Exam 2 Review

What is sexual selection?

Adaptations that increase an individuals fitness via REPRODUCTIVE SUCCESS

Conditions for sexual selection: Different reproductive success among members of the same sex = non-random mating (involve gametes, reproductive investment, parental investment)

What is intersexual selection?

Selection for traits that improves one’s success in attracting members of another sex

What is intrasexual selection?

Selection for traits that improve one’s success in competition with members of one’s own success

What is sexual dimorphism?

(aka polymorphism); Differences among the sexes in various traits

Such as:

Body size

Canine size

Scent marking behavior

Vocal behavior

Visual ornamentation

How do male and female reproductive strategies typically differ due to differences in reproductive potential/variance?

Male reproductive strategies often focus on maximizing mating opportunities, as males usually have a higher reproductive potential and variance. This can lead to behaviors such as competing for females and seeking multiple mates. In contrast, female reproductive strategies are often more selective due to lower reproductive potential and variance, focusing on quality over quantity in mate selection, as females typically invest more in offspring. This fundamental difference drives distinct mating behaviors and social dynamics in many species.

Define reproductive potential

Possible output of offspring by one sex

What is reproductive variance?

Variation in reproductive success within a sex

What are the characteristics of a limiting sex?

Low reproductive potential; low variance (i.e. women compared to men)

Should be more discriminating over partners

Should show more intrasexual competition over mating opportunities

What does the SRY gene do?

The SRY gene, located on the Y chromosome, encodes the Testis Determining Factor protein, which is produced around 6-8 weeks and induces male differentiation.

What happens to XY individuals who lack a functioning SRY gene?

XY individuals who lack a functioning SRY gene often follow typical female development.

What is the effect of XX individuals with a functioning SRY gene?

XX individuals with a functioning SRY gene typically follow male development.

What are some important genes involved in sex differentiation besides SRY?

Other important genetic contenders include SOX9, WT1, SF-1, DAX-1, and DSS.

What determines whether individuals develop as male or female?

Everyone has genes that can develop into either male or female; it is the expression of these genes that varies.

When do hormones start to influence external genitalia?

Hormones begin to shape external genitalia starting around 13 weeks.

What role do testosterone and androgens play in sex differentiation?

The presence of testosterone and other androgens leads to male differentiation.

What occurs in the absence of testosterone regarding sex differentiation?

In the absence of testosterone, individuals typically develop female characteristics.

What is Nature vs Nurture?

Nature vs Nurture is a longstanding debate in psychology and sociology that examines the relative influence of genetics (nature) and environment (nurture) on human behavior and development. Nature refers to the biological and genetic predispositions that individuals inherit from their parents, including traits such as intelligence, personality, and physical characteristics. Nurture encompasses the environmental factors that shape an individual's experiences, including upbringing, culture, education, and life experiences. The interaction between these two elements is complex, with researchers exploring how much of behavior can be attributed to genetics versus how much is influenced by an individual's environment.

What is play?

Seemingly “non serious” variants of functional behavior

Playful behaviors resemble serious behaviors but participants are typically concerned with the behaviors themselves (i.e. the means) rather than the function (i.e. the goal) of the behavior

Playful behaviors are also typically more exaggerated than their functional counterparts (i.e. play fighting)

What are the costs of play?

Involves a lot of energy

Takes up time

Social play can lead to conflict

Rough and tumble can result in injuries

Define the Surplus Energy Hypothesis

Only play when an organism has enough energy and time to dedicate to play

What are some benefits to play?

Recall surplus energy hypothesis

Motor Training Hypothesis: play allows individuals to practice and perfect motor skills needed to catch prey, avoid predators, fight competitors, attract a mate, and protect infants

Social relationship hypothesis: Play allows individuals to learn behavioral characteristics of other individuals and how to negotiate relationships

How/Why does play differ amongst sexes?

Differences in play might arise depending on the relative importance of motor skills and social relationships for males vs females

We treat kids differently based on how we perceive their gender

How kids play affects brain development, motor skill development, and social development

These developmental differences can have long lasting effects on behavior

What are the play behavior differences between male and female macaques?

Male macaques often engage in rough-and-tumble play, which is linked to the development of aggression and social dominance. In contrast, female macaques generally participate in a wider variety of play behaviors that incorporate social interaction and nurturing activities.(hold stick; more attentive to foraging)

In matrilineal societies, how do female infants/juveniles compare to males in grooming behavior?

