Intelligence N to date

N = N* fs fGHZ fp nH fl fJ ffEufm 11 •N* = 4 x 10 •fs = 0.2 •fGHZ = 0.1 •fp = 0.8 •nH = 2 •fl = 1.0 •fJ = 0.5 •f = 0.01 •fEu = 0.1 •fm = 0.1

N = 6.4 x 105 Fi

The fraction of times that life evolves intelligence

What is intelligence?

Is there evolutionary pressure for the evolution of intelligence? Costs of Intelligence

Intelligence is biologically expensive

It requires lots of energy: The human brain requires about 25% of our resting metabolism; the primate brain requires about 8% of resting metabolism; the mammalian brain requires about 4% of resting metabolism.

It requires nurturing

Does it requires societies? Does Intelligence Equal Success?

What is evolutionary success?

If intelligence is adaptive, why did it evolve so late?

Dinosauria never became intelligent, nor have birds A Pessimistic View

Life has been on Earth for 3.8 Gyr

Intelligence (self-cognition) evolved only within the past million years or so (1/3800 = .00026 of available time).

Earth will become uninhabitable within another 1 Gyr

Intelligence has evolved within the last (<)20% of Earth’s habitability.

If Earth is typical, in many cases intelligence will not evolve while the planet is habitable. (see http://www.sciencedaily.com/releases/2008/04/080416110124.htm) Encephalization Quotient

Larger animals tend to have larger brains.

Allometry (the science of the relation between size and shape) can be used to sketch general trends.

The predicted brain mass for an animal of mass W is BM = 1.77 * W0.76 The Encephalization Quotient EQ is the actual brain mass relative to the predicted brain mass Encephalization Quotient Encephalization Quotients Species EQ Man 7.44 Dolphin 5.31 Chimpanzee 2.49 Rhesus Monkey 2.09 Elephant 1.87 Whale 1.76 Dog 1.17 Cat 1.00 Horse 0.86 Sheep 0.81 Mouse 0.50 Mouse 0.50 Rabbit 0.40 fi fi = 1? On a random sample of planets, maybe fi = 0.1 Covergent Evolution •Evolutionarily useful traits evolve among unrelated animals.

•Manipulative organs: •Primate hands •Bird beaks •Elephant trunks •Cephalopod tentacles

•The eye has evolved >65 times, with 10 different designs. • The mammalian eye evolved from brain tissue. • The cephalopod eye evolved from skin tissue. Intelligent Aliens What might they look like?

They probably have sense organs What senses?

They probably have manipulative organs What kind? How many?

They probably move about How?

A lot will depend on the planet’s gravity and temperature. Technology

If we expect to make contact and communicate, (unless we can travel to their planet), they must have communications technology (e.g., radio) fc is fraction of intelligent creatures that develop communications technology Intelligence and Technology

Must intelligent creatures develop technology?

Can you generate technology without manipulative organs (e.g., hands)?

Some primates and birds use tools.

Some insects are social, and keep farms. N update

N = N* fs fGHZ fp nH fl fJ ffEufmfifc 11 •N* = 4 x 10 •fs = 0.2 •fGHZ = 0.1 •fp = 0.8 •nH = 2 •fl = 1.0 •fJ = 0.5 •f = 0.01 •fEu = 0.1 •fm = 0.1 •fi=0.1 •fc=0.3 N = 19,000 Uncertainties on N

N = N* fs fGHZ fp nH fl fJ ffEufmfifc 11 •N* = 4 x 10 ± 25% •fs = 0.2 ± 0.1 •fGHZ = 0.1 +0.2, -0.05 •fp = 0.8 ±0.2 •nH = 2 ±1

•fl = 1.0 +0, -0.99 •fJ = 0.5 +0.3,-0.5 •f = 0.01 +0.1, -0.01 •fEu = 0.1 +0.9, -0.1 •fm = 0.1+0.9, -0.1 •fi=0.1 +0.9, -0.1 •fc=0.3 +0.7, -0.3 N = 19,000 (from 1 (us) to 1.1x1011)