Biological Anthropology Exam 2 Study Guide 

In primate adaptive trends kingdom means what?

Lecture 10

Primate Adaptive Trends

Humans are

∙ Kingdom- Animalia

∙ Phylum- Chordata

∙ Class- Mammalia

∙ Order- primates

∙ Family- hominidae

∙ Genus- homo

∙ Species- sapiens

Primates are Mammals

∙ Ancestral homologies- features primates share with other placental mammals o Mammary glands- produce milk to nourish the young

o Homeothermy- fur for insulation, sweat glands

o Heterodonty- incisors, canines, premolars, molars

o Expansion of the neocortex

o Placenta, long gestation followed by live birth

In primate adaptive trends phylum means what?

o Maternal care of their young

∙ What defines the Order Primates?

o Derived homologies

 Petrosal bulla- the underside of the skull, made or petrosal part  of temporal bone

∙ Non-primates do not have it made of the petrosal part,  

they have t from the squamosal part of temporal bone

 High degree of grasping ability in hands and feet

∙ Opposable thumb and big toe

∙ Most have nails not claws

∙ Sensitive tactile pads with skin ridges on the tips of the  

digits

 Decreased reliance on olfaction (smell) particularly in  

haplorhines  

∙ Olfactory regions of the brain are reduced

In primate adaptive trends class means what?

∙ Haplorhine primates have a significantly higher  Don't forget about the age old question of What is the meaning of a felony?

percentage of pseudogenes among the olfactory receptor  

gene family than do other mammals, this trend is  

especially pronounced in humans

∙ Nasal structures of the skill are reduced

∙ Haplorhines lack a moist naked skin (rhinarium)  

surrounding the nostrils

 Stereoscopic vision and enhanced depth perception

∙ Haplorhines have evolved trichromatic colorvision

∙ Binocular vision

∙ Stereoscopic vision

∙ Trichromatic color vision in Old World monkeys, apes,  

humans and some New World monkeys

∙ Forward facing eyes with an enclosed bony orbit  

(postorbital bar) We also discuss several other topics like What is the meaning of specialty products/services?
Don't forget about the age old question of What does cultural convergence theory argue about globalization and culture?

 Large brain relative to body size throughout all stages of  

development, expanded neocortex

 Primates develop slowly and invest heavily in offspring

∙ Give birth to single offspring with some exceptions and  

invest heavily in them

∙ Longer gestation- takes longer to marinate a mammal  If you want to learn more check out What is the revenue expenditures?

baby lol

∙ Longer infancy and juvenile periods, and delayed  

reproductive maturation

∙ Long lifespan

 Primates are social

∙ Learn from group mates, one reason for long childhood

∙ Maintain close social bonds

Ancestral Homologies

∙ Generalized Body Plan- generalized postcranial anatomy If you want to learn more check out What affects the micro and macroevolution of populations?

o Retention of the collar bone

o Two separate bones in lower arm

o Five digits of the hands and feet

o Quadrupedalism (terrestrial or arboreal)

 Hind limbs and forelimbs of near equal length

 Arboreal species have long tails to aid in balance on top of  branches

 Shoulder blade positioned to side of rib cage and restricted  movement at the shoulder

 Long flexible lower back

o Vertical Clinging and Leaping

 Long powerful hind limbs

 Long flexible back

 Kong fingers for grasping supports when they land

o Suspensory (including brachiation)

 Short hind limbs

 Elongated forelimbs

 Mobile shoulder joint

 Shoulder blade located on the back We also discuss several other topics like What is the nucleosome?

 Long and curved fingers for grasping branches

o Knuckling

 Form of quadrupedalism practiced by great apes

 Wrist joints are stabilized

∙ Generalized dentition

o Heterodonty

Lecture 11

Dental Adaptations

∙ Carnivores- high pointed cusps for tearing meat

∙ Elephants have broad flat surfaces for chewing through tough grasses and  plant materials

∙ Primates- low rounded cusps generalized dentition that allows them to  process most types of food

∙ Generalized features of the primate dentition

o Teeth in the upper jaw and lower jaw

o Bilaterally symmetric

o Heterodont dentition- incisors canines premolars and molars o Anterior teeth- ingestion

o Incisors cut food

o Canines tear food and also have behavioral functions

o Posterior teeth- chewing

o Pre molars and molars- crushing and grinding

o Insectivory- insect eating

o Frugivory- fruit eating

o Folivory- leaf eating

Primate Diversity

Two Orders of Primates!!!—strepsirhini and haplorhini

LARN THE CHART!!!

