Lecture 6: Primate Origins: Rise of the Primates

Microevolutionary - Forces affect the gene pool – Change within a single reproducing population

Macroevolution – Larger scale, speciation events

  • Creation of new species over time

Divergent – Single ancestor giving rise to 2 descendant species

  • Physical and social barriers

Convergent – Two photogenically unrelated organisms develop greater similarities

  • Based on homoplasy
  • Not indicative of evolution

Homologies - Indicative of evolutionary relationships, analogies are not


Systematics vs Cladistics

Systematics – Traditional approach

  • Categorize organisms based on homologous traits

Cladistics – Determine ancestral versus derived (modified) homologous traits to determine lineage

  • Clade - A group of organism with a common ancestor
  • Can get a better idea between the relationships
  • Group of organisms that come from a common ancestor

Ecological Niche – A species way of life considered in the context of its environment (Haviland & Crawford, 2009:139)

  • Environment is what gives the context in every species’ life

Adaptive Radiation – Rapid diversification of an evolving population as it adapts to a variety of available niches (Haviland & Crawford, 2009: 138)

  • Rapid dissemination of a group of organism
  • Occurs before every major human evolutionary event in human evolution – before a new species comes up we have a major climatic event that could lead to major extinction of many species and will open up a new environment for new species
  • With each global climatic event we see the exploitation of species

Major Periods & Epochs of Evolution of Life

Paleozoic – Permian Period

  • 280 million years ago
  • Permian Deposits show mammal–like reptiles
  • Slimmer
  • Flesh eaters
  • Reduction in bones
  • Shifting limbs
  • Beginning of separation between mouth & nasal cavity
  • Dental differentiation


Mezozoic (Triassic, Jurassic, Cretaceous Periods)

  • Reptiles prominent land vertebrates (Dinosaurs)
  • 1st mammals appeared - End of triassic period (190 million years ago)
  • Small flesh eaters
  • Nocturnal
  • Enhanced smell & hearing
  • Enlarged cerebral cortex
  • Loss of color vision


Cenozoic (Age of Mammals)

  • Including 1st appearance of Primates
  • Associated with Large Climatic change
  • Separation of continents away from equator
  • From dry environment to tropical, dry, arid environment
  • More pollen – producing plants
  • Cooler temperatures
  • Tropical & subtropical forests
  • Dinosaur extinction – Debateable
  • Changing ecological niche
  • Radiation of new varieties of plants
  • Proliferation of deciduous forests
  • Mammalian adaptive radiation


Paleocene Primates

  • 65 million years ago


Suborder - Plesiadapiformes

  • Extinct mammal – Common ancestry with primates
  • Squirrel like Insectivore
  • Flexible digits, wrists, ankles
  • Probable origin of primates
  • Reminiscent of a flying squirrel - Many people believe that
  • Could be an example of convergence that shows arborealism
  • WY discovery – Carpolestes – Plesiadapiforme who is very adaptive of former primates
  • Lived 55 million years ago in North America
  • Darwinius – Most complete of all of the early primates – 50 million years

Who is the definitive first member of primates? Not plesiadapiformes

1st primate - 60 million years ago

Fossil evidence - Morocco

  • Dentition similar to modern mouse lemur (Strepsirhine)


Eocene Primates

  • 55 to 34 million years ago


Age of the Prosimians

Lemur, Loris, Tarsier

Primate characteristics -

  • Complete postorbital bar
  • Larger frontal lobe
  • Nails
  • Forward placed eyes
  • Slightly reduced snout
  • Limbs for grasping & leaping
  • 3.1.4.3 dental formula
  • 2 families - Adapidae and Omomyidae


2 Families -

1. Adapidae (Similar to Lemurs & Lorises)

  • Mostly diurnal
  • Ate fruit & leaves


2. Omomyidae (Tarsier-like)

  • Nocturnal
  • Probable ancestors of tarsiers
  • Achilles – Species found in China 55 million years ago – Beginning of the Eocene
  • May be the first haplorrhine
  • Tarsiers are considered haplorrhines
  • Demonstrates split between strep and hap 55 mya
  • Eat fruit & insects
  • Hind limbs slightly longer than forelimbs


