Final answer:
The correlation between larger skulls and larger brains on an individual level is not absolute due to factors like genetics and brain organization. The brain's complexity and internal structures play a more significant role in cognitive abilities than size alone.
Step-by-step explanation:
The assumption that a larger skull equates to a larger brain on an individual level is not necessarily accurate. While encephalization (the progressive increase in brain size over evolutionary time) has occurred in the genus Homo, this does not mean that within a species, especially Homo sapiens, a larger skull will always house a larger brain. There are several factors at play, including genetics, developmental biology, and the fact that brain organization can affect cognitive abilities rather than just size.
It is important to consider the concept of the encephalization quotient (EQ), which is a measure of brain size relative to body size. However, researchers are also interested in the brain's cortical neuron density and the complexity of neural connections. These may provide a better correlation with intelligence than mere brain size. This can be illustrated by the fact that Neanderthals had larger brains than modern humans but were not necessarily more intelligent, possibly due to differences in brain organization and development of cognitive abilities. In essence, it's the brain's internal architecture and capacity for complex neural interconnections that largely underpin intelligence, rather than just overall size.