Alien Physiology,
Convergent Evolution,
and fc
Recap
N = N* fs fGHZ fp nH fl fJ fƒfEufm fi fc L/T
• N* = 4 x 1011
• fs = 0.2
• fGHZ = 0.002
• fp = 1.0
• nH = 2
• fl = 1.0
• fJ = 0.5
• fƒ = 0.01
• fEu = 0.1
• fm = 0.1
• fi = 0.3
N = 4.8 x 103
Necessities of Life
•  Energy
–  What does it eat?
–  How does it eat?
•  Reproduction
•  Senses
–  What senses are important?
–  Communication
•  Motility
Convergent 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.
Will Intelligent Aliens be
Humanoids?
What might a Martian look
like?
Let’s build an alien…
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)?
Technology and Culture
• Must intelligent life form societies, and have cultures?
• Some insects are social, and keep farms.
• Many mammals, and most primates, are social.
• Is a society required for the development of
technology?
• Some primates and birds use tools.
N update
N = N* fs fGHZ fp nH fl fJ fƒfEufmfifc L/T
• N* = 4 x 1011
• fs = 0.2
• fGHZ = 0.002
• fp = 1.0
• nH = 2
• fl = 1.0
• fJ = 0.5
• fƒ = 0.01
• fEu = 0.1
• fm = 0.1
• fi=0.3
• fc=0.1
N = 480