From Last Class

Ethology

• Animal behaviours in natural environment

Species-specific behaviours

Homologies

• Detail and mechanisms

Analogies

• Similar function

Non-verbal expressions

• Ritualization, antithesis, autonomic responses

Emotional expression

Sociobiology

Social systems in animals

• Why are they adaptive?

Behaviours interacting with other behaviours

• Mating, agression, cooperation

Compare and contrast species

• Environmental factors?

Dr. E.O. Wilson

Mating Patterns

Polygyny

• One male, multiple females

Polyandry

• One female, multiple males

Monogamy

• One female, one male

Polygynandry

• Multiple males and females in social group

Who gets to mate?

Parental investment?

Polygyny

Fairly common in mammals

Females have high parental investment

• Gestation
• Lactation
• Rearing

Males have low parental investment

• Mating

Not all males get to mate

• Aggression

Polyandry

Very uncommon in mammals

• Naked mole rats

Often in non-mammalian species

• Egg layers

Females have low parental investment

• Lay eggs

Males have high parental investment

• Often, one chance to mate
• Sometimes carry/tend the eggs

Monogamy

Equal parental investment

• Takes both parents to raise offspring

Little sexual dimorphism

Seen in:

• 90% birds
• 3% mammals
• Feeding

Cheaters

• Males: low additiona investment
• Females: increased genetic diversity of offspring

Polygynadry

Rare

Bonobo chimpanzees and common chimpanzees

• Colony
• Promiscuity

Advantages?

• Males do not know which offspring are theirs
  • Protect all offspring
  • Protect all females
• Males do not fight over females
  • Sex used to reduce social tensions

Consortship

Incest

Mating with a close relative

Evolutionary disadvantage

• Recessive disorders

Incest avoidance techniques

• Kinship recognition
• Migration

Chimpanzees

• Show both avoidance techniques
  • Females tend to move to a new colony
  • Strange female effect

Aggression

Fighting and threats of fighting

Fighting to mate

• Polygyny
• Males compete for females

Territoriality

• Feeding ranges
• Territorial signaling
  • Helps avoid fighting

Dominance within a colony

• Submissive signals
• Dominance hierarchies

Helping

Cooperation

• Individual helps another while helping itself
  • Hunting
  • Protection
• Selfish
  • Obtains resources that can not be gotten alone
  • Increases chance of survival

Altruism

• Kin selection theory
  • Help close relatives
  • Increases similar genes in population
  • e.g., social insects, wolf "aunts"
• Reciprocity theory
  • Long-term cooperation
  • Memory

Sociobiology and Humans

Consider:

• Handsome stranger comes to town
• Fences around backyards
• Cheating in a relationship
• Lending class notes

Can sociobiology be applied to humans?

Deterministic Fallacy

• Genes play a role in determining behaviour: TRUE
• Genes determine behaviour regardless of environment: FALSE

Naturalistic Fallacy

• Natural selection and morality

Analogies

• A good way to generate a hypothesis
• The hypothesis must be tested through detailed study!

Some Hypotheses About Humans

Communal living

Nepotism

Monogamy and Polygyny

Men are more violent than women

Avoidance of incest

Chapter 4 In Short Form

Evolution is about adaptation

Levels of adaptation

Ultimate and proximal causes of behaviour

Genetic drift

Ethology

Species specific behaviour

Homologies and analogies

Non-verbal expressions

Emotional expressions

Sociobiology

Mating patterns and parental investment

Aggression

Helping

Sociobiology and humans

For Your Consideration...

In species in which males fight over the right to mate with females, natural selection tends to make the males larger than the females. What limits the eventual size of the males? In other words, what selection pressures balance selection for increased size? Hint: think about energy requirements.

Wolves have evolved a complex communication system in their howls. What use might this serve?

What social behaviours can help prevent the spread of dangerous recessive genes in a population? If an animal is only considered to be "successfully" if it passes its genes on to the next generation, how did altruism every evolve?