Origin of Brachycephaly

[Hamlet]

Virtually all early hominid skulls dug up are dolichocephalic. Both the Neanderthal and Cro-Magnon skulls are dolichocephalic - the main two contributors to the European race. How did brachycephaly come about? There is a correlation, between the cephalic index of a race and that race's IQ (the higher the cephalic index, the higher the IQ) - here's how. Brachycephalic skulls have a greater cranial capacity (1520cc) compared to mesocephalic (1475cc) and dolichocephalic skulls (1403 cc), and this in turn correlations strongly with brain size (1181 cc, 1144 cc and 1135cc respectively). This in turn correlates with IQ, as you can see from the graph below (for general races).

My question - as brachycephalic humans are, on the whole, as established, smarter, would it be fair to say that, as early hominids were almost exclusively dolichocephalic, what makes us humans smarter is that the more brachycephalic early hominids were smarter, and thus, according to the general rule of natural selection, survived, and reproduced (and then the brain size would have shrunken, as it has in the last several millenia (for some reason)).



Here are probably the most heralded German philosophers in history - all of whom are brachycephalic.



EDIT: I understand Europe lacked brachycephaly until, relatively speaking, very recently, however the point still stands - where did brachycephaly come from, and why?

[Not a Cop]

Western H-G, aka Cromagnids had much bigger cranial capacity than modern humans yet were dolichocephalic.

[Hamlet]

Western H-G, aka Cromagnids had much bigger cranial capacity than modern humans yet were dolichocephalic.

Agreed, but that does not contradict my point. When they become more brachycephalic, their cranial capacity would have increased. However, as you correctly point out, modern humans have a far lesser cranial capacity. That is why I mentioned how "the brain size would [then] have shrunken, as it has in the last several millenia (for some reason)." Our brains are shrinking even to this day, and there are various theories, but, genetically speaking, nobody really knows why.

[Not a Cop]

Agreed, but that does not contradict my point. When they become more brachycephalic, their cranial capacity would have increased.

Not really, for example if brachycephalisation would've been caused by decrease of head length, CC would've decreased, if by increase of width CC would've increased.

[Hamlet]

Not really, for example if brachycephalisation would've been caused by decrease of head length, CC would've decreased, if by increase of width CC would've increased.

Both would have occurred, but, "given a cavity of oval or elliptical form with elastic walls, the more its contents are increased the greater will be the tendency to assume a spherical shape."

[Hamlet]

I suppose it may be an oversimplification, but brachycephalic humans have a wider but shorter skull (and brain), so, looking at the image below, those with brachycephaly would have larger frontal lobes, however they would also have shorter occipital lobes. This means that whilst the decrease in size of the occipital lobe would result in a lesser spatial intelligence, the increase in size of the frontal lobe would result in a greater verbal intelligence (I am aware of the many exceptions to this rule, such as the fact that Mongoloids have a smaller occipital lobe, yet have a greater spatial intelligence, but, in general, the rule applies).

[Linebacker]

Brachycephaly is progressive,it didn't originate,it evolved.

Cro-Magnon men evolved at some point(probably during Mesolithic) to have broader heads with less length.

[rojos94]

[Stimpy]

Brachycephaly is progressive,it didn't originate,it evolved.

Cro-Magnon men evolved at some point(probably during Mesolithic) to have broader heads with less length.

What's progressive or not is kind of vague. Almost all ancient human remains found were dolichocephalic but then again many apes are brachycephalic.

I think large amounts of brachycephaly came to Europe with near-eastern migrations. Skull shape has always varied a bit though.

[rojos94]

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