Road Map

1
Road Map

• Evolution
• variation selection adaptation
• example LDH in killifish
• Evolved behaviors
• Tropisms in bacteria fruit flies
• Gibbon songs
• Instinctive learning
• Zebra finches, humpback whales
• Culture as evolution?
• memetics vs. genetics
• arguments pro and con
• Evolution of group behavior
• Genetic
• Cultural

2
Genetic variation and adaptation

• Genetic variation is ubiquitous
• Is a variant worse, neutral or better?
• often this depends on the environment
• Including the attitudes of conspecifics
• In a given environment
• some variants may be selected for
• i.e. produce more offspring
• Result the population adapts to the environment
• (though much variation is selectively neutral
• The population is (part of) the environment
• so the population adapts to interact with itself
• especially
• in social species
• mating behavior

3
Adaptation in Fundulus Heteroclitus (Mummichog)

• Also known as killifish
• 5-7 inches, olive green to blue back, white
  belly
• Lives in salt marshes and tidal creeks
  from Labrador to Mexico

4
LDH

• Lactate dehydrogenase
• Enzyme that catalyzes conversion of lactate to
  pyruvate
• A key step in energy production in living things
• Often the limiting factor in speed or endurance

5
LDH variants

• All enzymes have varying effectiveness at
  different temperatures
• Some variants work better at lower temperatures,
  some work better at higher temperatures
• Fish are cold-blooded, so their body temperature
  depends on the water temperature
• Mummichog genetic LDH variants
• vary in effectiveness at different temperatures
• are selected according to location (I.e.
  temperature)
• result adaptation to different environments

6
Mummichog LDH efficiency
The mummichog B locus for lactate dehydrogenase
(LDH) has two common alleles, LDH-Ba and LDH-Bb.
Catalytic efficiency varies with temperature
the bb genotype wins at lower temperatures,
while the aa genotype wins at higher
temperatures.
7
Mummichog LDH geography
In the Gulf of Maine, nearly all mummichogs have
the genotype bb at the LDH-B locus. Off South
Carolina, the aa genotype rules. In between,
its in between.
8
Adaptation can be rapid

• In Long Island Sound, the aa (warm-water)
  genotype has an overall frequency of 15
• But for Mummichogs living in the thermal effluent
  of a power plant, aa frequency is 30.
• Efficient adaptation to environmental variation
  a mummichog micro-habitat
• Number of generations lt20
• Like beak variation among Darwins Finches on the
  Galapagos Islands
• major adaptation to climate change in lt5
  generations

9
Bacterial taxis

• Taxis ability to move in a desired direction
• Phototaxis towards or away from light
• Chemotaxis towards or away from chemicals
• Magnetotaxis with respect to magnetic field
• Simple but important behavior
• finding food
• avoiding harm
• In colonial and multicellular creatures,
• chemotaxis is crucial in creating structures
• (morphogenesis)

10
Basic mechanisms of bacterial taxis

• Alternation of (straight-line) runsand
  (random) tumbles
• 3D random walk animation
• attractants bind a chemoreceptorthat increases
  time between tumbles
• repellants decrease time between tumbles
• About 40 genes in the basic system
• plus additional genes for new sensors
• Can orient towards or away from
• nutrients, poisons, oxygen, light, pH,
  temperature, etc.
• Categories (which chemicals? which wavelengths?
  etc.) and responses (towards or away?)
  evolve adaptively

11
Rhodospirillum centenumlikes it warm and dark
12
Tropisms in higher organisms

• Mechanisms are more complex
• (and largely unknown)
• Result is similar
• attraction towards some things
• repulsion from others
• Such preferences may be learned
• by individuals what we normally think of as
  learning
• by (sub-)species through genetic variation and
  selection leading to adaptation

13
Natural behavior variation in Drosophila
Melanogaster

• Fruit flies show natural variation in preferences
• Pupae hatching in experimental habitat maze
• separated themselves on four dimensions of
  preference
• up/down
• light/dark
• acetalldehyde/ethanol
• time of the day of emergence (early/late)
• 16 preference combinationsend up in different
  places in the maze

14
(Un)natural selectionleads to speciation!

