID sourced material or commentary from Adler. The size and organization of our brain is a giant leap from the previous brains from which we were evolved. A typical non-Darwinian gap in the evolution story .


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