Human Origins Pt 2

Generalized Characteristics of Primates

Forward rotation of eyes for binocular vision

Reduced Snout/Olfaction - sense of smell

Enclosed orbital plates

Vertical Trunk + Retention of Clavicle for Orthograde posture and shoulder mobility during brachiation

Retention of 2 unfused bones in lower arm allowing for forearm rotation

Prehensile (grasping) Hands: pentadactyl, opposble thumb, nails, and fleshy fingerpads

Encephalization: larger brain to body mass ratio

k-selection

Longer gestation

Learning flexibilty

Greater sociality

General Anthropoid characteristics

Larger body size

Larger brains

No moist rhinarium/reduced smell

Forward eyes/color vision

Fully enclosed eye orbit

Fused mandible at midline of the chin

Longer gestation and maturation

Increased parental care

More mutual grooming

Varied locomotion

Varied diets

Includes monkeys, apes, and humans

General hominoid characteristics

No tail and shortened trunk

Altered position and musculature of the shoulders

Greater cognitive ability

Behavioral complexity

Delayed maturation

Greater infant dependency

Highly k-selected

Includes apes and humans

General Strepsirhine characteristics

Greater olfaction - sense of smell

Rhinarium - moist hairless nasal pad

Reliance on scent marking

Diet of insects, fruit, leaves, and bark

Arboreal/terrestrial quadrupedalism

Leaping locomotion

Short gestation lengths and litters

Monogamy to larger social units

Includes Lemurs, lorises and Tarsiers (kinda they are very closesly related but are still considered haplorhines because of dry nose this might be a gotchya)

Encephalization

The evolutionary process of increase in complexity in the size of the brain relative to body size. Associated with higher cognitive capacity allowing for social behaviors and expansion of visual processes.

2.1.2.3. Dentition

Dentition of OW (Old World) monkeys apes and humans

2.1.3.3 Dentition

Dentition of NW (New World) monkeys

Enclosed orbital plates

Plates of the skull that separate the back of the eyes from the Temporalis chewing muscles. Found in all primates

The two major adaptive niches of primates

Arboreality - tree living

Sociality - chillin with the homies

Nocturnal vs Diurnal eyes

Nocturnal creatures have bigger eyes

Hominoidea

Superfamilly including all apes and humans

K-selection

energy and effort is put into raising young

R-selection

energy and effort is put into producing eggs and offspring w/ little rearing

Vertical clinging and leaping

Erect or vertical body position(orthograde)

Long, powerfully muscled hind limbs

Horizontal thrust away from trees

Broca’s and Wenicke’s areas

Areas in the brain’s left hemisphere responsible for language development

Socioecology

The relationship between organismal behavior and their environment

Socioecology variables

Food types - Caloric value and net value after acquiring

Food & water distribution - scattered vs clumped and seasonal availability

Distribution and types of predators

Distribution of non-predator competitors

Distribution of shelter/sleeping sites

Sexual dimorphism

External differences between the sexes of a species other than that of sexual organs

Sociobiology

The relationship between an organisms social behaviors and their biology. The evolution of behavior via natural selection

Inclusive fitness (kin-selection)

Explanation of altruistic behavior within the framework of Darwinian selection. Altruistic traits can increase in frequency within a species based on the relatedness of the members of the species and the how disadvantageous the behavior may be and how advantageous it may be on the recipient.

Altruism

Behavior that benefits another individual at some potential risk or cost to oneself

Group selection

Evolutionary theory where natural selection acts on whole group so f organisms rather than that of individuals, favoring traits that benefit group survival such as altruism or cooperation.

Human Social structures

Mutlilevel, nested alliance structures

Families formed by conjugal (marriage) partners

Monogamy common

Flexibility - either sex can disperse from groups

Brother-sister bonds maintained throughout life

Bilineal kin recognition (recognition of both mother and fathers relatives)

Affinal bonds (in-law relationships)

Non-human primate social structure

Independent, single group entitites

Lack of conjugal partners

Monogamy virtually non-existent

Single-sex dispersal pattern

Brother-sister bonds not maintained

Matrilineal kin recognition

No structured affinal relationships

Plate tectonics

The concept of shifting continental plates in earths crust that subduct beneath each other and spread out due to convention in the earths mantle. Proposed and developed by Marie Tharp (oceanographic cartographer) and Alfred Wegener (Meteorologist)