• Two opposite strains were mated for 25
  generations
• early/up/dark/acetaldehyde vs.late/down/light/eth
  anol
• Result reproductive isolation and habitat
  specialization
• Conclusion behavioral preferences were
  genetically mediated

15
Gibbons

• Arboreal apes
• tropical rain forests of southeast asia
• 12 species in four (sub-)genera
• subgenera are somewhat more different than humans
  and chimps
• brachiation
• monogamy
• like 3 of mammal species
• 90 of bird species

16
Gibbons and usPrimate Phylogeny
Among the apes, only gibbons and humans have pair
bonding.Also, only gibbons and humans sing
17
Gibbon duetting

• All species of gibbons are known to produce
  elaborate, species-specific and sex-specific
  patterns of vocalisation often referred to as
  "songs" (Haimoff, 1984 Marshall Marshall,
  1976). Songs are loud and complex and are mainly
  uttered at specifically established times of day.
  In most species, mated pairs may
  characteristically combine their songs in a
  relatively rigid pattern to produce coordinated
  duet songs. Several functions have been
  attributed to gibbon songs, most of which
  emphasise a role in territorial advertisement,
  mate attraction and maintenance of pair and
  family bonds (Geissmann, 1999 Geissmann
  Orgeldinger in press Haimoff, 1984 Leighton,
  1987).

18
The female great call

• The most prominent song contribution of female
  gibbons consists of a loud, stereotyped phrase,
  the great call. Depending on species, great calls
  typically comprise between 6-100 notes, have a
  duration of 6-30 s. The shape of individual great
  call notes and the intervals between the notes
  follow a species-specific pattern.
• . A female song bout is usually introduced by a
  variable but simple series of notes termed the
  introductory sequence it is produced only once
  in a song bout. Thereafter, great calls are
  produced with an interval of about 2 min. In the
  intervals, are so-called interlude sequences
  consisting of shorter, more variable phrases
  The typical female song bout hence follows the
  sequential course ABCBCBCBC,

19
Male duet contributions

• As a rule, adult males do not produce great
  calls, but "male short phrases" only. Whereas
  female great calls remain essentially unchanged
  throughout a song bout, males gradually build up
  their phrases, beginning with single, simple
  notes. As less simple notes are introduced, these
  notes are combined to increasingly complex
  phrases, reaching the fully developed form only
  after several minutes of singing
• During duet songs, mated males and females
  combine their song contributions to produce
  complex, but relatively stereotyped vocal
  interactions Both pair partners contribute to an
  introductory sequence at the beginning of the
  song bout (A). Thereafter, interlude sequences
  (B) and great call sequences (C) are produced in
  successive alternation
• During great call sequences the male becomes
  silent and does not resume calling until near or
  shortly after the end of the female's great call,
  when he will produce a coda.

20
Gibbon song samples

• Hylobates Lar
• white-handed gibbon
• Female great call with male coda
• Hylobates Muelleri
• gray gibbon
• Female great call with male coda

21
Hybrid Songs
H. Lar
H. Muelleri x H. Lar
H. Lar x H. Muelleri
H. Muelleri
22
Phylogeny of singing in primates
Singing is rare in mammals. It occurs in members
of 26 species in four primate genera Indri,
Tarsius, Callicebus, Hylobates. These are 11 of
primate species and 4 of primate genera. Since
the four singing genera are widely separated,
they are thought to have evolved singing
independently. In all singing primates, both
males and females sing, and duetting usually if
not always occurs. All singing primates are
monogamous (with the possible exception of
humans). Most bird species sing often bird song
is mostly male duetting bird species are also
usually monogamous.
23
Are humans monogamous?
Are humans monogamous?
In most mammalian species, sexual access is
either determined by rank and results in
polygyny or else two individuals become
attached to one another and then isolate
themselves from other members of their
species In humans what is common is
cooperative, mixed-sex social groups, with
significant male care and provisioning of
offspring, and relatively stable patterns of
reproductive exclusion, mostly in the form of
monogamous relationships. Reproductive pairing
is not found in exactly this pattern in any other
species.
--Terence Deacon, The Symbolic Species
24
Gular sac

