The preserved remnants of once-living things.

Living primates evolved from fossil primates. 

We can understand what kinds of selective pressures led to the evolution of primates through fossils.

Only a small fraction of living things survive as fossils.

Paleos- (old)

-ontos (existence)

A field that is devoted to finding, studying, and understanding fossils.

I. Types of Fossils

II. Types of Fossilization

I. True fossils: petrified or hard remains of former animals and plants

Trace fossils: an imprint of, or a mark left by an organism

II. Preservation may occur in amber, ice, bog, cave, or tar

1. Death

2. Burial: organism preserved through sediment covering. Prevents decomposing.

3. Petrification/Mineralization: Minerals in groundwater or soil replace bone mineral, turning bone into stone.

4. Erosion will expose the older sediment with the fossils to the surface.

5. Discovery

Factors:

Skeletal remains must be buried quickly after death.

The remains must stay in an oxygen-free environment.

Layers of rock (strata) are laid down horizontal to the earth's surface.

All the deformations and re-arrangements of strata originate from earthquakes, volcanic eruptions, and human activity.

I. Principle of Superposition

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II. Principle of Cross-cutting Relationships

I. Older layers are laid down first and then covered by younger layers.

Older sediments are at the bottom.

II. Any geological feature that is cut is usually older than the thing cutting through it. (e.g. cake layers and candles)

I. Principle of Faunal Succession

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II. Index Fossils

I. Older, deeper layers contain older faunal (animals), and the successive, higher (younger) strata contain correspondingly younger animal remains. 

The deeper the strata, the older the fauna.

One type of fossil cannot reappear in higher layers (due to extinction).

II. Animal fossils that are resemblant of a given stratigraphic layer.

The categories of time into which Earth's history is divided by geologists and paleonotologists: eras, periods, epochs.

The earth is approximately 4.5 billion years old.

The scale is divided into two eons: the Precambrian and the Phanerozoic.

Precambrian: 4.5 to 543 million years ago

Phanerozoic: 543 million years ago to present

From oldest to youngest:

Paleozoic Era

Mesozoic Era (248-65 million years ago; "Age of Reptiles," but mammals arose around here)

Cenozoic Era (last 65 million years; main area of study)

Paleozoic: ---

Mesozoic: Triassic, Jurassic, and Cretaceous

Cenozoic: Tertiary Period and Quaternary Period

Tertiary Period consists of FIVE EPOCHS:

Paleocene (65-54.8 MYA)

Eocene (54.8-33.7 MYA)

Oligocene (33.7-23.8 MYA)

Miocene (23.8-5.3 MYA)

Pliocene (5.3-1.8 MYA)

Quaternary Period consists of THREE EPOCHS:

the end of the Pliocene

Pleistocene (1.8 million to 10,000 years ago)

Holocene (10,000 years ago to present)

Possible exam question:

I. How old is the Earth?

II. What epoch, period, era, and eon do we live in?

I. The Earth is 4.5 billion years old.

II. Humans live in Holocene Epoch of the Quaternary Period of the Cenozoic Era of the Phanerozoic Eon.

Phanerozoic Eon: Second half of Earth's age

Cenozoic Era: 65 MYA to present

Quaternary Period: 2.5 MYA to present

Holocene Epoch: 10,000 years ago to present

I. Lithiostratigraphy

II. Tephrostratigraphy

III. Biostratigraphy

I. The study of geological deposits and their formation, stratigraphic relationships, and relative time relationships based on their lithologic (rock) properties. The study of rocks.

II. Chemical components used to identify strata. Volcanic rocks' chemical fingerprint correlates across regions.

III. Uses faunal succession. Compares fossils from different stratigraphic sequences to estimate which layers are older and which layers are younger.

Measures the amount of chemicals that bones absorb from the soil.

The more chemical in the bone, the longer it has been buried.

Human skull found. Brain smaller than a neanderthal and a large mandible with ape-like teeth.

Believed to be the first European.

Exposed by fluorine analysis (relative dating techniques).

The mandible and skull fragment were shown to have different fluorine compositions.

Make use of geological or chemical processes that can be calibrated to a chronological scale if certain conditions are known.

Correlated to absolute chronology.

Location of magnetic north changes over time.

During rock formation, magnetic minerals in rock orient to magnetic north.

This polarity can be measured and does not change when magnetic north reverses.

Rocks have a polarity. These polarities can alternate over time.

GPTS shows how sequence polarities has changed.

Red bands on the magnetic time scale indicate reverse polarity; white bands indicate normal polarity.

Chronometric dating technique that uses radioactive decay of isotopes to estimate age.

Parent isotope - the original radioactive isotope the sample started with - is measured.

Daughter isotope - the isotope formed by radioactive decay of the parent isotope - is measured.

Daughter isotope + parent isotope = amount of total parent that existed before radioactive decay started.

