Variation of the cranial capacity of current humans

The variation of the cranial capacity of current humans is relevant information for those interested in the debates about human evolution. It is normal to be presented to the reader the average capacity of each species. For example, the average capacity of Homo sapiens is around 1,350 c.c. However, variation is another important piece of information, since if we have a large variation, then other species of the genus Homo appear included within the variation of Homo Sapiens.

Variation range
Statements about the variation of cranial capacity in modern humans show variation, but in general, it is observed that this variation is very large. According to Ralph Holloway "The range of variation of cranial capacity for modern Homo Sapiens is about 1.000 c.c., with no correlation between capacity and behaviour readly demonstrable." Shara E. Bailey agrees with this variation in noting that "on average, the cranial capacity of Homo erectus was about 900 c.c., although its range (750 c.c.–1250 c.c.) overlaps that of modern humans (1000 c.c.–2000 c.c.)" that is, the same variation of 1,000 c.c. Greg Beasley reports an even greater range (minimum 1200 c.c.) with capacity ranging from 800 to 2000 c.c. Doctor David Menton states that "the size of the normal adult human brain varies by almost three times". Beasley cites several proposed ranges in his article that have been included in the box below.

Cranial capacities greater than 2,000 c.c.
Cranial capacities that are beyond Dillon's provisional range have been documented in scientific journals. According to Greg Beasley there have only been three recorded determinations greater than 2000 c.c. - these being the Russian novelist Turgenev (2,021 c.c.), a United States senator, and a low-IQ person - the latter two being of equal capacity (2,800 cc). Stephen Molnar cites two examples of famous men who had their brains weighed and measured with a cranial capacity of approximately 2,200 c.c.: Oliver Cromwell and Lord Byron.

Lower capacities
At the lower end of the Dillon range are the Wedda Pygmies of Sri Lanka. However, there is an example of an Australian Aboriginal adult with 830 c.c. In none of these cases are these people described in any way as having incompetent or subnormal intellect. More recently, several authorities have suggested lower values for a "cerebral rubicon" (Vallois, 800 c.c.; Robinson, 750 c.c. e Weidenreich, 700 c.c.). Javier deFelipe quoting B. G. Wilder presents an example of a normal person with a very small brain, such as the case of Daniel Lyons who died in 1907 at the age of 41. Daniel was a person with no special features, with normal body weight and normal intelligence, although his brain weighed no more than 680 g. According to Rupe and Sanford, Anatole France was the winner of the Nobel Prize for Literature and his cranial capacity was 933 cm3 - the same size as many Erectus specimens such as the Java man and Turkana boy. According to Rupe and Sanford, a man named Daniel Lyon had a cranial capacity of 624 cm3 (680 grams) and worked at the Pennsylvania railroad terminal for 20 years being able to read and write without showing any signs of mental impairment.

Large cranial capacities in ancient humans
Two early Late Pleistocene skulls from Lingjing, Xuchang, China, show primitive features of Homo erectus pekinensis, or Peking Man, including low neurocranial dome, smooth and short inward-sloping mastoid neurocranium while sharing ascribed features to Neanderthal man as occipital (suprainac and nuchal torus) and labyrinthine temporal (semicircular canal) morphology. The endocranial volume (ECV) of Xuchang 1, ~1800 cm3, is at the upper end of modern and Neanderthal human variation.