• Some gibbons have developed a large gular sac
  apparently involved with breath control and/or
  resonance. Gular sac size and song complexity
  seem to correlate across species.
• Symphalangus syndactylus
• (siamang)
• the siamang duet is probably the most
  complicated opus sung by a land vertebrate other
  than man
• --Marshall and Sugardjito (1986)

25
Zebra Finch(Taeniopygia guttata)

• Small songbird (Australia and Timor)
• Highly social (colonies of 20-1000)
• Pair bonding (with frequent cheating)
• Male display, females choose
• bond marked by clumping and preening
• Males sing, females do not
• part of sexual and territorial displays

26
Typical Zebra Finch song
original
slowed x 4

• Not intrinsically pleasing to most humans
• nasal quality, repetitive rhythm
• Production requires difficult motor control and
  large expenditure of energy
• Female Zebra Finches (and competing males)
  are willing to be impressed

27
Song learningin Zebra Finches and other oscines

• Song patterns are species-specific
• However, exposure to adult patterns is necessary
  for normal sing development
• deafened birds develop highly degraded song
• birds reared without adult male modelsdevelop
  degraded but species-typical songs
• Sensitive/critical period for exposure
• 20-35 days after hatching
• Active song develops later
• 60-90 days after hatching

28
Why learned songs?

• Some sub-oscine species have completely
  programmed song
• deafened or isolated birds sing normally
• Suggested advantages of learned song
• more complex or varied song via cultural rather
  than genetic development
• females prefer constrained novelty
• promotes exogamy in large colonies
• intra-species varients of song, called dialects,
  may serve to segregate populations of the same
  species
• promotes endogamy in microhabitats
• more rapid adaptation of the song to different
  acoustic environments

29
Humpback Whale Songs

• Samples
• Variation and change
• At any one time, all whales sing similar songs
• Over time, songs change rapidly

30
Genetic variation and adaptation

• Genetic variation is ubiquitous
• Is a genetic variant worse, neutral or better?
• often this depends on the environment
• including the attitudes of conspecifics
• In a given environment
• some genetic variants may be selected for
• (i.e. produce more offspring)
• producing genetic adaptation to the
  environment(though much genetic change seems
  selectively neutral)
• The population is (part of) the environment
• so the population adapts genetically to itself
• especially
• in social species
• In mating behavior

31
Cultural variation and adaptation

• Cultural variation is ubiquitous
• Is a cultural variant worse, neutral or better?
• often this depends on the environment
• including the attitudes of conspecifics
• In a given environment
• some cultural variants may be selected for
• (i.e. produce more offspring grow or get
  borrowed)
• producing cultural adaptation to the
  environment(though much cultural change seems
  selectively neutral)
• The population is (part of) the environment
• so the population adapts culturally to itself
• especially
• in social species
• in mating behavior

32
The culture of military tactics

• From Greek taxis order, arrangement
• Two main approaches in the ancient world

33
The two patterns

• Heavy infantry like the Macedonian phalanx
• Associated with city-states in the eastern
  Mediterranean
• Light cavalry like the Mongol hordes
• Associated with pastoral nomads on the Eurasian
  steppes
• Choice in many dimensions
• weapons, armor, tactics, lifestyle

34
Herders vs. farmers

• Foot soldiers
• 70 pounds of arms
• helmet, shield
• spear, sword
• Success based on shock of mass formation
• little training required
• Not very mobile

• Mounted archers
• Light bow, no armor
• Success based on mobility
• lots of practice in riding and shooting
• No good at defending fixed positions

35
Geography of two military cultures
36
Comparison of two failed invasions

• In 514 B.C., the Persian king Darius tried to
  conquer the Scythian nomads (roughly in the area
  of present-day Ukraine). He chased them all over
  their vast domains, and finally had to return
  home in frustration.
• Darius invaded Greece in 490 B.C. He sacked a few
  cities, and was defeated by the Athenian infantry
  (who were outnumbered 3 to 1) at the battle of
  Marathon. The Athenians caught the Persians
  unprepared by running a mile in full panoply,
  which was an unheard-of tactic at the time.

