Bones W7
February 21st
Geology
What is geology and why do we care?
-Study of the earth
-Study of rocks
-Study of land formation
-The science that deals with the dynamics and physical history of the earth, the rocks of which it is composed,
and the physical, chemical and biological changes that the earth has undergone or is undergoing
-Enables us to put fossils in context
Geologic Time in Perspective
-January 1 (15 billion years ago)
-Big Bang
-May 1 (12 billion years ago)
-Galaxies Form
-September 4 (5 billion years ago)
-Our Solar System Forms
-September 12 (4.5 billion years ago)
-Earth Forms
-October 4 (3.6 billion years ago)
-First fossils, photosynthesis?
-November 13 (2 billion years ago)
-Complex single celled organism
-November 19 (1.8 billion years ago)
-Free Oxygen
-November 21 (1.7 billion years ago)
-Multicellular organisms
-December 8 (1 billion years ago)
-Sexual Reproduction
-December 18 (590 million years ago)
-Algae, worms, crawlers
-December 19 (510 million years ago)
-First vertebrates
-December 22 (438-360 million years ago)
-Fish, Land Plants, and Amphibians appear
-December 26 (245 million years ago)
-Reptiles and Mammal-Like Reptiles appear
-December 26 (220 Ma)
-First mammals appear
-December 31 (40 Ma-500 years ago)
-First monkeys (40 Ma) 1:00 am
-First apes (23 Ma) 11:00 am
-First hominids (5.8 Ma) 9:00 pm
-First stone tools (2.57 Ma) 10:30 pm
-Cave paintings (30 Ka) 11:59 pm
-Farming (12 Ka) 11:59:35 pm
-Renaissance (500 years) 11:59:50 pm
Scale:
1 day = 42 million years
1 hour = 1.75 million years ago
1 minute = 30,000 years
Paleozoic Era (543-252 MA)
- ‘Old Life’
-Most modern phyla evolved
Mesozoic Era (251-65 MA)
- ‘Middle Life’
- ‘Age of Reptiles’
-First mammals appeared
-Cenozoic Era (65 MA-present)
- ‘New Life’
Within Cenozoic time is split between two periods
PRESENT
-Quaternary
-Holocene (10,000)
-Pleistocene (2.5 MA)
-Tertiary
-Pliocene (5 MA)
-Miocene (23 MA)
-Oligocene (34 MA)
-Eocene (56 MA)
-Paleocene (65 MA)
PAST
How to Make a Fossil
-Phase 1: Death
-How an animal dies determines much of its future as a possible fossil
-Phase 2: Burial
-Purposeful or Accident
-Phase 3: Replace calcium with minerals
-Does not happen in amber (soft tissue is still even preserved)
-Phase 4: Exposure
-Erosion
-Usually combined with tectonic activity
Biases of Fossilization
-Can favor certain body parts, often durable or hard ones, i.e., jaws, teeth
-Can favor certain types or sizes of animals i.e., corals, large-bodied mammals
-Cultural processes: burial of certain types of humans, i.e., infants or juveniles
-Biological processes: age or sex-biased diseases or predators that kill certain types of individuals
Taphonomy
-What happens to individuals after death? (taphos = death GR.)
Questions a taphonomist might ask:
-Did scavengers modify this fossil assemblage?
-What bones do (modern) scavengers eat, what bones do they leave behind?
-Did the animal die where it lays, or was it dragged?
Geologic Principles
Law of Original Horizontality
-Layers of sediment are originally deposited horizontally under the action of gravity
Law of Superposition
-In any undisturbed sequence of rocks deposited in layers, the youngest layer is on top and the oldest is on the
bottom, each layer being younger than the one beneath it and older than the one above it
Uniformitarianism
-The same natural laws and processes that operate in the universe now, have always operated in the universe
-Type of deposition
-Tectonism
-Volcanism
-Erosion
Fluvial—River Deposits
-River systems
-Water Energy
-High energy deposits and pebble sediments
-Low energy deposits smaller sands
-Really low energy, silts
-Animal Fossils
-Trapped in floods
-Killed near the river
-Overbank flood deposits
Overbank Flood Deposits
-When sediments are deposited in flood plains
What Fluvial deposits look like in the fossil record?
-Kind of a mess
-Particle size matters
-They can tell two fast a river was moving, and which way it was moving
Lacustrine—Lake Deposits
-Lake Systems
-Low Level Energy
-Silts
-Clays
-Animals
-Some float from the fluvial system
-Killed near the lake
-Hippos, crocodiles, and fish
What Lacustrine deposits look like in the fossil record?
-Nice, even
-Killed near a lake
-Easy to distinguish
Volcanic
-Volcanic Systems
-Ash
-Lava—Basalt Flows
-Animals
-Trapped in the ash
-Trapped underground
-Footprints
What do volcanic deposits look like?
-Particle sizes are small
-Quite a thick layer
Cave Deposits
-Cave Systems
-Chambers are filled with sediments and biota (living things)
-Animals
-Live there
-Washed in
-Fall in
-Dragged in
Geologic Dating Methods
-How do we know that “Lucy” lived around 3.1 MYA?