Suborder Strepsirhini

∙ Tapetum lucidum

∙ Grooming claw- modified nail on second digit  

∙ Tooth comb

∙ Lorisoidea- galagos and lorises

o Africa and Asia

o Bush baby

o Nocturnal

o Varied diets, fruits, flowers, leaves, insects, small mammals o Many show

 Solitary foraging

o Galagos- known for leaping abilities- vertical clinging and leaping o Loris, Potto- slow quadrupedal locomotion, reduced 2nd digits- strong  wide grasp

∙ Lemuroidea- Lemurs

o Madagascar

o Extremely diverse representing 25% of all extant primate genera o Vertical clinging and leaping

 Long powerful hind limbs

 Long flexible back

 Long fingers for grasping supports when they land

∙ Aye-Aye

o Diet specialized for wood-boring insect larvae

Haplorhines

∙ Derived traits of anthropods

o Most are diurnal active in the day

 Lack the tapetum lucidum

o Reduced olfaction, enhanced vision

 Lack the rhinarium

 Eyes more forward facing

o Full postorbital closure

o Lower jaw is fused in most

o Larger relative brain size

o Longer developmental periods

o Increased social complexity

∙ Tarsoidea- Tarsiers, Southeast Asia

o Grooming claw

o Unfused lower jaw

o Nocturnal, small social groups

o BUT!!

 Lack tapedrum lucidrum, rhinarium, tooth comb

 Other derived traits

∙ Adaptations for vertical clinging and leaping

∙ Larger eyes relative to body size, orbit autonomy

∙ Nocturnal predators of small vertebrates

∙ Anthropoidea- New World Monkeys- Platyrrhini, Us, Apes, and Old World  Monkeys

o Quadrupedalism (Terrestrial or Arboreal)  

 Hind limbs and forelimbs of near equal length

 Arboreal species have long tails to aid in balance on top of  branches

 Shoulder blade positioned to side of rib cage

o Platyrrhines, flat nosed

 Broad nose with outward facing nostrils

 Smaller body size

 3 premolars in each quadrant

 All are arboreal

 Some but not all have prehensile tail

 Must have 2 color vision

o Catarrhines

 Narrow nose, downward facing nostrils

 Larger body size

 2 premolars in each quadrant

 Arboreal and terrestrial

 None have prehensile tails

 All have trichromatic vision

o New World Monkeys

 Small bodied

 Omnivorous, insects and plant exudates

 Variety of social grouping patters

∙ Usually only one breeding female

∙ Intense female-female competition with suppressed  

ovulation in subordinate females

∙ Twinning is common

∙ Males are principal caregivers

 Other Monkeys

∙ Diverse group, taxonomy debated

∙ Insectivore- frugivores

∙ Diverse social organization- monogamy night monkeys to  multimale-multifemale

o Old World Monkeys

 Africa and Asia

 Colobine Monkeys

∙ Dietary specialist on mature leaves

 Cercopithecene Monkeys

∙ Arboreal and semiterrestrial species

∙ Dietary omnivores

∙ Cheek pouches

 Sexual Swelling

o Hominoids: Apes and humans

 Loss of the tail

 Relatively large brains and enhanced cognition

 Prolonged development

 Postcranial adaptations for suspensory posture and locomotion  Suspensory  

∙ Short hindlimbs

∙ elongated forelimbs

∙ Mobile shoulder joint

∙ Shoulder blade located on the back

∙ Long and curved fingers for grasping branches

 Hominoids

∙ Gibbons and Siamongs

o Tropical forests of SE Asia

o Smallest of the apes

o Eat fruits

o Monogamous socially

o No sexual dimorphism

o Brachiation

∙ Great Apes

o Borneo and Sumatra

o Large body size

o Show suspensory adaptations but are quadrupedal  

on the ground

o Knuckle walking- form of quadrupedalism practiced  

by great apes

o Wrist joints are stabilized

Lecture 12

Sociology, Reproductive Strategies, and Sexual Selection

Simple Socioecological Model

∙ Food  Female distribution  male distribution

∙ Limiting factor for males is how many females they can access ∙ Females need food for their distribution