37
The Greek historian Herodotus describes both
invasions, and admires the ability of the
Scythian nomads to win without pitched battles
The Scythians indeed have in one respect, and
that the very most important of all those that
fall under man's control, shown themselves wiser
than any nation upon the face of the earth. Their
customs otherwise are not such as I admire. The
one thing of which I speak is the contrivance
whereby they make it impossible for the enemy who
invades them to escape destruction, while they
themselves are entirely out of his reach, unless
it please them to engage with him. Having neither
cities nor forts, and carrying their dwellings
with them wherever they go accustomed, moreover,
one and all of them, to shoot from horseback and
living not by husbandry but on their cattle,
their waggons the only houses that they possess,
how can they fail of being unconquerable, and
unassailable even?    
38
Summary of the example

• Adaptation of weapons, military tactics
• Asian steppe vs. Mediterranean coast
• Herding vs. farming
• Nomadic bands vs. walled cities
• Continuing cultural variation
• proliferation and copying of what worked best
• result consistent patterns across thousands of
  years and miles
• Process was (entirely?) cultural
• some genetic effects are possible
• 300 generations
• Cultural adaptation to two ecological niches
• fitness depends on the environment
• cultural and geographical

39
Genetics vs. memetics

• Many similaritiesevolution as descent with
  modification
• Differences
• Mechanisms of descent
• sexual reproduction vs.imitation and borrowing
• Mechanisms of innovation
• random mutation/recombination vs. explicit
  problem-solving
• Rate of change

40
How do behaviors and abilities evolve?

• Algorithm development by descent with
  modification
• Some convincing (modeled) examples
• General principles could apply to individual or
  cultural learning as well as genetic learning
• The mapping from genes to behavior is almost
  completely mysterious(but the mapping from genes
  to anatomy is almost as mysterious)

41
ExampleStrategies for the Iterated Prisoners
Dilemma

• The prisoners dilemma paradox
• The iterated prisoners dilemma
• Proposed in 1984 by Robert Axelrod
• The IPD tournaments
• Genetic algorithms
• Applications of GA to the IPD

42
The prisoners dilemma paradox

• Origin situation of captured thieves
• if everybody keeps silent, all go free
• if one confesses
• (s)he gets a reward
• everyone else gets a heavy sentence
• if everyone confesses
• everyone gets a moderate sentence
• If you analyze the options objectively, your
  best bet is to confess. But if everyone
  confesses, everyone is worse off than if everyone
  kept silent.
• Generically total cooperation is better than
  total non-cooperation but any individual can
  then better his or her situation by defecting.

43
PD payoff matrix(payoff to me)
Temptation gtgt Reward gtgt Punishment gtgt Suckers
payoff
Also (Temptation Sucker)/2 lt Reward
44
Consider the options

• If you defect
• if I cooperate I pay 100
• if I defect I pay 10
• so my best bet is to defect
• If you cooperate
• if I cooperate I get 300
• if I defect I get 500
• so my best bet is to defect

45
PD without money or copsthe furry critters
dilemma
46
Conclusion nice guys finish last

• PD arguments were used to prove that
  cooperation could never be an evolutionarily
  stable strategy, except perhaps among kin
• Every man for himself, and the devil take the
  hindmost
• A depressing conclusion in the context of the
  cold war, where nuclear standoff looks very much
  like a PD situation.