In matrilineal societies, female infants and juveniles spend more time grooming than males, focusing on grooming maternal kin, likely to foster social bonds.

Why are young female primates often more attentive to their mothers when fishing?

Young females are more attentive to their mothers when fishing, likely due to learning and social bonding.

How do young females compare to males in terms of learning fishing efficiency?

Young females learn faster and are more efficient than males when it comes to fishing.

What fishing style do female primates typically exhibit?

Females show a fishing style similar to their mothers, especially in fishing for termites, emphasizing female nutrition's importance for reproduction.

What behavior is observed in adolescent female primates regarding infants?

Adolescent female primates often steal infants and show eagerness to interact with them and practice care.

How common is infant care practice among adolescent male primates?

The eagerness to interact with infants and practice care is less commonly observed among adolescent male primates.

What influence does sexual dimorphism have on growth patterns in primates?

Sexual dimorphism varies depending on mating systems; for example, Mandrils have larger males that grow faster during adolescence compared to females, while Marmosets show similar growth patterns in males and females.

What mating systems are observed in primates?

Monogamy - one female mates with one male; parental investment; less dimorphism (i.e. gibbons)

Polyandry - one female mates with multiple males'; cooperative breeding - twins; rare (i.e. tamarins)

Polygyny - One male with multiple females; can occur in different social systems (i.e. gorillas); referred to as harems; implied male ownership and no female choice (biased research views) Hamadryas: males are aggressive towards females; females are unrelated; when male dies or is defeated, females disperse. Geladas: males are accepted by females; females are related; when male dies or is defeated, females remain together

Polygynandry - Multiple females mate with multiple males (most common) (i.e. orangutans) The more females in a group, the less likely one male can control mating with all of them (i.e. less likely males can keep other males out of the group)

What is dispersal?

Emigrating from natal group and immigrating into a different social group

Primates disperse around the time of reproductive maturity

• Why? to prevent inbreeding

Dispersal patterns: one sex or both sexes might disperse; male is most common in primates

What is the socioecological model?

The socioecological model attempts to explain primate sociality using ecology

• Ecology: the relationship between organisms and their environment

What resources typically matter the most for females and males?

Predation affects female distribution, which affects male distribution

Predation pressure favors female grouping

Food distribution affects female competitive regimes

Female distribution in turn affects male distribution

Food distribution affects the types of social relationships within groups

How do mating systems relate to sexual dimorphism?

Patterns are shaped by type and intensity

There is the least dimorphism in pair living species

• Polygyny M»F

• Polygynandry M>F

• Monogamy M=F

• Polyandry M<=F

What is Dominance Rank?

Dominance reflects an asymmetry in social power between individuals

• Dominant vs Subordinate

Dominance is ranked or measured based on:

• Who repeatedly wins fights

• Based on frequency and on direction of agonistic displays (threats vs submissive behavior)

• Based on approach - retreat interactions

Why is dominance rank important?

In primates that fight over dominance, dominance rank strongly correlates with reproductive success

Think Priority Access Model: highest ranking male mates the most; but when too many females are ovulating, he cannot prevent other males from mating with all of them, so second rank male gets to mate

High ranking female gets priority access to food

Higher ranking baboon mothers have offspring with better survival

Higher ranking females have daughters who mature faster

Have biases of researchers shaped our scientific viewpoints?

OFC!
Polygyny - was implied male ownership/ no female choice (biased views)

Traditional viewpoint: male dominance hierarchies are the backbone of primate societies

• This was partially shaped by biased views

Updated: Males and females both have dominance hierarchies in many species

• Kin networks + rank are typically the backbone of primate societies

What is mating?

Copulation: sexual behavior in which a male introduces sperm into the female’s reproductive tract

Copulation or mating is typically a reproductive behavior

Non-conceptive and conceptive mating

typically dorsal ventral (same direction) some ventral ventral (humans or gorillas)

What is sexual behavior?

Involves hand to genital, mouth to genital, or genital to genital contact

Sexual behaviors can be non-reproductive

• perhaps the distinction lies in that mating involves conception as the goal whereas sexual behaviors that may not be implicit

Is mating decoupled from fertile periods in primates or other mammals?

