Big brain evolution: brain size and intelligence (Evolution)

by David Turell @, Tuesday, March 20, 2018, 23:28 (274 days ago) @ David Turell

Current studies show that the level of intelligence depend on volume and complexity: :

If specific features of brain structure are under strong genetic control, investigators should determine whether any of these features are correlated with intelligence. If so, this correlation may not only reveal why IQ has repeatedly been found to be highly heritable, but also yield insight into possible neural mechanisms. To help understand this approach, we first review evidence that brain structure and intelligence are correlated before discussing evidence for the existence of genetic correlations between brain structure and intelligence (which means that the same sets of genes are implicated in determining both; Posthuma et al. 2002). A recent meta-analysis (including a total of 1375 subjects) found that total brain volume and IQ were correlated significantly in all but 1 of 28 MRI studies, with an estimated correlation of 0.33 (McDaniel & Nguyen 2002). This finding implies that ∼10% of the population variability in IQ can be predicted from brain volume measures alone. Some studies have quoted slightly higher figures for these correlations (e.g., 0.41; Andreasen et al. 1993), and the exact value obtained will depend on the measurement error of the technique because measurement errors will tend to diminish any observed correlation (relative to the true correlation). Linkages between brain structure and IQ also can be further localized by parcellating the brain into subregions or by creating maps of the correlations between gray matter and IQ. Recently, we found that intellectual function (g) was significantly linked with differences in frontal gray matter volumes, which were determined primarily by genetic factors (Thompson et al. 2001a). Posthuma et al. (2002) extended these findings using a cross-twin cross-trait (bivariate genetic) analysis to compute genetic correlations. They demonstrated that the linkage between gray matter volumes and gray matter volumes is mediated by a common set of genes. Haier et al. (2004) used voxel-based morphometry in two independent samples to identify substantial gray matter correlates of IQ. More gray matter was associated with higher IQ in all lobes, underscoring a distributed model of the neural basis of intelligence. Intriguingly, the strongest correlations are typically found between IQ and frontal gray matter volumes (Thompson et al. 2001a, Haier et al. 2004), the same brain regions that are under greatest genetic control. Frontal brain regions play a key role in working memory, executive function, and attentional processes, and their structure has rapidly expanded in recent primate evolution, consistent with their role in reasoning and intellectual function.

Comment: Copied intact. It is logical to assume that advanced intelligence will produce advanced planning and concepts. Erectus did not have the IQ of sapiens. Note that IQ depends upon volume as well as complexity. On this basis I find your theory of enlargement of the human brain to have no basis in fact or theory. There is no evidence that lesser IQ brain produces the more advanced concepts found in greater IQ brain. Our artifacts, produced from concepts which appeared 300,000 years after our brain appeared is consistent with that. Advanced concepts require the presence of more volume and advanced complexity, without question.

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