Brain volume of the newly-discovered species Rhynchocyon udzungwensis (Mammalia: Afrotheria: Macroscelidea): implications for encephalization
Lee, "Ecology and energetics of encephalization
in hominid evolution," Philosophical Transactions of the Royal Society of London B, vol.
Body size, body proportions and encephalization
in a middle Pleistocene archaic human from Northern China.
In the first-ever comprehensive analysis of its kind, a study guided by psychologist Lori Marino used computed tomography to investigate the pattern of encephalization
in some fossil cetacean species in the past 47 million years, and analyzed these data along with those for some modern species.
This led to a measure called the encephalization
quotient (eQ) that permitted a comparison across species of actual, observed brain sizes versus those that would be predicted purely on the basis of body size.
This and progressively increasing brain size (encephalization
) in hominids led to the present human obstetrical dilemma: larger offspring with larger brains in the presence of a narrow pelvis that favors Bipedalism.
The pattern of human evolution: studies on bipedalism, mastication and encephalization
. Annu Rev Anthro.
IN BIOLOGY, SCIENTISTS SPEAK OF "ENCEPHALIZATION
," the growth of relative brain size of a species as it evolves.
Complex adaptations tend to evolve gradually (Dawkins, The Blind Watchmaker; and Williams), and the trend toward encephalization
is no exception.
This process, known as encephalization
, required changes in diet and physiology as such big brains need higher quality food such as meat.
In this example of "encephalization
of function" (Jackson 1925; Ferrier 1876; Karten 1991; Aboitiz 1993; Striedter 1997) motor operations are increasingly "taken over" by cortex as the size of the pyramidal tract overtakes that of the descending striatal system.