Biological Basis of Human Behavior

ANTH 1005 Flashcard Set

Jean-Baptiste Lamarck

• past idea that selection happened over the lifetime

• Ex. giraffe neck gets longer as it uses it more during lifetime

Charles Darwin

Developed the theory of natural selection. He proposed that organisms better adapted to their environment are more likely to survive and reproduce, leading to the gradual evolution of species over time.

Phylogenetics

Study of the evolutionary relationships among organisms. Comparative method through taxonomy 

Negative assortative mating

choosing a partner that is phenotypically different

Positive assortative mating

choosing a partner that is phenotypically similar but can lead to inbreeding depression

Epigenetics

study of how changes (inside and outside of the body) influence gene expression. Nature vs Nurture.

Minnesota Twin Study and Adoption Studies

both investigate the impact of outcomes of people from biological versus environmental lenses.

Darwinian Evolution Concepts

Phenotypic variation, variation heritable, differential fitness.

Behavioral Ecology

determine how  individual behavior is shaped by the environment. Highlights individual variation

Behavioral Ecology Criticisms

Focuses on current fitnss value and evolution has a longer lens with respect to adaptation.

Evolutionary Psychology

Emphasis that the underlying neurological structures are under selection. As eather became cooler and drier and food became sparse, changed human brain to be under selection to problem solve.

Criticisms of Evolutionary Psychology

Determinism- every change because of that one event and not tohr factors and assumption nothing happened the past 1.5 million years.

Give an example of Gene-Culture Evolution

lactose intolerance or those living in higher altitudes have higher levels of hemoglobin.

Characteristics of Primates

• Forward-facing eyes

• Stereoscopic vision

• Reduced olfaction

• Several types of teeth

• Nails instead of claws

• Grasping hands and feet

• relatively long lifespans

• relatively large brains to body size ratio

• reduced reliance on olfaction

• long development and lifespan

What are the 2 Suborders of Primates

1. Prosmismii (prosimians) or Strepsirrhini

2. Haplorhini or Anthropoidea (depending upon the placement of tarsiers)

Strepsirrhines 3 Features

• 1) dental tooth comb, associated with reduced upper incisors; 

• 2) flaring talus (ankle bone  that flares)

• 3) grooming claw on the second digit of feet

older suborder of primate

Anthropoid Suborder (AKA Haplorhines)

• Nocturnal

• Shift to being habitually diurnal is a distinguishing feature of anthropoids – associated with greater emphasis on visual versus olfaction

• Forward facing eyes and well-developed stereoscopic vision

Bipedalism Advantages

• Efficient terrestrial locomotion

• Free Hands to carry and make tools

• Efficient Foraging

• See distances

• Keep Cool

Bipedalism Disadvantages

• Slower

• Less Stable

• Limited climbing ability

• Back problems

• Obstetrical dilemma

What is the Obstetrical dilemma

Because of bipedalism pelvic size and shape is constrained, thus newborns are only able to grow to certain size/have less brain development before delivery. Babies are very altrustic

Homo Habilis (~2.3-1.4 mya) 

• larger brain and flatter face than australopiths

• small australopith-like body

Homo Erectus  (~1.89 mya - 143,000 ya) 

• shorter arms and longer legs

• Modern feet

• Smaller teeth

• Larger brain

•  First to leave Africa

Extra Credit: Why does Dr. Murray likes Neanderthals?

Because of baby “daycare” footprints were found and a beaded baby-carrying tool was used. Inherited baby care!

How many Bones are Estimated to be around?