∙ Primate Diets

o Primates obtain nutrients from many different sources

 Carbs from fruit and gums

 Fats and oils from animal prey such as insects also nuts and  seeds

 Protein from insect and animal prey and young leaves

o Leaves are also high in fiber which can be difficult to digest- most  colobines (old world monkeys) eat leaves and have enlarged large  intestines

o Insectivores tend to be smaller in body size

 Smaller animals have relatively higher energy requirements, and eat small amounts of high quality food

o Folivores tend to be larger in body size

 Can afford to eat large quantities of lower quality foods

∙ Diets Influence ranging patterns

o Leaves are more abundant in supply, and predictable in space and  time

o Fruits tend to be less predictable in supply and patchily distributes in  space and time

o Folivores tend to have smaller home ranges than frugivores

∙ Why do primates live in groups?

o Costs of sociality

 Greater competition for resources

 Vulnerability to infectious disease

o Two main 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 than lone individuals

o Joint defense of food resources is profitable when

 Food items are relatively valuable

 Food sources are clumped in space and time

 There is enough food within defended patches to meet the  

needs of several individuals

o Fruit often meets these three requirements

o Thus, between-group competition over food resources favor group  living

∙ Larger groups generally are more successful in fights over resources than  small groups

∙ Problems of group living

o Benefits gained in between-group competition are offset by costs from  within-group competition

o RDM doesn’t explain why folivores live in large groups

Predator Defense Model

∙ Group living evolved as a defense against predators

o A wide array of predators hunt primates and predation is thought to be  a significant source of mortality among wild primates

∙ Grouping may reduce vulnerability to predation

o Terrestrial species tend to form larger groups than arboreal species o Solitary haplorhines (orangutans, spider monkeys, etc.) are large in  body size and apparently face little danger from predators

o Juveniles suffer higher mortality in smaller groups than in larger groups o Primates seem to adjust their behavior in response to the risk of  predation

o Weakness of the model- predation is very difficult to observe and it is  therefore difficult to establish whether it is clearly linked in group size

Group Living Summary

∙ At least two major reasons (resource defense and predator defense) primates may live ingroups

∙ Other factors also affect social interactions

Reproductive Asymmetry

∙ Primate mothers are almost always the primary if not exclusive caretakers of  offspring

∙ The behavior of fathers is much more variable

∙ Reproductive Potential = the maximum number of offspring an individual can  produce

∙ Females have limited capacity to increase RS by increase of number of  offspring

∙ Females are best able to increase RS by increase survival

∙ Female Strategies

o Females can improve likelihood of offspring’s survival in 2 ways  Invest more care and energy into offspring  requires food and  other resources

 Be choosy about males fathering offspring only mate with  

quality males

o Females strategies are heavily influenced by the distribution of food in  environment

∙ SCRAMBLE COMPETITION- when resources cannot be easily monopolized o First come first serve

o Resources are low value, highly dispersed, or occur in large patches ∙ CONTEST COMPETITION- occurs when access to a resource can be  monopolized

o Some individuals exclude others and obtain more of the resources  Resources patches are clumped of intermediate size and high  value

∙ Female relationships are influenced by competitive regimes which are a  consequence of food patch size and distribution

Dominance

∙ Often measured as direction of approach-retreat interactions or the direction  of submissive and aggressive behaviors

∙ When there is competition, dominance rank may determine priority access to  preferred resources

∙ Dominance Rank has significant fitness consequences

o Offspring of high-ranking females are large for age (faster growth  rates) and have earlier ages at maturity and first reproduction

o High rank versus low rank

o Begin reproducing earlier  may have an additional offspring compared to lower ranking females

Male Strategies

∙ High variance in reproductive success limited by access to females ∙ Leads to competition among males for mates

∙ Males can increase reproductive success by increasing number of mates ∙ They do this through competition with other males to gain access to mates

Female reproductive success is limited primarily by access to important resources  necessary for survival

∙ Female strategies are primarily influenced by the distribution of food

Male reproductive success is limited primarily by the availability of mating  opportunities

∙ Male strategies are primarily influenced by the distribution of fertile females Reproductive Asymmetry- Males

∙ Fertile females, clumped versus dispersed in both space and time ∙ Females slumped- monopolization of fertilization possible (one male groups) ∙ Females Dispersed or Synchronous breeders- difficult to guard and  monopolize (pair bonds, multimale groups)

Lecture 13

Male Reproductive Strategies

∙ Mating with multiple females when females and resources are distributed in  groups

∙ Pair bonds when females and resources are distributed sparsely Social Organization

∙ Female versus male philopatry

o In female pholopatric groups, related females tend to have high degree of affiliation and territorial defense

∙ Solitary

∙ Pair living

∙ Group living

o Single female- multi male

o Single male- multifemale

o Multi male- multifemale

∙ Mating System

o Monogamy

o Polygyny- one male and multiple females

o Polyandry- female with many males

o Polygynandry- all! Promiscuous!

