1. Largest Brain on planet, 30 lbs!

2. Belongs to Sperm Whale

3. Absolute Brain Weight – Does it reflect intelligence?
Species
Adult Brain Weight (grams)
Chimpanzee
450
Human
1,350
Bottlenosed dolphin
1,600
African elephant
6,075
Fin whale
7,200
Sperm Whale
9,200

4. Relative Brain Weight Of all animals, man has the largest brain in proportion to his size” - Aristotle
Species
Brain to Body Weight
Human
2.1 %
Bottlenosed dolphin
1.2 %
Chimpanzee
0.70 %
African elephant
0.50 %
Killer whale
0.10 %
Cow
0.08 %
Sperm Whale
0.02 %

5. Encephalization: Increase in brain size during evolution of SPECIES, with no concomitant increase in body size

6. Encephalization Quotient (EQ)
????????
9.0
Human
7.4
Dolphin
5.6
Killer whale
2.9
Chimpanzee
2.5
Rhesus Monkey
2.1
Elephant
1.9
Whale
1.8
Dog
1.2
Cat
1.0
Horse
0.9
Sheep
0.8
Mouse
0.5
Rabbit
0.4
Anatomical estimate of species’ intelligence based on brain/body size and not behavior
EQ = ratio of brain weight of animal to brain weight of “typical” animal of same body weight
EQ represents residual value of brain mass
Human neocortex is 3.2x larger in volume than nonhuman primate with our body size (Jerison, 1973).
    
Overview Quiz
TLE

7. Encephalization Quotient (EQ)
Hummingbird
9.0
Human
7.4
Dolphin
5.6
Killer whale
2.9
Chimpanzee
2.5
Rhesus Monkey
2.1
Elephant
1.9
Whale
1.8
Dog
1.2
Cat
1.0
Horse
0.9
Sheep
0.8
Mouse
0.5
Rabbit
0.4
         
1 g brain for hummingbird
Human neocortex is 3.2x larger in volume than nonhuman primate with our body size (Jerison, 1973).
    
Overview Quiz
TLE

8. 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?
Human neocortex is 3.2x larger in volume than nonhuman primate with our body size (Jerison, 1973).
    
Overview Quiz
TLE

9. Evolution of behavioral complexity
Neural arms race in mammalian group only

11. Four leaps in braininess
To Primate
To Australopithecus
To Hominid
To Homo sapiens

12. Brainy Newcomers

13. Convolution Index = wrinkliness
BUT: Cortex width: human 2.9 mm, dolphin 1.7 mm and conversative (not progressive) organization

15. Not a straight ascent to modern humans
Coincided with unstable weather (4 ice ages)

16. ...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

17. Sensory information is processed subcortically, and then first is processed cortically in primary modality areas

19. Primary versus Association Cortex
BUT the dolphin brain is organized differently

20. General Features of Encephalization
Increase in absolute & especially relative brain size
Cortex enlarged compared to lower structures
More brain tissue for sensory functions compared to motor functions
Increase in Associative areas
Rise of importance of biophysical senses compared to chemical senses

21. Mammals: Smell, Sight, or Sound Brains
% volume
Rat
Human
Cortex 31 77
Midbrain 13 8
Brainstem 7 2
Cerebellum 10
Spinal cord 35
Number of olfactory receptor cells
Human 40 Million
Rabbit 100 M
Dog M

22. Hominid
Million yrs
Weight (g)
Australopithecus
5.0
500
H habilis
2.5
725
H erectus
1.7
1000
H heidelbergensis
0.6
1200
H neanderthalensis
0.2
1500
H sapiens
1350
Can human brain get any bigger? Perhaps, but need to consider speciation, torque, and pelvic evolution.