1,000-10,000 bones

Monogamous

one male, one female

Polyandry

one female, multiple males

Polygyny

one male, multiple females

Socio-Ecology

The  study of how social structure and organization are influenced by organisms’

environment

Anisogamy

a form of sexual reproduction involving the fusion of two gametes (reproductive cells) that differ in size, structure, and/or motility

Reproductive Potential for Males vs. Females

• Females potential limited by access to food

• Males potential limited by access to mates

Sex-Biased Dispersal

One or both sexes disperse (emigrate) at sexual maturity to avoid inbreeding. Inbreeding avoidance hypothesis

Inbreeding avoidance hypothesis

species evolve behavioral, biological, or social mechanisms to prevent mating between close relatives and reduce the fitness

Male Reproductive Skew

Males have higher reproductive potential. More male competition to either have a monopoly over females to have a harem or spread partners more. Apha Males can get 30-40% of women/offspring.

Sexual Dimorphism

condition where males and females of the same species have different physical characteristics or appearance beyond their reproductive organs. Ex. male peacock colors

Give morphological evidence that humans have long history pair bonding?

• Not as much sexual dimorphism(ex. male height, etc)

• No canines

• Human males have lower sperm quality in comparison to other mammals

Test Question: if you see females clumped in an area what assumptions could you conclude?

Think!

Distinctive features of the evolved human production system that have direct implications for social organization

• Skill-Based

• Sex-Based Complementarity In Skill Acquisition

• Gains From Cooperation Promote Linkeages

• Non-Defensible Resources (Economically Defensible)

Intra-Sexual Selection

One sex competes for access to another (usually males). Favors traits that enhance competitive ability

Sexual Dimorphism

males and females differ phenotypically in many species and difference reflects intensity of intra sexual competition.

Inter-Sexual Selection

Between males and females. Differences in attractiveness to the opposite sex. Usually non-random mate choice by females

Evolution of Elaborate Displays

Although some elaborate displays may have evolved for use in contests between males, some have certainly evolved as a result of selection by females for genetic benefits. ex. female fruit flies mate with male if provides large nuptial gift.

Good Genes Hypothesis

elaborated male traits may be indicators of heritable genetic quality. (ex. fitness). For example Males may have a heritable trait that reduces viability, but males with good genes can survive the handicap

Sexy Sons Hypothesis

Process at point where the ONLY benefit to female choice is that her sons inherit the most attractive trait. even though trait itself can become a fitness burdern

Fisherian Runaway Selection

exaggerated and costly male physical traits—like a peacock's tail—can evolve through persistent female choice

Figure is an Honest Signal of fertility

• For women 0.7 Waist to Hip ratio “desired”

• For men T shape higher shoulder to hip ratio have more partners

Non-Human Species Preferences: Symmetry

Most costly traits may theoretically be the basis of female preference for symmetry

Pheromones

chemical signals that lead to a behavioral response. have been linked to sexual attraction in both men and women.

Cuckholdry

male invests in offspring from another male

What Women Gain Through STM

• Resource Hypothesis: Paternity confusion - Protection -Status enhancement - Mate Switching if Current Partner Cannot Provide

• Genetic Benefits Hypothesis: Sexy son, Genetic Diversity, Good genes

Life History

age-specific reproduction and mortality rates, and the entire sequence of changes through which an organism passes in its development from conception to death 

Life History Variables

• Gestation Length

• Age at Weaning

• Age at First Reproduction

• Inter-birth interval

• Litter size

• Maximum lifespan

Extrinsic mortality

risk of death that is not dependent on an organism's behavior

• If mortality is not an issue, more investment in offspring 

Intrinsic mortality

risk of death associated with how an organism allocates resources towards somatic and reproductive effort.