∙ Social organization and Mating System are not the same

Reproductive Strategies and Social Behavior

∙ We see diversity in these social grouping patterns even within closely-related  groups of primates such as apes

∙ Solitary

o Orang social structure strongly tied to erratic food supply

o Females live with their offspring males are solitary

∙ Monogamous pairs

o Little sexual selection

o Males do not invest much energy in courtship or mating

o Males invest heavily in their offspring and in maintaining long term  bonds with their mates

o Marmosets and Gibbons

∙ One Male, Multi Female Groups

o Males compete actively to establish residence in groups of females o Resident males face constant pressure from nonresident bachelor  males; threat of aggression

o Infanticide- important part of intrasexual competition in these groups  Male strategy for increasing opportunities to sire offspring

o Lactation ends abruptly, females become sexually receptive almost  immediately

∙ Multimale, Multifemale

o Larger groups of females, one single male cannot monopolize access to all of them

 Male-male competition is mediated through dominance  

relationships

o Male dominance rank is associated with reproductive success in many  studies

o Female preferences can influence male mating success

Social Structure Summary

∙ Primates vary widely in their social structures

∙ These are influenced by a variety of factors, including distribution of food  sources which impacts social behavior according to socioecological model

Sexual Selection

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

∙ Favors the evolution of traits that give individuals an advantage in mating  competition

∙ Darwin- Differences in reproductive success caused by competition over  mates  sexual selection

∙ Intersexual selection

o Occurs where individuals exert choice among individuals of the  opposite sex for mating partners

 Favors traits that make males usually more attractive to females ∙ Intrasexual Selection

o Competition among same-sex individuals for access to members of the opposite sex

 Favors large body size, large canine teeth, and other traits that  enhance competitive ability

o Contest competition for mates traits that improve fighting success  Selection for large male size body sexual dimorphism

 Selection for large male canine size canine dimorphism

o Sexual dimorphism

 When males and females differ consistently in size and  

appearance

 Greatest in one-male, multifemale polygynous social groups  Least in monogamous social groups

 Gibbons, siamangs  

o Sperm competition

 In social systems where there are multiple males have access  and male-male competition is high, sexual selection favors  

sperm competition

o Infanticide

 Act of killing a dependent infant

 One male groups most common

 Outsider males overthrow the resident dominant male and a  new leader male is established

 This may be followed by killing of unweaned infants by the new  leader male

∙ Intersexual Selection

o Where individuals exert choice among individuals of the opposite sex  for mating partners

o Favors traits that make males usually more attractive to females

∙ Intrasexual Selection

o Competition among same-sex individuals for access to members of the opposite sex

o Favors large body size, large canine teeth, and other traits that  enhance competitive ability

∙ Intersexual Selection

o Species in which females can choose the partners with which they  mate, selection favors traits that make males more attractive to  females

o Favors traits that

 Provide direct benefits to their mates

 Indicate good genes and thus increase the fitness of the  

offspring

 Make males more conspicuous to females, although they can be  maladaptive  

Human Mate Choice

∙ Humans are most socially monogamous

∙ Many human societies have different mating systems (monogamous,  polygynous, polyandrous, serial monogamy etc.)

∙ Humans choose mates on the basis of many factors, but some of them may  be rooted on our evolutionary past

∙ Symmetry: honest indicator of the quality of someone’s genes, honest signal:  information increases the fitness of the receiver  

∙ Major histocompatibility complex

o Proteins that allow immune system to detect foreign invaders o Greater genetic diversity in MHC may allow for more robust immune  response

∙ Humans select mates on the basis of odor cues, which indicate genetic  diversity at important immune function loci  

Primates choose mates base on MHC diversity

∙ Rhesus Macaques

o Males that were heterozygous at a MHC locus sired significantly more  offspring than homozygous males  increased fitness

∙ Pig-Tailed Macaques

o Similarity in MHC antigens between mother and father predicts  pregnancy loss

Behavior is shaped by natural selection

∙ Violent gorillas that commit infanticide will have more offspring than pacific  gorillas that don’t  offspring will inherit the violent behavior  infanticide will  evolve

∙ Dedicated marmosets that invest in parental care will have more successful  offspring that indifferent marmosets that don’t  stable bonds and male  parental care will evolve

∙ ** Humans continue to evolve- we aren’t stuck in the past any more than  other species are, we are still evolving**

∙ Naturalistic Fallacy- just because something occurs in nature- doesn’t make it  good or desirable

∙ Culture is a powerful source in human societies

o Many studies are based on weird societies- and may not reflect human  behavioral universals

Lecture 14

Fossils

Paleontology- study of extinct organisms based on their fossilized remains Fossil- the preserved remains of once-living organisms

Process on how fossils become fossils*****

What is a fossil?