The amount of daughter as a percentage of total parent tells you the number of half-lives expended.

Number of half-lives x Length of half-lives = Age Estimate

Uses the decay of isotope K (potassium) to Ar (argon).

Uses the ACCUMULATION of Argon from decay of Potassium.

Half-life of argon is 1.3 billion years - used to date very old things; useful for volcanic rock.

All argon gases are driven off by eruption of a volcano -> only potassium in rock; setting molecular clock to zero

LOSS of Carbon-14 since death of organism.

Only carbon-14 is radioactive; extra neutrons makes it unstable.

Half-life of about 5,730 years.

Plants absorb C-14 during photosynthesis; plant-eaters and eaters of plant-eaters get C-14 through plants!

Uses the decay of Carbon-14 to Nitrogen-14 in ONLY ORGANIC remains such as wood and bone to estimate the time since the death of the organism.

Origin of mammals during the Mesozoic Era (225-65 mya) - Era dominated by dinosaurs

Comet crashing into Earth contributed to extinction of dinosaurs and generated favorable, adaptive opportunities for mammals.

Plesiadapiforms

Anatomically more primitive than any living primate: small brain, prognathic face that projected in front of brain case, and small eye sockets on side, rather than front of face.

Also lacked postorbital bar: a bony ring encircling the lateral side of the eye, but not forming a complete cup around the eye globe.

Had diastema: gap between anterior teeth

Paleocene epoch was very warm

Flowering plants evolved

Insects increased in number; they pollinated plants and plants evolved visual cues for these insects

Plesiadapiforms ate these changing resources: insects and fruit from new plants

Two True Primates of the Eocene Epoch

Traits that defined them as true primates?

Adapoids 

Omomyoids

Slightly larger brains

Eye sockets positioned on front of face (stereoscopic vision)

Complete postorbital bar

Opposable big toe

Nails rather than claws 

Reduced snout (reduction in smell dependence)

Anapoids resemble...

Anapoids characteristics?

Modern Strepsirhines

Hence, these are the most primitive known group of primates.

Probably gave rise to strepsirhines.

Small to medium sized

Some sexual dimorphism

Arboreal

Quadrupeds active by day

Probably ate fruit and leaves

Long snouts

Most abundant in Old World

Omomyoids resemble...

Omomyoid characteristics?

Haplorhines

Diverged from the adapoids and may have given rise to the common ancestor of tarsiers and anthropoids

Smaller-bodied

No sexual dimorphism

Ate insects and fruits -> sharp teeth

Larger orbitals indicating nocturnality

Arboreal quadrupeds and leaping

More abundant in North America

Adapoids and omomyoids (i.e. early strepsirhines and haplorhines) divided up available food resources. 

Avoided competition.

Adapoids ate leaves and relied on smell.

Omomyoids ate fruits and insects; had shorter snout.

Higher primates appeared around 34 MYA, after the strepsirhine-haplorhine split.

Around 36 MYA, a cold snap called Grande Coupure resulted in large-scale extinction and replacement of many species: 

Temperature continued to decline: may have been caused by the movement of continents and changes in ocean  and wind currents.

First appeared 25-30 MYA.

Uncertain how monkeys got to South America, an island continent (Panama Isthmus was not yet formed).

Most scientists support Apidium-like ancestor that "rafted over" from Africa to South America.

Derived from Victoriapithecidae Uganda and Kenya 19 and 15 MYA

Victoriapithecus was one of the oldest and smallest anthropoid primates to shift to life on the ground.

2:1:2:3 dentition - 2 pre-molars

Low molar cusps and broad upper incisors probably ate hard fruits and seeds.

Cooling-drying period occurred again. From Antarctic ice sheet at the South pole.

Monkeys and apes diverged 25 MYA.

Hominoids nearly restricted to Africa.

Earliest Apes

Known as dental apes, based on the 5 rounded cusps of their Y-5 molars.

Dental apes were small bodied and more monkey-like in their skeleton.

Lacked suspensory shoulder for brachiating.

Walked on soles of feet, rather than knuckles.

Proconsul - lived in Africa 18-20 MYA. No tail, forward facing eyes, larger brain, smaller snout. Arboreal quadruped.

Morotopithecus bishopi - better candidate for last common ancestor of apes and humans. Possibly had short and stiff back and suspensory shoulder anatomy of modern brachiating apes. Inflexible lower spine.

Appeared 12-5 million years ago: larger-bodied hominoids diversified throughout Europe and Asia.

Ex: Pierolapithecus of Spain 12.5 MYA

Sivapithecus of India and Pakistan

Gigantopithecus in Asia; largest primate to ever live

Change in locomotion:

Apes: wide thorax for brachiating, no deep chests.

Monkeys: narrow thorax, but deep chests.

First distinctive evidence of apes is the dentition of dental apes (Y-5 molars), indicating a dietary shift to more fruits.

Monkeys: leaves

Apes: fruits