Continental Drift

The concept of continental landmasses rearranging due to plate tectonics (pangea type shit)

Pangea

That time earth was one big continent (200 million years ago)

Laurasia & Gondwana

That time Earth was two big continents (180 million years ago)

Laurasia was the northern continent

Gondwana was the southern continent

First appearance of primates in the fossil record

The earliest definite primate appears in the Eocene epoch of the Cenozoic era about 54 mya

Geologic Epochs

Division of time within the cenozoic era (era after the K/T extinction)

From oldest to youngest

Paleocene

Eocene

Oligocene

Miocene

Pliocene

Pleistocene

Holocene

Sivapithecus

The likely ancestor to extant Asian apes like Orangutan & Gigantopithecus

Found in Asia

~ 12.5 - 10.5 mya

Gigantopithecus

Largest known ape to exist

Closely relatied to sivapithecus and likely the sister ancestor to Orangutans

Known from jaw elements and isolated tooth

Good representation of diversity among hominoids

Perhaps overlapped in environment with homo-erectus

Found in Asia

300,000 - 200,000 years ago

Preconsul

Possibly one of the first ape-like primates

Had ape-like cranial and dental traits

lacked tail like apes

Had a long torso and limb features similar to monkeys

Found in Africa

21-17 mya

Dryopithecus

similar to modern apes but highly arboreal

Shares the y-5 molar pattern that appears in apes and humans

Found in Europe

12-10 mya

Miocene Hominoid Characteristics

Increasingly ape-like dental structures and brain size

Loss of tail

y-5 molar pattern

Large canines

Large incisors

Variable molar

Suspensory quadrupedal locomotion

However still have longer torso and limb features similar to monkeys

Y-5 Molar pattern

A pattern present on the first molar that splits the cusp using a y-shape present in apes and humans. Hominoid trait.

Canine sectorial complex

The dental pattern that allows for a gap in the between the canines in the lower jaw that will house the upper canine. This gap is called a diastema. Trait of miocene hominoids and Early hominins

Absolute dating methods

Using radio-isotope decay and half life ratios from rock samples to discern an exact date rage

Includes:

Potassium-Argon

Argon40-Argon39

Carbon14

Relative dating methods

Using the known dating of faunal and floral found within the same stratigraphic layer or adjacent ones to obtain a rough estimate on the geographic date of fossils.

Taphonomy

Study of how bones and other materials come to be buried and preserved as fossils

Processes of sedimentation

Actrion of streams and soil movements

Preservation properties of bone

Carnivore disturbance factors

S. African caves and carnivore behavior

An explanation for a high concentration of hominin fossils in caves using carnivore disturbance factors

Theory is that leopard like felines would hunt and consume hominins within trees and then drop corpses into cave systems created by dissolving rainwater.

Biostratigraphy (faunal correlation)

Using fossil assemblages of animals to date, correlate and characterize rock layers.

Palynology

Study of mircoorganisms and microscopic fragments within stratigraphic layers that aid the reconstruction of past environments and assists with geologic dating.

fauna that help date early hominins

Pigs/Suids

Rodents

Horses/Equids

Mammoths/Mammuthus

Characteristics of early hominins

Larger brain than miocene hominoids yet still ape-like

Bipedal & retention of climbing ability

reduced sectorial complex

Tool use (later hominins begin tool use starting 3.3 mya but become more common 2.6 mya)

Foramen magnum position

The site where the spinal column connects with the skull

Backwardly (posteriorly) placed in non-biped

More forwardly (anteriorly) placed in biped

Spinal curbature

Change in spinal curvature to better handle vertical load bearing

non-bipeds - little curvature

bipeds - curvature in 3 alternating curves

Iliac flaring and orientation

Alteration in the pelvic structure allows for better bipedal movement with narrower hips and increased capacity of gluteal muscles to assist in walking.

Gluteal abductors

The development of gluteal abductors allows bipeds to avoid using body weight swing while walking as abductors maintain the balance of the pelvic bowl.