∙ Fossilization is a rare event

∙ Several conditions must be met before remains can be preserved o Remains must be suitable for fossilization

o Remains must be buried

o Material in which the remains are buried must be suitable for  fossilization  

What can we learn from fossils?

∙ Cranial size cognition behavior

∙ Teeth diet, behavior, social structure

∙ Body proportions ecology

∙ Hands manual dexterity

∙ Pelvis spine and lower limbs locomotion, obstetrics

∙ Feet bipedalism

Some unusual Surprises

∙ Footprints

∙ Individual walked across volcanic ash layer

∙ Soft rain cemented the footprints, and they were covered by another ash  deposit

∙ Information about locomotion

Some Unusual surprises

∙ Coprolites (fossilized feces)

∙ More common when individuals incorporate inorganic components into their  diets—hyenas eat bones

∙ Useful to understand diet and environment

The Matrix

∙ Skeletons become fossils by absorbing minerals from their surroundings ∙ The matrix composition is informative for analyzing fossils and it is critical for  the dating of fossils

∙ Context is critical

Three Majors types of Dating

∙ Relative dating

o Using principles of stratigraphy

o Biochronology (faunal succession)

∙ Absolute dating

o Radiometric methods

∙ Paleomagnetism  

o Method for linking up to absolute dating methods

Relative Dating

∙ Most fossils found in sedimentary rocks  

∙ Deposited by movement of water

∙ Basic Stratigraphy

o Stratigraphic Laws  

 Original horizontality

 Lateral continuity

 Superposition

 Cross-cutting relations

 Law of faunal succession

∙ From a couple centuries of paleontology, we know a lot  

about what critters occur when and where

Radiometric Dating

∙ Atomic Structure

o Protons- positive charge, determines element

o Electrons- negative charge

o Neutrons- no charge

∙ Isotopes of Carbon

o Carbon 14 is radioactive

∙ MISSED SOME

∙ Carbon 14 Dating

o Estimate age based on proportion of remaining 14C

∙ Potassium- Argon dating

o Based on the decay of 40K and 40 Ar

o Argon gas escapes magma but starts accumulating as magma cools  and hardens

o Volcanic ash

Magnetostratigraphy

∙ The Earth is a magnet

∙ In the geological past, there were times when a compass would have pointed  the opposite direction from today

∙ Magnetic “barcode”- pattern of reverse and normal polarity help link  unknown sections to known timescale

Lecture 15

Primate Fossil Record

Continental Drift

∙ Earth’s crust is formed by continental plates that float and move on the  mantle

∙ You get earthquakes and mountains with crustal plates moving- key features  in shaping earth’s surface

∙ Position of continents has changed throughout time

∙ Pangea  Laurasia and Gondwana more splitting off  today ∙ Position of the continents influence the movement and distribution of animal  species, including primates

∙ Distribution of continents influences climate

Temporal and Climate Context

∙ Cenozoic time period- mammals

∙ Overall cooling and drying trend during the Cenozoic

∙ *know order of time eras. And overall what was going on during those times* How would you recognize an early primate? What traits would you look for?

∙ Where do we see these traits occurring?

o Petrosal bulla

o Derived hands and feet

o Grasping

o Nails

o Decreased reliance on smell

o Forward facing eyes, etc.

Adaptive Origins of Primates

∙ Hypothesis:

o Arboreal Hypothesis

 Primate characteristics such as grasping hands and feet, nails,  and stereoscopic vision evolved as adaptations to the arboreal  

lifestyle of early primate ancestors

 BUT- primate ancestors were already arboreal, so arboreality  alone is not enough to explain adaptations

 Many other extant arboreal mammals lack primate  

specializations

∙ Arboreality alone can’t fully explain distinctive primate  

traits

o Visual predation

 Visually-guided predators

 Cats, owls—spot prey with eyes and use precision strikes on  prey

 Primate visual specializations and other distinctive primate traits evolved as adaptations for stalking and grasping insect prey in  the terminal branches of trees

 Reduction of olfaction would be a secondary result of orbits  

coming together

o Angiosperm exploitation

 Primates co-evolved in concert with the adaptive radiation of  flowering plants, to exploit their products (fruits, flowers, nectar) and the insects that feed on them in a small branch setting