47
Axelrods innovation(1984)

• Treat PD as a game with repeating turns
• Endless, or at least players dont know when the
  end will come
• Add up the scores across turns
• Play different strategies against one another
• Human game-playing
• Better, let the computer do it

48
Payoff matrix for Axelrods game
49
First try

• Axelrod advertised for strategies
• 14 were submitted, some very complicated
• Axelrod added one Random
• Run a tournament every strategy plays against
  every other strategy 200 times
• The winner
• Tit for tat (submitted by Anatol Rapoport)
• Cooperate with strangers, and otherwise do
  whatever the opponent did last time around
• If we define a nice strategy as one that is
  never the first to defect, then the 8 top scoring
  strategies (out of 15) were nice.
• Forgiving strategies do better than those that
  bear grudges
• in fact, tit for two tats would have won if it
  had been entered

50
Second try

• Analysis of first tournament was published
• Second tournament was opened to any new entrants
• 62 entrants this time
• number of rounds was left open
• Result tit for tat wins again
• including against tit for two tats

51
More results

• Many other analyses and competitions
• Two attempts at evolutionary simulations
• (1) Evolutionary competition among fixed set of
  63 strategies
• tit for tat won 5 out of 6 rounds
• A similar nice, forgiving strategy won the 6th
• However, no such strategy is evolutionarily
  stable, in the sense that a uniform population
  can always be successfully invaded by an
  alternative.
• (2) Genetic algorithm to evolve new strategies
  and let them compete

52
Evolving PD strategies

• Strategies as pseudochromosomes
• 4 possible outcomes at each stage of the game
• 4 x 4 x 4 64 possible 3-move histories
• To determine how to act in each of these 64 cases
  requires 64 specification of C (cooperate) or
  D (defect)
• Thus a PD gene is a string of 64 Cs or Ds
• Add 6 more to cover the first 3 moves
• Total of 70 letters make up a pseudochromosome

53
Mutations and mating

• Mutation just change one of the 70 letters from
  C to D or from D to C, with some small
  probability
• Mating combine two genotypes by selecting a
  random crossover point
• crossover point of 9 combines 1-9 from one parent
  with 10-70 from the other, and vice versa

54
Natural selection

• Run a mini-tournament and score each genotype
• Mate genotypes (with random mutations) to produce
  offspring in proportion to their score on the
  previous round of the tournament

55
Results overall population fitness improves
56
Gene pool analysis

• Five alleles evolved in the vast majority of
  individuals
• Dont rock the boat if RRR then C
• Be provocable if RRS then D
• Accept apologies if TSR then C
• Forget if SRR then C
• Accept a rut if PPP then D
• Most of the resulting individuals beat
  tit-for-tat

57
Emergent propertiesof group behavior

• Descriptions at different levels
• temperature, sound vs. molecular motions
• cell vs. macromolecules
• organism vs. cell
• ant colony vs. individual ants
• marketplace vs. individual merchants
• Some key properties only emerge in group
  interactions

58
Why this matters

• Fitness is often determined by emergent
  properties
• Fitness in multicellular organisms cant be
  determined by looking only at individual cells
• Fitness in social organisms cant be determined
  by looking only at individuals

59
Ant path selection
60
Ant problem solving
61
Termite mound
62
How social insect behavior evolves

• individual properties are genetically controlled
• pheremone chemistry
• when to emit which pheremones
• effects of sensing pheremones
• the Termite Machine is like a Turing
  Machinethat reads and writes smells rather than
  symbols
• intelligent group, stupid individuals
• plans and decisions exist only at the group level
• dispositions of individuals are like elements of
  a circuit or statements in a program
• evolutionary environment is (mainly) the group
• like the evolutionary situation of multicelled
  organisms

63
Adam Smiths invisible hand
A merchant generally, indeed, neither intends
to promote the public interest, nor knows how
much he is promoting it.   He intends only his
own gain, and he is in this, as in many other
cases, led by an invisible hand to promote an end
which was no part of his intention. By pursuing
his own interest he frequently promotes that of
the society more effectually than when he really
intends to promote it. Wealth of Nations,
Book IV