Pelvic tilt/listing

The sway of the pelvis in non-bipeds that attempt temporary bipedalism in order to facilitate weight transfer between support legs

Femur bicondylar angle

The inward angle of the femur, keeping legs more beneath the body for vertical structure support. Present in bipeds

Large calcaneus (heel) bone in foot

Assists in shock absorption with walking and acts as landing points for feet. Helps with rolling steps. Present in bipeds

Thermal regulation scenario for bipedalism

Bipedalism as an advantage for thermoregulation by reducing surface area for solar radiation and increasing surface are for wind removal of sweat.

Earliest evidence of bipedalism

~7 mya Sahelanthrpus tchadensis in central africa

Exaptation

A trait which evolved a specifric environment by chance then confers an adaptive benefit to a species in another newly occupied environment

Sahelanthropus tchadensis

Pre-Australopith

6-7 mya

Discovered by Michel Brunet

Found in North Central Africa

Large brow ridge - thicker than gorillas

hominin features:

Relatively small canines

Lack of sectorial complex

Intermediate molar enamel thickness

Reduced facial size and projection

Well developed browridge

Ape derived features:

Small brain

Intermediate features:

Foramen magnum

Orrorin tugensis

Pre-Australopith

~6 mya

Described by Andrew Hill and Brigitte Senut

Found in East Africa

Femur shows clear evidence for bipedalism

Ardipithecus ramidus

Pre-Australopith

5.8-4.4 mya

Discovered by Tim White

Found in rift valley (East Africa)

Small brained

Diet similar to chimpanzees based off of teeth

Bipedality is debated (probable arboreal quadruped)

Still had opposable toe

Possible example of exaptation

Australopithecus anamensis

4.2-3.8 mya

Found initially by Bryan Patterson, later contributions form Meave Leakey and Alan Walker

Found in East Africa

parallel tooth row

Rounded palate shape

Raymond Dart

Discoverer of the Taung Child the first early hominin found in Africa and the first discovery of a human genus different than our own

Australopithecus Afarensis

3.6-3.0 mya

Discovered by Mary Leakey

Found in East Africa

Small brain

Longer upper limbs

Flat forehead

Sorta large molars

Less pronounced brow ridge

Australopithecus africanus

3.3-2 mya

Discovered by Raymond Dart

Found in South Africa

Smaller canines

Shorter face

More pronounced brow ridge

Larger cranial capacity

Quite large molars

Found in Sterkfontein cave

Paranthropus robustus

2-1.5 mya

Found in South Africa

Found by Robert Broom

Found in Swartkrans cave

Premolars nearly as large as molars (molarization

Large mandibles

Non-parallel tooth rows

John Robinson

Student of Robert Broom who developed the distinction between robust (Paranthropus) and gracile (Austrapithecus) Australopithecenes

Louis Leakey

Discoverer of Zinjanthropus (Paranthropus) boisei in Olvudai Gorge

Paranthropus boisei

2-1 mya

Discovered by Louis Leaky

Discovered in East Africa

High molarization

Reduced canines and incisors

Heavy wear on first molars

Obvious sagittal crest

Prevelant zygomatic Arch

High level of sexual dimorphism

Paranthropus aethiopicus

2.5 mya

Found by Don Johanson

Found in East Africa

Laetoli Foot prints

Foot prints left by A. afarensis 3.6 mya

Australopithecus sebida

Dated 1.78 - 1.95 mya

Newest species of hominin found

Found in south Africa

Found by Lee Rogers Berger’s son Matthew Berger

Australopith Height average

4 ft

Australopith Sexual dimorphism

High level of sexual dimorphism

More present in Gracile forms (Australopithecus) than Robust (Paranthropus)

Swartkrans Cave

Cave sight in Southern Africa where many Paranthropus robustus were found

Gracile Australopithecenes

Australopithecus

Reduced premolars and relatively normal incisors

Assumed to be more omnivorous and higher level of aggressive behavior

Robust Australopithecenes

Paranthropus

More molarized premolars and smaller incisors

Assumed to be more peaceful vegetarians

Taung Child

A. africanus

discovered by Raymond dart

Though it had a small brain size it showed clear evidence of bipedal behavior due to Foramen magnum position and dental development

Zinjanthropus boisei

Discovered by Louis Leakey

Original name for Paranthropus boisei