Human Evolution Final

Paleontology

Study of the history of life on earth as it is preserved in fossils

Archaeology

Study of humans in the past and present through the physical evidence of their behavior (including material culture)

Paleontology is

All life

Archaeology is

Human activity

Paleoanthropology

Study of human evolution through the fossil and archaeological records

Paleontological site

A location on the landscape where fossils are preserved

Archaeological site

A location on the landscape where the remains of past human activity are preserved

Why context is everything

Where or how something is found, need it to know age, meaning and relationships

Fossils

Preserved remains of plants and animals

Types of fossils

Body and trace

Taphonomy

Study of the process that affects the state of an organism’s remains from the time an organism dies until the time the fossil remains are recovered

Favorable conditions for preservation

Rapid burial, fine grained sediment

Unfavorable conditions for preservation

Weathering, consumption and trampling by animals, acidic soil, geologically active localities

Aeolian

Airborne

Lacustrine

Lake environments

Alluvium

River, stream

Colluvium

Hill

Karstic Systems

Landscapes formed by dissolving limestone

Caves and rock shelters

Protected environments formed in rock

Stratigraphy

Branch of geology that studies rock layers (strata) and their formation, composition, and relationships over time

Horizontality

Layers are deposited parallel to Earth’s surface

Superposition

Younger layers are deposited on top of older layers

Cross cutting relationships

Layer that cuts across others in younger than those it cuts

Lithostratigraphy

Uses the correlation of rock units to estimate the relative age of different areas

Tephrostratigraphy

Subset or type of lithostratigraphy that uses volcanic ash layers to match rock layers across different sites and determine their relative age

Biostratigraphy

Based upon the principle of faunal succession, there are predictable sequences of fauna through time, associated with particular strata

Paleomagnetism

Study of the Earth’s past magnetic field recorded in rocks, which helps date rock layers based on changes in magnetic direction over time

Potassium-Argon dating (40K-40A)

Measures the decay of potassium into argon in volcanic rock

Potassium-Argon dating materials

Glass, clay minerals, tephra

Radiocarbon (14C)

Measures the decay of carbon 14 to nitrogen 14 in once living things

Radiocarbon materials

Organic materials like wood, unfossilized bone, seeds, or shell

Potassium-Argon dating life

10,000 years ago to 4.5 billion years

Radiocarbon life

200 years to <50,000 years

Dendochronology

Study of tree ring patterns to determine the age of trees and calibrate radiocarbon dates

Uranium series

Measures the decay of uranium into other elements in calcium-bearing materials like cave formations

Uranium series life

Hundred to millions of years

Thermoluminescnce

Measures the last time a stone was exposed to high heat

Thermoluminescnce materials

Quartz, burnt stone tools, fired pottery

Thermoluminescnce life

100 to 1,000,000 years

Optically stimulated Luminescence

Measures the last time a grain of sand was exposed to sunlight

Optically stimulated Luminescence material

Single grains of sand (quartz), feldspar, pottery

Optically stimulated Luminescence life

1,000 to 400,000 years

Holocene

0.01-present

Pleistocene

2.6-0.01 Ma

Pliocene

5.3-2.6 Ma

Miocene

23.0 - 5.3 Ma

Oligocene

33.9-23.0 Ma

Eocene

55.8- 33.9 Ma

Paleocene

65.0-55.8 Ma

Rifting

Africa gets cooler and drier

Glaciation

Modern species go extinct

Platyrrhines + Catarrhines

Anthropoids

Epoch

Climate and tectonic activity

Pleistocence

Ice ages

Pilocene

Global cooling and drying, increasing aridity

Miocene

Global cooling and drying (LATE), expansion of grasslands Africa docks with Eurasia warm and wet (early-mid)

Oligocene

Latitude temp gradient, global cooling and drying, expansion of grassland and open woodland, D America and Australia detach from Antarctica

Eocene

Circumpolar currents establishes S America and Australia attached to Antartica. PETM (very warm)

Paleocene

Following dinosaur mass extinction

Hominids

Great Apes

Hominoids

African apes

Cercopithecoids

African monkeys

Catarrhines

African and Asian monkeys and apes

Platyrrhines

American monkeys

Anthropoids

All monkeys and apes

Bipedalism

Locomotion on two feet

Facultative bipedalism

Many animals practice it temporarily

Habitual bipedalism

Few animals practice

Obligate bipedalism

Modern humans are the only living primate that engages in striding, obligate bipedalism

Hypotheses to explain bipedalism

Postural feeding, Thermoregulation, Free hands for doing things, savanna, vigilance and threat, efficient energetics, terrestrial food gathering

Problem with postural feeding

Other terrestrially adapted primates retain quadrupedalism

Problem with thermoregulation

There are quadrupeds that occupy open areas with a lot of sun exposure

Problem with free hands

No evidence

Problem with savanna

Grassland began after earliest bipeds

Problem with vigilence and threat

Rare among chimpanzees

Problem with efficiency

No consensus

Problem with terrestrial food gathering

Also accessible by quadrupedal

Foramen magnum

Large hole at the base of the cranium, through which the spinal cord enters the skull

Short broad vertebrae

Supports the body’s weight during upright walking

Lumbar and s-curve

Acts as a shock absorber and helps center the torso over the pelvis, improving balance

Expanded tibial plateau and thicker neck

Provides a larger surface area to support body weight and absorb shock during upright walking

Femoral neck thicker, oblong it cross section

Resists bending and stress from supporting body weight on one led during walking

Expanded patellar surface

Stabilizes the patella (kneecap) and improved leverage for the quadriceps muscle during bipedal movement

Symmetry of the femoral condyles

Allows for smooth, even articulation at the knee joint, improving balance and reducing joint wear during bipedal gait

Bicondylar angle

Angle between the sagittal plane and the shaft of the femur

Valgus knee

The knee aligns underneath the hips as a result of the bicondylar angle

The foot

Shorter toes, robust big toe, non-opposable big toe, straight fixed metatarsals, complex arched foot, more robust calcaneus

Short, broad, bowl-shaped pelvis

Reorganization of the gluteal muscles, improves forward propulsion and stabilizes the hip

Short, broad, sagittally oriented iliac blades

Allow for improving positioning of the glueteal muscles, enabling greater balance, stability and lateral weight during bipedal walking

Lateral orientation of the glenoid fossa

Reduces range of motion for climbing, reflects decreased dependence on aboral locomotion

Shallow bicipital groove

Reduced leverage for powerful climbing, reflects decreased dependence on arboreal locomotion

Barrel shaped rib cage

Centralizes the body’s center of gravity

Humero femoral index

Longer legs for walking (Humerus length / femur length) x 100

Gracile, straight fingers

No need for hanging from the trees

Pilocene

5.3-2.6 Ma; hominin radiation

Miocene

23.0-5.3: Hominoid radiation

Trends toward bipedalism

Anterior foramen magnum, more compact feet with arches, robust and long leg bones, angled knees, bowl shaped pelvises

Names of probable hominins

Sahelanthropus tchadensis, Orrorin tugensis, Ardipithecus

Hard objects

Low and rounded, thick enamel

Tough objects

High and pointed, thick enamel