9Encephalization Quotient (EQ) Anatomical estimate of species’ intelligence (non-behavioral)EQ = ratio of brain weight of animal to brain weight of “typical” animal of same body weight (Jerison, 1973)EQ represents index of residual value of brain massTotal Brain Mass = Brain for body size+ Residual brain for higher functions
10Encephalization Quotient (EQ) ????????9.0Human7.4Dolphin5.6Killer whale2.9Chimpanzee2.5Rhesus Monkey2.1Elephant1.9Whale1.8Dog1.2Cat1.0Horse0.9Sheep0.8Mouse0.5Rabbit0.4Human neocortex is 3.2x larger in volume than nonhuman primate with our body size (Jerison, 1973).Overview QuizTLE
11Encephalization Quotient (EQ) Hummingbird9.0Human7.4Dolphin5.6Killer whale2.9Chimpanzee2.5Rhesus Monkey2.1Elephant1.9Whale1.8Dog1.2Cat1.0Horse0.9Sheep0.8Mouse0.5Rabbit0.41 g brain for hummingbirdHuman neocortex is 3.2x larger in volume than nonhuman primate with our body size (Jerison, 1973).Overview QuizTLE
12EQ through evolutionary time Are we evolving into smarter and smarter creatures? Or was humanity a fluke?In other words, was there a neural arms race in the past or an unusual mutation process in one line of primates?Human neocortex is 3.2x larger in volume than nonhuman primate with our body size (Jerison, 1973).Overview QuizTLE
13Evolution of behavioral complexity Neural arms race in mammalian group only
22...And Then There Was One Sixteen Species of Extinct Humans Ardipithecus ramidus Australopithecus anamensis Australopithecus afarensis Australopithecus bahrelghazali Australopithecus aethiopicus Paranthropus boisei Paranthropus robustus Australopithecus africanus Australopithecus garhi Homo rudolfensis Homo habilis Homo ergaster Homo erectus Homo antecessor Homo heidelbegensis Homo neanderthalensisHomo sapiens
23We shared planet with two other human species as recently as 25,000 years ago – Homo erectus and NeanderthalsCoincided with unstable weather (4 ice ages)
25Can human brain get any bigger? HominidMillion yrsWeight (g)Australopithecus5.0500H habilis2.5725H erectus1.71000H heidelbergensis0.61200H neanderthalensis0.21500H sapiens1350Can human brain get any bigger?
27General Features of Brain Evolution Relative increase in brain sizeRelative increase in telencephalon (cortex) over midbrain and hindbrainRelative increase in representation of sensory information over motor responsesRelative increase in cortex involved in associative integration than (primary) receptionGreater differentiation of neocortex, with more cell diversityRelative importance of biophysical senses over chemical senses in more sentient speciesConvergent evolution in all mammalian groups of these morphophysiological features
33What did big brain gives us? Social or Cognitive Intelligence? Example of cognitive: Tool Use in Animals , termite fishing by bonobo
34Social IntelligenceThe Machiavellian Hypothesis – Richard Alexander (1970s) suggested that main evolutionary pressure behind human intelligence was competition with other people, notably sexual competition between individuals of the same sex.