Exam 2 - GWU Bio Anth (Spring '24)

Primates

are mammals

Traits of mammals

mammary glands, homeothermy, heterodonty, expansion of neocortex, placenta

Ancestral Traits

features primates share with other placental mammals

Monotremes

egg-laying mammals

Marsupials

live birth mammals

Eutherians

placental mammals

What defines primates?

diversity (size, habitat, socially, diet)

Strepsirrhines

lemurs, lorises/galagos

Haplorhines

Tarsiers, Monkeys of Americas, Monkeys of Asia/Africa, Apes

Petrossal Bulla

the single trait that characterizes all primates, to the exclusion of all other mammals

Derived Traits of Primates

petrosal bulla / grasping ability (opposable thumbs, nails, pads) / decreased reliance on smell / reduced nasal structures (no rhinarium, moist skin) on nose) / stereoscopic vision / forward facing eyes with postorbital bar / large brain relative to body size / long life history, single offspring / social

Ancestral Traits of Primates

generalized body plan (collar bone, separate bones in lower arm, five digits on hands & feet) / generalized dentition

Locomotor Adaptations

Quadrupedialism / Vertical Clinging & Leaping / Suspensory / Knuckle Walking

Quadrupedialism

hind & forelimbs of near equal length / arboreal species have long tails to balance / restricted movement at the shoulder / flexible lower back

vertical clinging and leaping

long powerful hind limbs, long flexible back, long fingers for grasping

Suspensory

short hindlimbs, elongated forelimbs (mobile shoulder), shoulder blade on the back, long and curved fingers

Knuckle-Walking

form of quadrupedialism by great apes / wrist joints stabilized

Primate Dental Adaptations

low, rounded cusps: generalized dentition

General Features of Primate Dentition

teeth in upper & lower jaw, bilaterally symmetric, heterodont dentition (ICPM) / 2.1.2.3 EXCEPT for Platyrrhines & Strepsirrhines (2.1.3.3)

Primate Distribution

over 400 species of primates across the world

Stepsirrhines

lemurs + lorises & galagos

Ancestral Traits of Strepsirrhines

good smell (wet rhinarium), non-fused mandible, eye with tapetum lucidum (nocturnal)

Derived Traits of Strepsirrhines

Nails, but grooming claw on 2nd digit of hind limb / tooth comb / postorbital bar

Lemurs

found in Madagascar / extremely diverse activity, diet, and social systems / vertical clinging & leaping

Lemur Special Case

Aye-Aye - digits have claws, where one acts as a skewer to work its specialized diet of wood-boring insects

Galagos

In Africa, known for leaping abilities - nocturnal, varied diets, solitary or in pairs

Loris

Africa, known for slow quadrupedal locomotion ; strong and wide grasp

Derived Traits of Anthropoids

diurnal (lack tapetum lucidum) / lack rhinarium (reduced smell) / forward facing eyes (enhanced vision) / full postorbital closure / fused lower jaw / larger brains / longer developmental periods

Tarsiers

Southeast Asia - grooming claw, unfused mandible, nocturnal / lacks tapetum lucidum, rhinarium, tooth comb / vertical clinging, large eyes to body size, predators of small vertebrates

Platyrrhine Monkeys

Americas -- broad nose / smaller bodies / 3 premolars / arboreal / some have prehensile tail / most have 2 color vision

Cercopithecoid Monkeys

found in Africa & Asia --- narrow nose, downward facing nostrils / larger bodies/ 2 premolars / arboreal & terrestrial / no prehensile tails / all have trichromatic vision / ischial callosities (pads on their rears)

Dental Adaptations for Insectivory

sharp crests for puncturing the exoskeleton of insects

Dental Adaptations for Frugivory

low cusps for crushing soft fruits

Folivory

shearing crests for cutting tough leaf material into small pieces

Platyrrhine exception

Owl Monkey (only nocturnal monkey)

Marmosets/Tamarins

small bodied / omnivorous, insects & plants / variety of social patterns -- usually only one breeding female

Capuchins

use tools / large brains / slow life

Golden Faced Saki

Dental specializations for eating hard nuts

Spider Monkey

prehensile tails; highly suspensory

Colobine Monkeys

eats mature leaves (deep jaw, complex stomach) / arboreal quadrupeds

Cercopithecines

arboreal & semiterrestrial / omnivores / cheek pouches / female hindsides have sexual swelling to attract attention from males

Apes

large body size / no tails / build nests / large brains / prolonged development / postcranial adaptations for suspensory posture & locomotion

Gibbons & Siamangs

Tropical Forests of SE Asia / smallest of apes (lesser apes) / eat fruits / monogamous / low sexual dimorphism / brachiaction (swings from arms)

Orangutans

SE Asia / 3 species / solitary, men alone, females w offspring / large overlapping ranges / large bodies (medium sexual dimorphism) / mostly arboreal / quadrupedal

Gorillas

2 species / found in Africa / very large bodies (high sexual dimorphism) / folivores / live in large groups with a dominant male

Chimpanzees

Africa (multiple terrains) / diverse diets (group hunting, tool use) / human-like body size / multi-male; multi-female groups (females leave home group instead of males) / lots of inter-group aggression

Bonobos

DR Congo / diet like chimps except more vegetation, no hunting / slightly smaller than chimps / multi-male;multi-female groups w female bonding / use sex to avoid conflict

Insectivore Body Size

smaller with higher energy requirements - eat small amounts of high quality food

Folivore Body Size

larger - eat large quantities of lower quality food

Diets Influence ...

