Transcript Slide 1
Brain & Behavior Psych 545
Dr David A Kaiser
Office: Bldg 6 – A116 x6773 [email protected]
www.rit.edu/~dakgsh
Largest Brain on planet, 9.2 kg
Belongs to Sperm Whale
Absolute Brain Weight – Does it reflect intelligence?
Species Chimpanzee Human Bottlenosed dolphin African elephant Fin whale Sperm Whale Adult Brain Weight (grams) 450 1,350 1,600 6,075 7,200 9,200
Relative Brain Weight
Species Human Bottlenosed dolphin Chimpanzee African elephant Killer whale Cow Sperm Whale Brain to Body Weight 2.1 % 1.2 % .7 % .5 % .1 % .08 % .02 %
Encephalization
• Increase in brain size during evolution of SPECIES, with no concomitant increase in body size • “Of all animals, man has the largest brain in proportion to his size” - Aristotle
Encephalization
Encephalization 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 mass • Total Brain Mass = Brain for body size + Residual brain for higher functions
Encephalization Quotient (EQ)
???????? Human Dolphin Killer whale Chimpanzee Rhesus Monkey Elephant Whale Dog Cat Horse Sheep Mouse Rabbit 9.0 7.4 5.6 2.9 2.5 2.1 1.9 1.8 1.2 1.0 0.9 0.8 0.5 0.4
Encephalization Quotient (EQ)
Hummingbird Human Dolphin Killer whale Chimpanzee Rhesus Monkey Elephant Whale Dog Cat Horse Sheep Mouse Rabbit 9.0 7.4 5.6 2.9 2.5 2.1 1.9 1.8 1.2 1.0 0.9 0.8 0.5 0.4
1 g brain for hummingbird
EQ 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?
Evolution of behavioral complexity
Neural arms race in mammalian group only
In all mammalian orders including primates
Neurobehavioral “Arms race”
Monkeys, Great Apes, and Us
Four leaps in braininess
1.
2.
3.
4.
To Primate To Australopithecus To Hominid To Homo sapiens
Brainy Newcomers
Convolution Index = wrinkliness
• BUT: Cortex width: human 2.9 mm, dolphin 1.7 mm and conversative (not progressive) organization
Our “Family”
...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 neanderthalensis Homo sapiens
We shared planet with two other human species as recently as 25,000 years ago – Homo erectus and Neanderthals • Coincided with unstable weather (4 ice ages)
Hominid Australopithecus H habilis H erectus H heidelbergensis H neanderthalensis H sapiens Million yrs Weight (g) 5.0
500
2.5
1.7
0.6
0.2
0.2
725 1000 1200 1500 1350 Can human brain get any bigger?
Encephalization abuse within species
General Features of Brain Evolution
• • • • • • Relative increase in brain size Relative increase in telencephalon (cortex) over midbrain and hindbrain Relative increase in representation of sensory information over motor responses Relative increase in cortex involved in associative integration than (primary) reception Greater differentiation of neocortex, with more cell diversity Relative importance of biophysical senses over chemical senses in more sentient species Convergent evolution in all mammalian groups of these morphophysiological features
Neoteny – Childlike features into adulthood
Bonobo and Common Chimp
What did big brain gives us? Social or Cognitive Intelligence?
• Example of cognitive: Tool Use in Animals , termite fishing by bonobo
Social Intelligence
• The 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.
Dunbar (1992)- natural group size