5a - Primate Evolution

Question 1

How are fossils formed

Answer 1

• When animals, plants, and other organisms die, they typically decay completely. But sometimes when the conditions are just right, they’re preserved as fossilsW

Question 2

What are fossils

Answer 2

Fossils are any remains of life preserved in rocks
- Bones, Teeth, Impressions, Footprints, Natural molds, termite nests, worm burrows, et

Question 3

Are fossils common

Answer 3

• Fossils are very rare: of all the life that has ever lived, we only find a very tiny percentage of it in the fossil record
• Due to their rarity, there are many gaps in our record of life in the past

Question 4

What needs to happen for us to find a fossil

Answer 4

Right conditions for preservation: slow decomposition, limit the access of bacteria and fungi

Fight conditions to be found: exposed at the surface somehow

An organism might get buried very quickly, ex seabed or stuck in sap

A body can get buried in an environment inhospitable to bacteria/fungi. Ex tar pit

Question 5

What are good fossil sites

Answer 5

Geological activity can expose buried fossils to the surface

Cave sites can accumulate high fossil concentrations

Question 6

What are bad fossil sites

Answer 6

Moist, high rate of decomposition, many bacteria/fungi/insects, very difficult to excavate

Question 7

What is Taphonomy

Answer 7

Goal: reconstruct the original community of plants and animals and its ecology

Taphonomy: the study of factors that affect organic remains prior to and during fossilization, and during excavation

Question 8

What Taphonomic factors impact what we see

Answer 8

Many taphonomic factors can impact what we actually see

• Predation, Accident, Disease, and Old age affect the transition from the Original Community of Plants and Animals to Organic remains
• Scavenging, Water transport, Trampling, Time averaging, Burial, Dissolution, and Mineralization affect the transition from Organic remains to Fossils
• Erosion, Collection and Preparation for study affect the transition from Fossils to Fossil Collections

Question 9

How can we date fossils

Answer 9

Relative Dating involves comparison to layers above and below

Absolute Dating products a numerical date and margin of error

Relies on knowing exactly where a fossil came from in the soil

• Its provenance

Question 10

What are the laws of stratigraphy

Answer 10

Laws of Superposition: Oldest on the bottom, youngest on the top

Principle of Cross-cutting Relationships: cutting strata are younger

Question 11

How can we absolutely date something

Answer 11

Determining a precise date for the age of an organic material by comparing the amount of naturally occurring radioactive isotopes of known decay rate

Radiocarbon dating:

Carbon exists naturally in two forms, C14 and C12

C14 decays at a known rate: half of it will be gone in 5730 years

Measure ratio of C14 and C12 in a fossil (less C14) compared to its normal ratio in the atmosphere = you can date how long ago it died by how much C14 has died by how much C14 has decayed

Question 12

When do primate fossils first appear

Answer 12

Major events in primate evolution and climate change occurred in the Cenozoic Era (65 mya to present) → when mammals first evolved

Question 13

Describe geologic time and how primates fit in

Answer 13

Divides earth’s history into time periods based on:

• fossils
• climatic changes

We can precisely date these time periods

Important Epochs for Primate Evolution:

Paleocene 66 mya

Eocene 56 mya

Oligocene 34 mya

Miocene 23-5 mya

Question 14

What were primates like in the Paleocene

Answer 14

In the Paleocene (~66-56 mya):

• Plesiadapiforms (rare) in Europe, Asia, and North America

Question 15

What were primates like in the Eocene

Answer 15

In the Eocene (56-34 mya):

• Omomyids appear in Europe, Asia, and North America
• Adapids appear in America
• Few fragments in Africa

Question 16

What were primates like in the Oligocene

Answer 16

In the Oligocene (34-23 mya):

• There are early Catarrhines from Fayum in Africa
• Almost nothing in North America
• Primates appear for the first time in South America

Question 17

What were primates like in Miocene

Answer 17

In the Miocene (23-5 mya):