Ranging patterns -- leaves more abundant, fruits more patchy

Costs of sociality

greater competition for resources / vulnerability to disease

Benefits of Sociality

enhanced access to resources / reduced vulnerability to predation

Resource Defense Model

primates live in groups because groups are more successful in defending access to resources (occurs often when food items are valuable and groups are close in proximity)

Problems with RDM

benefits gained are offset by costs / doesn't explain why folivores live in large groups

Predator Defense Model

group living evolved as a defense against predators

Problems with PDM

predation is difficult to observe, so we cannot establish whether it is linked to group size

Cultural Traditions

learned behaviors and practices passed down through generations within a social group

Social Learning

learning through observation, imitation, communication / occurs within social groups

Tool Use

tool use is passed down culturally / innovation reflects cultural adaptations

Social Organization

Solitary / pair living / group living (SM-MF, SF-MM, MM-MF)

Mating Systems

Monogamy, polygyny, polyandry, polygynandry

Solitary Primates

Orangutans - tied to erratic food supply

Pair Living Primates

Marmosets, Tamarins, Gibbons - males invest heavily in offspring and bonds with mates

One Male, Multifemale Groups

Hamadrydas Baboons - males compete to establish residence in groups of females

Multimale-Multifemale Groups

groups where dominance comes into play

Dominance

measured as direction of approach-retreat interactions

Contest Competition

Occurs when access to a resource can be monopolized (individuals can be excluded)

Scramble Competition

when resources cannot be monopolized, they become first come, first serve

Reproductive Asymmetry

a difference in reproductive potential - females are best able to increase reproductive success by increase survival

Female Strategies for Reproductive Success

1. invest more care & energy into offspring / 2. only mate with 'quality' males (influenced by distribution of food)

Male Strategies of Reproductive Success

increase success by increasing number of mates (often difficult in groups) (influenced by distribution of females)

Sexual Selection

a form of natural selection that occurs when individuals differ in their ability to compete with others for mates or to attract members of the opposite sex

Intrasexual Selection

competition among same-sex individuals for access to members of the opposite sex (favors large bodies, canines)

Intersexual Selection

when individuals exert choice among individuals of the opposite sex for mating (favors traits that make males more attractive)

Sperm Competition

when mating is promiscuous, selection favors increased sperm motility and production

Infanticide

when an outsider male overthrows the resident male and kills his children

Symmetry

honest indicator of the quality of someone's genes

Honest Signal

trait that gives a truthful impression of an individual's fitness

Handicap Principle

individuals with nonfunctional, ostentatious traits show off survival skills whilst bearing a handicap

Paleontology

the study of extinct organisms based on their fossilized remains

Fossils

the preserved remains of once-living organisms

Formation of Fossils

Organism dies / gets covered by water and sediment / sediments fossilize the bones / erosion exposes the layers containing bones

Conditions for Fossilization

remains suitable for fossilization / remains must be buried

The Matrix Composition

helps analyze and date fossils

Relative Dating Methods

strategies that use geological context and rock layers to establish ages between localities and the fossils found there

Law of Superposition

sedimentary layers are deposited in a time sequence, with the oldest on the bottom and youngest on top

Lithostratigraphy

uses characteristics of the rock layers to link sedimentary sequences and establish relative ages across sites

Tephrostratigraphy

uses chemical similarities of volcanic ash layers to determine time equivalence across sites

Biostratigraphy

uses the organisms themselves -- especially index fossils-- to establish relative ages across sites

Absolute Dating

technique to estimate the age of a fossil in absolute terms, through the use of a natural clock, such as radioactive decay

Isotopes

radiocative forms decay into stable isotopes at a predictable rate (half life can be used to determine time since death)

Paleomagnetism

uses changes in the earth's magnetic polarity to establish age

Continental Drift

the position of continents has influenced the movement of animals species and the climate over time

Arboreal Origin Hypothesis

primate characteristics evolved as adaptations to the arboreal lifestyle (bad hypothesis since primate ancestors were already arboreal)

Visual Predation Hypothesis

primate visual specializations evolved as adaptations for hunting prey in trees -- reduced olfaction

Angiosperm Exploitation Hypothesis

primates co-evolved with the adaptive radiation of flowering plants, to exploit their products and the insects feeding on them (needed traits in order to reach the fruit)

Major Evolutionary Novelties of Humans

bipedalism, characteristics of dentition, elaboration of material culture, increase in brain size, long lifespan

Mosaic Evolution

different traits evolve at different points in time (like human traits)

Human Dentition

2.1.2.3 formula, Y-5 molar pattern

Canine Reduction Effects in Humans

Humans have smaller canines than apes because of different social interactions / loss of diastema / less sexual dimorphism / a parabolic dental arcade