 Evolution of angiosperms

∙ Before the cretaceous- gymnosperms

∙ After the cretaceous- angiosperms

∙ New resources—flowers and fruits

∙ Consensus view incorporates ideas from the visual predation model and he  angiosperm model

∙ Consistent with fossil evidence showing that earliest primates were nocturnal  and had adaptations for insectivory and fruit-eating

Evolution of Primates: Family Tree

∙ * there is a family tree picture *

Paleocene: Plesiadapiformes

∙ Primitive, they retain a number of ancestral mammalian traits ∙ Some plesiadapiformes possessed some but not all derived primate traits ∙ Not clear if they fall within or just outside of, the primate evolutionary tree ∙ Paleocene- 65-55 mya

Eocene

∙ 55-34 mya

∙ “dawn” – mammals we know today diversified

∙ 1st true primates occurred- Adapoids and Omomyoids

∙ First Primates of Modern Aspect

o Adapoids

 Elongated snout

 Many were diurnal- small orbits

 Lack derived features of strepsirrhines or haplorrhines

 Probably ancestral to strepsirrhines

o Omomyoids

 Short snout

 Large orbits suggest nocturnality

 Small, primarily insectivorous

 Possible relationship with haplorrhines

 Earliest true primates appeared in Eocene epoch

Oligocene

∙ 35-24 mya

∙ Anthropoid Origins

o Marked cooling and drying trend at the end of Eocene

o Extinction of certain species and evolution of new ones

o The Fayum (South of Cairo- by the Nile)

 Today it is a dessert

 In Eocene-Oligocene there was water and rhinos and diversity of  mammals

 A major trait that distinguishes between old world and new  

world monkeys- the teeth 2-1-2-3 is what we have- 2-1-3-3 new  world monkeys (need to know this)

 Genus Apidium- small bodied arboreal quadruped, small brain,  diurnal

∙ 2-1-3-3 dental formula  indicative of its evolutionary  

position before NW monkeys divergence

∙ How did this monkey get from Africa to South America???  

There is an ocean???

o There is a rafting theory- they rafted across the  

ocean—S America and Africa were closer together

moved apart slowly

o The arrival of the New World Monkeys in South America

 Ancestors of NW monkeys originated in Africa and rafted across  Atlantic Ocean- Caviomorph rodents also appear suddenly

 Ancestors of NW monkeys could conceivably be North American  Primates- but no fossils support this and this would require  

independent evolution of monkey traits

o Genus Aegyptopithecus- Fayum

 Medium size arboreal

 Diurnal

 Frugivorous

 Small brain

 Derived catarrhine dental formula- loss of 2nd molar 2-1-2-3

 Postdates divergence of NW monkeys and shares affinities with  OW anthropoids

Miocene

∙ 24-5 mya

∙ * ape tree picture *

∙ Extant Apes

o Locomotion underneath branches- large size corresponding  postcranial adaptations

o Monkeys above branches and apes below branches

o No tail

o Long flexible arms

o More vertical posture

o Larger brains

∙ Ape localities

∙ Ape diversity

o Approximately 100 ae species during the miocene

o In Europe, Asia, and Africa

∙ Early African Morotopithecus and Proconsul

o Derived hominoid features

 larger relative brain size

 Shorter snout compared to Aegyptopithecus

 Y-5 molars

 Lacked a tail

 The postcranial skeleton indicates that Proconsul was  

quadrupedal and lacked derived features for suspensory  

locomotion

 Good candidates to represent anatomy of the last common  ancestor of apes and humans

∙ Ape Y-5 molar pattern, OW Monkey- biophodont molars

∙ Miocene: Asian forms, Sivapithecus

o Many features of the skull suggest a close evolutionary relationship  with orangutans

o Postcranium suggests quadrupedal locomotion

∙ Hominoid Diversity- Gigantopithecus

o Largest primate that has ever existed more than 1000 lbs and 10 ft o Coexisted with homo erectus for some time

Evolutionary History of the Apes

∙ Many different species with unclear evolutionary relationships ∙ Sivapithecus or similar forms likely ancestors of orangutans ∙ Some European and Asian species might be ancestral to African apes

Decline of Miocene Hominoids

∙ Climate changes in the late Miocene (cooler and dryer climate) ∙ Too slow generation time and developmental period to deal with these  climatic changes

∙ The same climatic conditions favored the evolution of the earliest ancestors  of the human lineage