- Encephalization
Encephalization is defined as the amount of
brain mass exceeding that relatedBrain to body mass ratio . Quantifying an animal's encephalization has been argued to be directly related to that animal's level of
to an animal's total body massintelligence . In fact, as early as 1871,Charles Darwin wrote in his book "The Descent of Man": "No one, I presume, doubts that the large proportion which the size of man's brain bears to his body, compared to the same proportion in the gorilla or orangutan, is closely connected with his mental powers."Williams [ [http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6WN2-45WYMG6-9&_coverDate=04%2F30%2F2002&_alid=345187568&_rdoc=1&_fmt=&_orig=search&_qd=1&_cdi=6950&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=cb9acecb46bd950701b34eb5bb5e94ee Primate encephalization and intelligence - M. F. Williamsf1 - Oakland, USA] ] has recently argued that the most accurate means for quantifying the encephalization of humans and other adult primate species requires the use of Lapicque's universal exponent of 0.28 in Snell's equation of simple
allometry . Since Lapicque's slope was derived from various vertebrate groups, this equation may potentially be universally applicable for determining relative adult vertebrate encephalization and intelligence.Encephalization may also refer to the tendency for a species toward larger brains through evolutionary time. Anthropological studies indicate that bipedalism preceded encephalization in the human evolutionary lineage after divergence from the
chimpanzee lineage. Compared to the chimpanzee brain, the human brain is larger and certain brain regions have been particularly altered during human evolutionref|compchimp. Most brain growth of chimpanzees happens before birth while most human brain growth happens after birth [ see:Heterochrony ] .In 2004,
Dennis Bramble andDaniel Lieberman proposed that early "Homo" were scavengers that used stone tools to harvest meat off carcasses and to open bones. They proposed that humans specialized in long-distance running to compete with other scavengers in reaching carcassesref|running. It has been suggested that such an adaptation ensured a food supply that made large brains possible.More encephalized species tend to have longer
spinal shock duration.References
On-line
# See Figures 1 and 2 of "Molecular insights into human brain evolution." by J. Bradbury in "PLoS Biology" (2005) volume 3 page e50. ( [http://www.pubmedcentral.gov/articlerender.fcgi?tool=pubmed&pubmedid=15760271 Full text online] )
# "Endurance running and the evolution of Homo" by D. M. Bramble and D. E. Lieberman in "Nature" (2004) volume 432 pages 345-352. Entrez Pubmed|15549097Other
* Williams MF., "Primate encephalization and intelligence". Med Hypotheses. 2002 Apr;58(4):284-90.
* Jerison H. J. "Paleoneurology and the evolution of the mind". Scientific American 1976; 234: 90-101.
* Tobias P. V. "The Brain in Hominid Evolution". New York and London: Columbia University Press, 1971.ee also
*
Cephalization
*Human evolution
*Human brain
*Aquatic ape
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