In most primates (except some strepsirrhines) mating ability is decoupled from fertile window and hormonal control:

• Juvenile primates mate

• Mating outside the ovulatory window

• Hormones are linked to sexual motivation

• Hormones, social relationships, environment, context, and cognition all matter for primates

Is mating always cooperative for primates?

NO: Uncooperative mating behavior stems from sexual conflict (different interests for individuals involved)

Coercion and harassment examples; rare among primates but common for orangutans

Adoption - male guards female juvenile until maturation

For many primates species, if a female does not want to mate she can just sit down

What are some examples of proactive mating behavior?

Proactive is acting in a way that explicitly shows interest and attempts to gain the attention of a potential mating partner; an active participant

Female sexual swellings

• Chimps differentially advertise these swellings to others

Male coloration and size

Chimps are often observed adorning themselves with leaves, fruits, vines, etc.

Signal quality and or interest in mating partners

How do individuals attract each other?

Proactively presenting sexual swellings • Males grooming and following females around (consortships) • Some more subtle behaviors like eye contact • “Flirting” behaviors

Females present their sexual swellings to males they are interested in • Signaling they want to mate • Sometimes they do this repeatedly (and are really annoying) if the males do not pay attention

Brighter mandrills are more successful… but this does not mean female are choosing them

Is there evidence that sexual signals matter?

Yes. For example, female mandrills approach more brightly colored males, and vervet females respond to male coloration. However, it's hard to separate signal preference from dominance effects.

Do partners choose based on signals?

In many species, yes-signals like color, behavior, and swelling are used to attract mates or indicate receptivity.

What is same-sex sociosexual behavior (SSB)?

Sexual behavior between individuals of the same sex, including genital contact, mounting, etc. It is a behavior, not an identity

How does SSB differ from "homosexuality" or queer identities?

SSB is a behavior. Queer identities involve enduring romantic/emotional attraction and are human-specific social constructs.

Is SSB common in the animal kingdom?

Yes, it's reported in 1500+ species, especially primates.

What were the historical evolutionary views of SSB?

Seen as maladaptive due to lack of reproduction-termed a 'Darwinian paradox.'

How have hypotheses for SSB changed?

Shifted from seeing it as a pathology to viewing it as adaptive-facilitating social bonds, reducing tension, or forming alliances

What are best practices for SSB research?

Use diverse research teams, reflect on biases and impacts, and consult affected communities.

What are the main phases of the female reproductive cycle?

Menstruation, ovulation, fertilization (if it occurs), and repeat cycle if no pregnancy.

What are some costs of female reproduction?

Egg production, gestation, lactation (most costly), and long-term infant care.

What is the most energetically costly phase?

Lactation-due to demands on energy, nutrient production, and infant growth.

When should a female move on to her next reproductive cycle?

When the costs of continued investment outweigh the benefits; differs for mother vs. offspring.

How to deal with reproductive costs?

Strategies include delayed maturation, good nutrition, shorter reproductive span, and spacing births.

What are ways to increase access to food?

High social rank, alliances, and seasonal timing of reproduction.

How to reduce competition?

Through reproductive suppression (e.g., subordinate females don't cycle), aggression, and harassment to reduce rival conception chances.

What is female choice and when does it occur?

Discriminating among mates; expected when females are the limiting sex due to high investment in reproduction

What do females choose males based on?

Direct benefits (e.g., protection, food, care) and indirect benefits (e.g., good genes, attractive offspring).

Are female choice and promiscuous mating mutually exclusive?

No. Females may mate with multiple males and still exercise choice.

What are exaggerated sexual swellings?

Large changes in perineal skin that signal receptivity; found in some African and Asian monkeys and apes.

Who has exaggerated sexual swellings?

Species with multi-male mating systems, like baboons and chimps.

In what ways do swellings vary?

Within cycles, between cycles, and between individuals in size, color, and timing.

Hypotheses for exaggerated sexual swellings?

Graded-Signal Hypothesis: Swellings both confuse paternity by allowing multiple matings and concentrate paternity in high-quality males through peak swelling at ovulation.

Cycle Differentiation Hypothesis: Swelling size increases across cycles; helps males gauge conception likelihood and allocate mating effort.

Female Quality Hypothesis: Swelling size honestly signals overall female quality (e.g., health, parity), though evidence is mixed.

Parental Care Hypothesis: Males use swellings to assess likelihood of paternity and adjust level of care accordingly.