Evolutionary Psychology Quiz

Hormones and Behavior

• Eating behavior is influenced by hormones.
• Hunger is caused by hormones leptin and ghrelin.
• Leptin, released from fat cells, signals to the hypothalamus to reduce hunger. Higher fat storage = higher leptin, resulting in lower hunger.
• Low leptin levels trigger ghrelin release from the stomach, increasing hunger.
• These hormones are proximate factors affecting animal behavior.

Hormonal Control of Behavior

• Hormones play a key role in developing brain and gonadal structures, directly or indirectly impacting behavior.
• Hormones trigger changes in neural networks, reacting to stimuli like daylight or social cues.
• Reproduction is often timed by hormones when environmental conditions are most favorable.

Internal Clocks and Biological Rhythms

• Biological rhythms persist independently of the environment.
  • Short rhythms (e.g., heartbeat, breathing)
  • Circadian rhythms (24 hours, e.g., rest/foraging)
  • Circalunar rhythms (monthly, e.g., menstrual cycle)
  • Circannual rhythms (yearly, e.g., migration, reproduction)
• Internal clocks are critical for navigation and timing of ecological activities.
• Two hypotheses explain rhythms:
  • Environment-independent: rhythms persist regardless of environment.
  • Environment-dependent: rhythms are adjustable to environmental changes.

How Internal Clocks Work

• Researchers use invasive methods, such as brain lesioning, to study the function of internal clocks.
• Studies are also performed on brain-damaged individuals and insects.
• Removal of optic nerve influences but does not fully eliminate rhythms. Removal of the optic lobe disrupts rhythms. Melatonin production is necessary for light/dark reception.
• Certain animals, like naked mole-rats, which live underground, show little to no circadian rhythm due to lack of a light/dark cycle.

Hormones: The Chemical Messengers

• Hormones are found in all multicellular organisms.
• They are chemical messengers between cells.
• Many organs/tissues produce hormones.
• Mammals have approximately 50 major hormones.
• Hormones are derived from amines, peptides, proteins, and lipids.
• Hormones can function as neurotransmitters.

Functions of Hormones

• Endocrine action: hormones secreted into the bloodstream.
• Paracrine action: hormones diffuse across cells.
• Lipid hormones can act both ways.
• Hormones affect CNS; hypothalamus produces hormones.

Importance of Clocks and Hormones

• Hormones and internal clocks influence fat deposition, migration, and hibernation. Changing day lengths lead to circadian rhythm changes, affecting feeding and behavior (e.g., increased body fat storage).
• Hormone levels change during reproduction (e.g., progesterone during pregnancy, prolactin for parental care).
• Reproductive behaviors and sexual motivation are influenced by the balance of testosterone, estrogen, and progesterone in mammals and birds.
• Estrogen in female Rhesus monkeys peaks during estrus, correlating with mating. Artificially increasing estrogen levels in female Rhesus monkeys increases mating behavior.

Sex Peptides and Sexual Receptivity

• In flies, sex peptide, transferred during mating, increases egg laying and decreases female receptivity.
• Sex peptide targets brain areas similar to the human hypothalamus. This process is widespread.

Effects of Copulation

• Copulation leads to rapid changes in female receptivity (e.g., in green anoles).
• Immediate post-copulatory unreceptivity is driven by prostaglandin rise in green anoles.

Testosterone

• Testosterone promotes sperm production, sexual behavior, suppresses the immune system, and influences aggression in many species.
• Testosterone is produced in the testes (males) in response to pituitary glycoprotein hormones (from the brain).
• Testosterone is linked to secondary sexual characteristics (e.g., rooster wattles).
• In guinea pigs, testosterone directly influences sex drive.

Testosterone and Aggression

• In humans, higher endogenous testosterone levels correlate with increased aggression/dominance.
• Testosterone levels rise in anticipation and after aggressive incidents.
• Testosterone and aggression is linked according to The Challenge Hypothesis.

The Challenge Hypothesis

• Conducted field experiments within natural environments to test the relationship of testosterone and aggression.
• Demonstrated testosterone response to social challenges.

Testosterone & Aggression in Females

• Females produce testosterone, and it exerts similar effects.
• Increased female competition can lead to raised testosterone levels.

Testosterone and Parental Care

• Testosterone levels potentially affect human paternal involvement.
• Lower testosterone levels are found in married fathers compared to unmarried non-fathers. Fathers with higher care have lower testosterone. Polygnous men with high mating levels often have high testosterone.

Costs of Testosterone

• Castrated males tend to live longer.
• Different male morphs (e.g. orange-throated, yellow-sneaker, blue-throated) have varying testosterone levels and survival rates. High testosterone is linked to increased activity and territory defense but also decreased survival.

Aggression

• Many social species exhibit dominance hierarchies.
• Human competition for status can be linked to achievement, and other forms of performance.
• Facial features (e.g., jaw shape) can correlate with perceived social dominance.

Parental Behavior

• Parental investment varies across species. Any action increasing offspring fitness is considered parental care.
• Parental investment is a trade-off—increased investment in current offspring reduces future reproductive potential.

Who Should Care?

• Usually, female mammals invest more than males in raising offspring. Females also have the higher biological investment into producing the egg.
• Exceptions exist in certain species (e.g., seahorses). Males may play the primary role in care.

Parental Investment

• Variation in male parental investment exists. (e.g., peafowl, mute swans, jacana)
• Operational sex ratio (OSR) influences male and female roles in parental care. Males often compete for females or females are selective in choosing mates.

Parental Conflict

• Conflict over parental care occurs in species where both sexes can care.
• Operational sex ratio substantially influences conflict over parental care.

Avoiding Misdirected Care

• Avoiding caring for non-genetic offspring is a selective pressure across many social species.

Parental Cost Cutting & Brood Parasitism

• Brood parasitism occurs when one individual lays eggs into another's nest.
• Cuckoos provide examples of adaptations for brood parasitism like egg mimicry.

Adoption Behaviors

• Adoption occurs naturally in some species.
• Costs & benefits are evaluated for adoption behaviour.

Male Territory Take-Overs

• Males sometimes temporarily care for the eggs of rival males evicted from their territories.

Biparental Care

• Biparental care increases when both adults benefit from the care, like in birds and humans. Uncertainty over paternity and less selective care.

The Sociology Debate

• Evolutionary and sociological factors can shape behavior.
• Evolutionary explanations must consider broader factors. Child abuse, murder, and rape have been explored evolutionarily, but that is not the only view, and other factors must be considered.