Catopithecus - late eocene

  • 37 million years ago

Fayum, Egypt - Several skulls, teeth, jaws


Catarrhine like

  • Walled eye orbit (Enclosed postorbital septum)
  • May be the first evidence of anthropoids
  • Somewhat forward foramen magnum
  • Rounded cusps on molars
  • Catarrhine dental formula = 2.1.2.3

Primitive strepsirhine features (Lemur like) -

  • Small brain
  • Long snout


Oligocene (Monkeys & Apes)

  • 34 to 23 million years ago
  • Old world and new world monkey ancestors

2 families -

1. Parapithecidae - resemble platyrrhine monkey

  • Apidium – Genus
  • Almost all of the evidence from all of oligocene is found in Fayum depression, Egypt
  • Most prolific of all is the Apidium – Perhaps the ancestor to before the catarrhine and platyrrhine split
  • Key thing - New world monkeys have an extra molar – must have originated prior to their specialization
  • Dental formula 2.1.3.3.
  • Diet of fruit & seeds
  • Small arboreal quadruped
  • Leaping & springing


2. Propliopithecidae – Old world anthropoid - Resemble generalized catarrhine

  • Dental formula 2.1.2.3
  • Small to medium in size
  • Likely fruit eaters

Genera - Aegyptopithecus - Probable ancestor of hominoids

  • Most completely represented & significant fossil genera from Fayum
  • Preceded the major split in catarrhine evolution (Prior to divergence between OWM & Hominoids) – May be the common ancestor between old world monkey and hominoid


Miocene

  • 23 to 5 million years ago
  • Proliferation of Apes
  • Age of the hominoids

Divided into early, middle and late miocene

Early Miocene (23-17 million years ago)

  • Proconsul (East Africa)
  • Possible ancestor of all hominoids


Middle Miocene

1. Dryopithecus (12-9 Million Years Ago)

  • Europe
  • Ancestor of all apes?
  • Ape-like traits
  • Postcranially - Arboreal brachiation & suspension
  • Cranial shape
  • Resembles the African great ape
  • Thin enamel on teeth

2. Sivapithecus (13-7 Million Years Ago)

  • South Asia
  • Similar to orangutan in face
  • Most evolutionary anthropologist agree that this is the common ancestor to orangutans
  • Postcranially - Resembles proconsul – Different from orangutans


Late Miocene (10-5 million years ago)

1. Lufengpithecus

  • South China
  • Large miocene ape
  • Shares features with dryopithecus

2. Gigantopithecus

  • Southeast Asia
  • Pleistocene Ape
  • 1800 - 10000 years ago
  • Largest primate that ever lived
  • Heating up of the world at the end of the Miocene


Pliocene – Age of Hominins

Who were the earliest hominins?


HOMININ ORIGINS

What differentiates our hominin ancestors?

  • Large brain size (encephalization)
  • Dentition
  • Tool making behavior – standardized
  • Habitual BIPEDAL LOCOMOTION
  • Example - Eoanthropus Dawsoni (Piltdown Man) – Believed to be the missing link until after his death
  • Found out it was a hoax, human skull with an orangutan mandible attached to it


Human Bipedalism – HALLMARK OF EVOLUTION IN HOMININS

  • Ability to walk on two legs
  • Moved from C-shaped spine to an S-shaped spine
  1. Forward foramen magnum
  2. Spine
  3. Basin pelvis
  4. Long lower limbs
  5. Valgus position
  6. Foot changes


Advantages of Bipedalism

  • See farther
  • Travel long distances
  • Freed the hands


Disadvantages of Bipedalism

  • More visible to predators
  • Expose underbelly
  • Limits ability to change direction
  • Reduces speed
  • Lower backaches
  • Leg & foot injury


Who were the earliest hominins?


