Cranial capacity: can it indicate high IQ?

His name was Ettore Majorana.

Ettore Majorana was an Italian theoretical physicist who worked on neutrino masses. On 25 March 1938, he disappeared under mysterious circumstances while going by ship from Palermo to Naples. The Majorana equation and Majorana fermions are named after him. In 2006, the Majorana Prize was established in his memory.

Occipital buns were common in Neanderthals, but seem to also be quite more frequent among rh negatives than the common population where it is seen as a very rare phenomenon.

The question is why so many of those who have it are similar to the guy above:

Above or far above average intelligence.

It seems the brain needed extra space. We have already shown that Neanderthals were more advanced than modern humans during their time.

Is your cranial capacity high? Do you have an occipital bun?

How high is your IQ?

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2668913/

The preponderance of evidence demonstrates that brain size is correlated positively with intelligence and that both brain size and GMA are correlated with age, socioeconomic position, sex, and population group differences. Correlation does not prove cause, but, just as zero correlations provide no support for a hypothesis of cause and effect, nonzero correlations do provide support. The brain size/GMA relation has been established both within and between species and brain size has shown a progressive trend upwards for 570 million years.

https://www.ncbi.nlm.nih.gov/pubmed/526851

The relationship between brain size and intelligence was investigated in two ways. Cranial capacity was measured in people with known IQs. A very small correlation was found between cranial capacity and intelligence; but this was shown to be the result of the confounding effects of height. A large series of brains was also investigated, data being obtained on occupation from the case notes. When the effects of body height and weight were controlled for, it was possible to demonstrate a statistically significant, but very slight, relation between brain size and occupational group.