Cranial capacity is not related to intelligence. People in Britain and Japan have similar cranial capacity as people living in North Africa. Also Japanese (who are genetically very similar to Chinese) have a different cranial capacity than Chinese people
(archive.is)https://archive.is/SxJhqsource:
https://booksc.org/book/64009679/d07e74Groups with large
volumes per unit of mass include San (33.4 cm3 per kg), Andamanese (27.6), and Bengali (27.8). Groups with small volumes per unit of mass include Choctaw (20.8), French (22.0),
Mapuchi (22.1), and Maori (22.1). An overall relation between
cranial capacity and body mass is clear from these examples
From a structural perspective, the greatest contribution
to volume is from breadth. Different populations have different
cranial geometries. Most simply stated, some groups have larger
brains than others because their heads are rounder. Arctic peoples obtain large capacities not so much from large heads as
from a more globular shape.
The distribution indicates that racial means are actually reflections of
secondary correlation with climate. For example, Native Americans have a common ancestry but almost the entire range of
variation in cranial capacity