• If mortality is an issue, not as much investment in offspring, so the goal is to reproduce as much as possible
  
  

Primates Life History

• Long gestation lengths

• Long developmental periods & late ages at maturity

• Low reproductive rates (i.e., they reproduce slowly)

• Long lifespans

Stages of Life History

Gestation, Infancy, Juvenescence, Adolescence, Adulthood

What Stages of Life History is Unique to Humans

Childhood, Adolescence, Menopause

Human Life History compared to Great Apes

• Longer lives

• Late age of sexual maturation

• Short infancy

• Short inter-birth intervals

• Large adult brains

Parental Investment

 Any form of parental behavior that is likely to increase the survival and fitness of young AND decreases the parent’s ability to invest in future reproduction

Parental Investment Theory

Parents should invest in offspring whenever the benefit to THEMSELVES is greater than the cost to THEMSELVES

Parental Care Costs

Reduced ability to invest in future offspring (missed mating opportunities, time to raise). Reduced survival

Operational Sex Ratio

Number of males to actual receptive females

Benefits to Paternal Care

• Increased infant survival

• Heavier infants

• Faster infant development

• Shorter inter-birth intervals for the mother 

Human life histories have four distinctive characteristics:

• Long lifespan

• Extended period of juvenile dependence

• Support by post-reproductive individuals

• Male support of reproduction by provisioning of females and offspring

Challenges to Parental Investment Theory 

1) Men in some foraging societies contribute less than women 

2) Hunting provides such unpredictable returns - poor strategy for provisioning children

3) Foods men acquire (e.g., meat, fish, and honey) tend to be shared widely outside the household

What are Hormones?

Chemical messengers that target specific cells.

2 types of Hormones

• Steroidal hormones (e.g., glucocorticoids, androgens) act directly on a cell

• Protein-based hormones (e.g., vasopressin, oxytocin, insulin).

Behavioral Endocrinology

study of how hormones influence behavior

Peptide Hormones

prolactin, vasopressin/oxytocin

Steriod Hormones

Testosterone, Glucocorticoids

Challenge Hypothesis

Testosterone will increase to increase mating opportunities but testosterone is also costly.

Example of Challenge Hypothesis

dark-eyed junco males provision less when testosterone is experimentally increased. Instead their mating songs increase.

Extra Credit: What is Dr. Murray’s Dog name?

Smooch

Extra Credit: Dr. Murray Memory with Mawmaw

Mawmaw gave Dr.Murray white wonder  bread and mellow yellow  while watching Guiding Light

Extreme Sibiling Rivalry

Obligate siblicide in Brown Bobby

The Grandmother Hypotheses

evolutionary theory suggesting that human females live long past their reproductive years because post-menopausal grandmothers help feed, protect, and raise grandchildren, which increases the survival of their shared genes

Extra credit: why paternal grandmothers may have less connection with offspring

Because with paternal grandmothers, there is more likelihood of the grandchild maybe not biologically their’s so decreased investment. Also since males have higher reproductive potential could possibly have more offspring with multiple mothers than a single mother would produce.

Paternal vs Maternal Grandmother impact on survival

• Paternal: Associated with an increase in grand-offspring survival in 9 out of 17 studies

• Associated with an increase in grand-offspring survival in 9 out of 13 studies

Types of Alloparental Care

• Provisioning and nursing

• Carrying

• Huddling or communal nesting

• Babysitting

• Protection from predators or conspecifics

Alloparental Care

Willingness of an alloparent to invest in or take risk for dependent should be influenced

How Alloparental Care May Increase

1. Alloparents do not have good prospects of reproducing

2. Current offspring are of high value

How Alloparental Care May Decrease

1. Alloparents' future prospects of reproducing

2. Relative value of the current offspring

3. If successful rearing requires multiple caregivers

Nepotism

Directing alloparental care towards kin

Conditions Favorable to Alloparenting

1. Mothers must think safe

2. Social species (small tight groups)

3. Altricial offspring with long dependency

4. Collective and extractive foraging

5. Unpredictable climates

Cooperative Parenting and Fertility

Because of cooperative care, humans have a much higher fertility rate than other great apes

Give morphological evidence that humans have long history pair bonding?

• Not as much sexual dimophrism (ex. Male height, etc)

• No canines

• Human males have lower sperm quality in comparison to other mammals

When did Homo Sapiens emerge

300,000 years ago

When did agriculture emerge

10,000-15,000 years ago