Tuesday, May 7, 2019

Brain Size and Density by Race

A basic law of biology is that longer infancy is related to greater brain growth.

Blacks are the only race not hybridized with the large-brained Neanderthals, and also the only race without the derived form of MCPH1 microcephalin called haplogroup D which produces increased brain volume.

The correlation between brain size and IQ across 25 primate species is 0.77 (where 1.0 indicates that monozygotic twins have no variance in IQ and 0 indicates that their IQs are completely uncorrelated).
Structural imaging of total brain gray and white matter volumes is perhaps the most obvious approach to correlate brain measures with general intelligence (Toga et al, 2005). Brain structure measured from MRI correlates with intelligence test scores as total brain volume (Gignac et al. 2003), as do the volumes of individual lobes and aggregate gray and white matter volumes (Posthuma et al. 2002).
Larger brains contain more neurons and synapses and process information faster. By adulthood, East Asians average one cubic inch more cranial capacity than Whites who average five cubic inches more than Blacks.

In the commonly used Smith-Beals data set of 20,000 skulls worldwide, East Asians averaged 1415 cubic centimeters of brain volume. Ethnic Europeans averaged 1362 cubic centimeters, and sub-Saharan Africans averaged 1268 cubic centimeters.

Brain Size by Race:
         •   Blacks   =   1267 cm³
         •   Whites   =   1347 cm³
         •   Asians   =   1364 cm³

Brain Weight by Race:
         •   Blacks   =   1261 grams
         •   Whites   =   1387 grams
         •   Asians   =   1374 grams

Whites' brains are faster, larger, denser, and more complex than Blacks' brains:
         •   7% larger
         •   126 grams heavier
         •   deeper fissuration in the frontal and occipital regions
         •   more complex convolutions
         •   larger frontal lobes
         •   more pyramidal neurons
         •   16% thicker supra-grandular layer
         •   one standard deviation more cerebrum
         •   react faster on mental chronometry tests
         •   600 million more neurons

Race differences start in the womb. Blacks are born earlier and grow quicker than Whites and Asians.
Black babies mature more quickly than White babies, while Asian babies mature more slowly. Black babies in a sitting position are more able to keep their heads up and backs straight from the start. White babies often need six to eight weeks to do these things.
Black babies spend the least time in the womb. 51% of Black children have been born by week 39 of pregnancy compared with 33% of White children.
Black children sit, crawl, walk, and put on their own clothes earlier than Whites or Asians. The findings are measured by such tests as Bayley’s Scales of Mental and Motor Development and the Cambridge Neonatal Scales.
Asian children, on the other hand, mature more slowly than do White children. Asian children often do not walk until 13 months. Walking starts at 12 months for white children and 11 months for Black children.

MILESTONE: Being drawn up into a sitting position, able to prevent the head from falling backwards:
         Black: Nine hours
         White: Six weeks
MILESTONE: With head held firmly, looking at the face of the examiner:
         Black: Two days
         White: Eight weeks
MILESTONE: Supporting self in a sitting position and watching own reflection in a mirror:
         Black: Seven weeks
         White: Twenty weeks
MILESTONE: Holding self upright:
         Black: Five months
         White: Nine months
MILESTONE: Climbing the steps alone:
         Black: 11 months
         White: 15 months

"...the kinesthetic maturation rate of Black infants was two or three times that of White children." Simpson, 2003
Faster maturation goes along with a shorter life span. In 2002, Black Americans had 40.5% more deaths than they would have had with the White mortality rate.
A 2005 report by former U.S. Surgeon General David Satcher: The bodies of Blacks mature faster.
İşcan, 1987; Wilson, 1978; Levin, 1997; Freedman, 1969.

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