Who were the Three contenders of the origins of hominins?

1. Sahelanthropus tchadensis, Chad 7-6 Million Years Ago

  • Skull
  • Unique features not seen on miocene apes


2. Ardepithecus, Aramis, Ethiopia 4.4 Million Years Ago (Reassigned to 5.8-5.2 Million Years Ago)

  • Dentition reminiscent of Chimps
  • Hominin features
  • Forward foramen magnum
  • Bipedal?


3. Orrorin tugenesis, 6-mya

  • Bipedal?
  • May have a valgus angle in the femur

Australopithecines – First definitive hominins of the Pliocene.

  • Ape-like from waist up
  • Longer arms relative to legs;
  • Curved flexible fingers and toes
  • Still tree climbing
  • Forward thrust of the face,
  • Large flaring cheek bones-ape like
  • Human like from the waist down
  • Bipedal - S spine; forward foramen magnum; basin shaped pelvis


Gracile Forms

  • Generally have ape shaped face

East Africa

  1. A. Anamensis
  2. A. Afarensis


South Africa

3. A. Africanus


Robust Forms (Paranthropus)

East Africa

  1. A. Boisei
  2. A. Aethiopicus


South Africa

3. A. Robustus

  • Yellow – Chimp, Middle – Lucy, Right – Human
  • Short wide iliac blade – Left and mid
  • Lucy to the chimp – Chimp has an elongated iliac blade (long and narrow)– Posterior
  • Shorter ischium – Pulled up and shortened in lucy and the human


Gracile Australopithecines

Three Species - Anamensis, Afarensis, Africanus

Cranial anatomy -

  • Generally ape-like

Dentition -

  • Human-like (Thick enamel)
  • Arcade – Ape-like

Post cranium -

  • Apelike waist up
  • Human waist down
  • Australopithecine has pelvis similar to modern human


Australopithecus Anamensis

  • 4.2 to 3.9 Million Years Ago
  • East Africa Kenya
  • Ape-like jaw and cranium
  • Thick enamel on dentition
  • Bipedal


Australopithecus AFARENSIS

  • 4 to 2.9 Million Years Ago
  • Original Discovery - Hadar, Ethiopia


DON JOHANSON

1. Lucy (Found in 1974)

  • Almost 40% of adult skeleton
  • Female by pelvis
  • Stature 3 ½ to 4 ft

Most complete gracile australopithecine to have been found.


2. The First Family (1975)

  • At least 13 individuals
  • Including 4 infants


3. Fossilized Footprints

  • Embossed into an ancient volcanic tuff
  • Approximately 4 to 3.5 Million Years Ago
  • Mark Leakey (1978)
  • Laetoli, Tanzania - Footprint path; Can be dug by potassium/argon dating


Specific Characteristics of A. afarensis (in comparison to the S. African gracile species)

Ape-like cranium -

  • Strong facial prognathism (Long snout)
  • Small cranial capacity (Average 420cc) 310-500 cc

Ape-like teeth -

  • Relatively large incisors
  • Relatively large canines (Compared to modern humans)
  • Ape like shaped dental arcade (Parallel rows)


AUSTRALOPITHECUS AFRICANUS

Original Find - Raymond Dart (1924) Taung, South Africa

Taung Child

  • Estimated to be 3–4 years of age at death (Development more similar to apes than humans)
  • S. African Gracile Australopithecine
  • Brain - 405cc

Specific Characteristics of A. africanus (in comparison to A. afarensis) -

Dentition

  • Small incisors and canines
  • Rounded dental arcade

Cranium

  • Larger cranial capacity than A. afarensis
  • More globular cranium


Robust Australopithecines (Paranthropus)


Limbs/Locomotion

  • Bipedal
  • Thick bones - Prominent muscle markings


Cranial Anatomy

  • Sagittal crest – Lateral muscle
  • Broad vertical face
  • Massive brow ridge
  • Broad, jutting cheek bones
  • Nuccal muscle


