Cranial Capacity

Cranial capacity is a measure of the volume of the interior of the cranium (also called the braincase or brainpan or skull) of those vertebrates who have both a cranium and a brain. The most commonly used unit of measure is the cubic centimetre or cc. The volume of the cranium is used as a rough indicator of the size of the brain, and this in turn is used as a rough indicator of the potential intelligence of the organism. However, larger cranial capacity is not always indicative of a more intelligent organism, since larger capacities are required for controlling a larger body, or in some cases are an adaptive feature for life in a colder environment.

Neurological functions are determined more by the organization of the brain rather than the volume. Individual variability is also important when considering cranial capacity, for example the average Neanderthal cranial capacity for females is 1300 cc and 1600 for males (Stanford, 2009, 301). In an attempt to use cranial capacity as an objective indicator of brain size, the encephalization quotient (EQ) was developed in 1973 by Harry Jerison. It compares the size of the brain of the specimen to the expected brain size of animals with roughly the same weight (Campbell et al., 2006, 346). This way a more objective judgement can be made on the cranial capacity of an individual animal.

Examples of cranial capacity:

• Orangutans: 275–500 cc
• Chimpanzees: 275–500 cc
• Gorillas: 340–752 cc
• Humans: 1000–1900 cc
• Neanderthals: 1200–1900 cc

Examples of early hominids:

A large scientific collection of brain endocasts and measurements of cranial capacity has been compiled by Holloway et al. and is publicly available, but is not yet reflected in the above tables.