• Prosimians, colobines (9mya) and early apes (22 mya) in Africa
• Colobines, early apes (16 my) in Europe and Asia
• Fossils - Early Platyrrhines? in South America

Question 18

What were primates like in the Pliocene

Answer 18

In the Pliocene (5-1.8 mya):

• Theropithecus and Early Hominins in Africa
• Cercopiths and Colobines in Europe and Asia.
• Platyrrhines in South America

Question 19

What were primates like in the Pleistocene

Answer 19

In the Pleistocene (1.8mya - 12 kya)

• Baboons and homo appear in Africa
• Carcopiths and Colobines disappear from Europe
• Cercopiths and Colobines present in Asia
• Platyrrhines in South America

Question 20

What were primates like in the holocene

Answer 20

Holocene (12 kya-Present)

• Essentially modern fauna

Question 21

Describe the Paleocene Epoch

Answer 21

66-56
Europe and North America at the time = subtropical forests

Primates probably evolved from a small, insectivorous mammal

Earliest primate-like mammals in the Paleocene:

Plesiadapiforms

Question 22

describe Plesiadapiforms

Answer 22

Plesiadapiforms

• some features similar to modern primates, some not seen in modern primates
• Extinct by end of Paleocene

Question 23

Describe the Eocene

Answer 23

56-34
Global warming and spread of tropical forests to northern Africa

First true primates appear and spread → adaptive radiation

• Adapidae: lemur-like
• Omomyidae: tarsier-like

Primate traits similar to Strepsorrhines:

• Forward Facing eyes
• Postorbital bar
• Reduced snout
• Vertical clinging and leaping
• Insectivorous and frugivorous diets

Question 24

Describe the oligocene

Answer 24

34-23
Climate is cooler, so the world is less forested

• Most primates disappear from northern climates and appear in equatorial regions

Earliest unambiguous Catarrhine fossils come from this time

• 32 mya in the Fayum Depression in Egypt

Sexual dimorphism

Ape like Y-5 molar pattern

Arboreal quadruped

Earliest fossil evidence of Platyrrhine monkeys appears as well

Question 25

describe the Miocene

Answer 25

The Miocene (23-5) was a time of ape adaptive radiations Extraordinary number of species and diversity Miocene deposits of Africa and Eurasia = Planet of the Apes

Question 26

Describe the early Miocene

Answer 26

Early Miocene 23-17 MYA Early Miocene in East Africa was forested - This is where we see the earliest probable ancestors of modern catarrhines: 23-17 mya - This is where we see the earliest evidence for ape like suspensory locomotion: 20 mya Early hominoids: 15 species of genus Pronconsul - Western Kenya - Ape like characteristics: no tail, large brain, Y5 molar pattern, fruit diet

Question 27

Describe the Middle Miocene

Answer 27

Middle Miocene 17-12 MYA The climate started to cool, and sea levels drop - land bridge to Eurasia opens Hominoid fossils from Germany, Spain, etc Time of major ape migration and dispersal into Eurasia e.g. Dryopithecus 13 MYA, France, Spain, Austria, Georgia - Dentition and brain size like modern chimpanzee - Arboreal and used suspensory locomotion

Question 28

Describe the Late Miocene

Answer 28

Late Miocene 12-5 MYA Climate has cooled and dried to the point that forests decline and open grasslands expand Hominoid fossils in Ethiopia, India, Pakistan, Vietnam, China, etc Apes start moving out of Europe into Asia, and back into Africa e.g. Sivapithecus 12-8 MYA, India, and Pakistan - Ancestor of modern orangutans - arboreal quadrupedalism and suspensory adaptations

Question 29

do we know the direct ancestors of living apes

Answer 29

Today, Thousands of Miocene Ape Fossils, But only 5 genera of Living Apes - Direct Ancestor still unknown Human and chimp lineage split about 7 million years ago.