Diet and Dentition

  • Large palate and premolars
  • Massive flat molars, with crowding of the front teeth
  • Deep jaws
  • Herbivore


AUSTRALOPITHECUS AETHIOPICUS

The Black Skull

  • Lake Turkana, Kenya, East Africa
  • 1985, 2.5 Million Years Ago


Hyper Robust

  • Broad face
  • Sagittal connects to the nuccal – Unique feature of aethiopicus
  • Massive projection of the upper face
  • Very large palate
  • Large area back teeth


Primitive Traits

  • Cranial Capacity - 410 cc
  • Compound crest
  • Prognathic (Long snout)
  • Round dental arcade


AUSTRALOPITHECUS BOISEI

First Find

  • Olduvai Gorge (1959)
  • Mary Leakey
  • Originally called “Zinjanthropus Boisei” by Louis Leakey
  • 1.75 Million Years Ago


Characteristics of A. boisei

  • Large body size (34 – 49 kg)
  • Bones thick and robust


Cranial Anatomy/ Brain

  • Heavy and massive skull
  • Cheek bones flare out to the sides
  • Sagittal & nuchal crest
  • Prominent brow ridges
  • Postorbital constriction (behind the eyes)
  • Cranial capacity 500 – 530 cc - larger than the gracile


Diet & Dentition

  • Massive palate & premolars
  • Large flat premolars and molars


AUSTRALOPITHCUS ROBUSTUS

  • South Africa
  • First Find - Kromdraai & Swartkrans, Broom & Robinson (1948)
  • Dating is not definite - Thought to be anywhere from 1.8 to 1 Million Years Ago

Characteristics of A. robustus

Limbs and locomotion

  • Body size similar to A. Africanus (32-40 kg)
  • Thick bones & prominent ms markings
  • Bipedal

Cranial Anatomy / Brain

  • Flattened “dished out” face
  • Face positioned high with a low forehead
  • Anteriorly positioned cheek bones
  • Sagittal crest – Smaller than A. Boisei, and compound as in A. aethiopicus
  • Cranial capacity of approx 530 cc (450-550 cc)
  • Large mandible

Dentition

  • Large flat molars (Not in proportions as great as in A. boisei)


What is the relationship between the australopithecine species?

Which one leads to the genus Homo?


We know that -

There are Five contenders

  • There are at least 2 separate hominin lines between 3 to 1 Million Years Ago
  • Robust australopithecines became extinct at about 1 Million Years Ago because they were highly specialized in their diet
  • The Homo genus leading to modern humans appears at about 2.5 Million Years Ago


1. Kenyanthropus platyops

  • Maeve Leakey
  • Kenya
  • Encephalization – Increase in cranial capacity
  • From apes to austral. – Key feature is bipedalism
  • From austral to homo – Increase in cranial capacity (Encephalization) – approximately 2 Million Years Ago
  • Reduction in dentition
  • Contemporary of a. afarensis
  • Small braincase - Ape
  • Small molars - Human
  • Large, flat face – Ape


2. Australopithecus garhi

  • Bouri Ethiopia
  • Approx 2.5 Million Years Ago
  • Newest addition to Australo genus
  • 450 cc cranial capacity
  • Elongated lower limbs
  • Human like bipedalism


3. Australopithecus bahrelghazal

  • Brunet et al., 1995
  • Chad
  • Reduction of dentition
  • 3.4 - 3 Million Years Ago
  • Mandibular fragment
  • Similar to a. afarensis
  • First and only australopithecine found in North – Central Africa


4. Australopithecus sediba,

  • Approximately 1.8 Million Years Ago, Berger 2008, South Africa

Australopithecine traits -

  • Small brain (420 cc)
  • Long arms
  • Curved fingers

Homo traits -

  • Short fingers
  • Neural reorganization of brain (?)


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