-Two Basic Types of Dating Techniques
Absolute: This fossil is 3.1 =- 0.4 MYA
-EX: Potassium Argon Dating
-Radio Carbon Dating
-Paleomagnetism
Relative: this fossil is younger than that fossil
-EX: Faunal Correlation
-Superposition
Absolute Dating: The basics
-Over time, radioactive isotopes (parent) change into stable isotopes (daughter)
-Geochronologists know various rates of isotopic decay
-Change is constant and can be expressed as a half-life: the time it takes to reduce a parent atoms in the
material by 50%
Absolute Dating: Potassium-Argon Dating
-Volcanic ash has crystals of feldspar that contain potassium
-When a volcano erupts, it resets the Potassium (K40) to 100%
-Figure out the date of the rocks above/below the fossil, not the fossil itself
-Volcanic Layer = Tuf
What happens when no tuff?
Absolute Dating: Radiocarbon Dating
-Living species have a constant amount of C14 (R0) due to constant amount in atmosphere
-After death, they slowly lose C14 due to radioactive decay of C14 into C12
-Compare ratio of C14/C12 (Rm) in dead tissue to amount of C14 in atmosphere (R0)
-Calibrate this ratio against known scale of time
-Very reliable to 10,000y
-Fairly reliable to 40,000y
-Sometimes up to 70,000y
-Archaeological applications
Absolute Dating: Paleomagnetism
-The earth’s magnetic polarity switches every few hundred thousand years. Iron particles in rocks track this
switch.
Relative Dating: Faunal Correlation
-Some lineages of animals leave behind a good fossil record scattered over a wide area
-East Africa
-Pig 1 (4.0-3.2 Ma)
-Pig 2 (3.6-2.95 Ma)
-Pig 3 (3.4-3.0 Ma)
South Africa
-Pig 3
South African site is 3.4-3.0 Ma
February 23rd
Tales of climate’s influence on primate evolution
NEED TO KNOW ABOUT THE CENOZOIC ERA
Cenozoic Era:
-Overall cooling (with fluctuations)
-Changing temperatures caused by plate tectonics
What was life like on earth during the Paleocene (65 million years ago)
-Angiosperms (flowering plants) had just gone through a big adaptive radiation
-Flowering plants: Nectar attracts animals that inadvertently carry pollen to other plants
-Evolved new, large fruit types: Animals eat them and inadvertently spread seeds
-They became a dominant tree species 100-60 MA (million years ago) and they replaced gymnosperms
Pre-Angiosperm Forest
-Dominated by non-flowering trees (Gymnosperms)
-Hot
-Generally open
-Not particularly complex
-Dominant Animals: Reptiles
Angiosperm Forest
-Lush, many layers
-Closed
-Cooler
-Many niches
-Dominant Animals: Mammals and Birds
Angiosperm Hypothesis of Primate Origins
-The availability of abundant fruits and flowers in the terminal branches of tropical forest trees provided a
windfall of foods (fruit and insects) that were utilized by the earliest primate ancestors because of the
adaptations that all primates have today
-Forward facing eyes, terminal branches, eating insects
Plesiadapiforms
-Early Paleocene
-Diverse group of primate like animals
-Earliest primates? Some similar traits to later primates
-grasping hands, molars, nail on big toe
-Also lack many critical primate traits
-Found across North America and Europe
Reconstruction of Plesiadapis
-Eyes on the side of head
-Long snout
-Claws, not nails
-No post-orbital bar
Experts have concluded that they aren’t really ancestors of the first primates, they think that the
plesiadapiforms were more of a sister taxon that has gone extinct
Eocene
-Suddenly a ton more groups popping up
-Primates are undergoing big adaptive radiation
-Adaptive Radiation: the evolution of an ancestral species, which was adapted to a particular way of
life, into many diverse species, each adapted to a diferent ecological niche
Eocene Global Climate Change
-Most extreme change in climate happened at the beginning of the Eocene, which was a big spike in temp
-Many terrestrial mammals went extinct, but numerous modern mammalian orders engaged
-Caused ocean temps. to increase
-Opened other niches for animals to evolve
Environmental Factors in the beginning of the Eocene
-Northern latitudes had tropical climates
-Tropical climates caused rain forests north to present-day Alaska
Big Horn Basin now
-Dry, cold, super-hot bed for Eocene mammal fossils
55.8 Million years ago, was a tropical forest filled with swamps, big mammals, hot, etc.
25,000 years later…
-Modern looking primates exploding all over north America
The First Modern Primates
-Northern Latitudes
-Having northern latitudes provided more opportunity for primates to migrate across the continents
Characteristics of Eocene Primates
-Postorbital bar in skull (all primates)
-nails
-Opposable thumbs and big toes
-Shorter snouts that other mammals
-2.1.3.3 dental formula
-Convergent orbits
-Binocular vision
Two Major Groups (Africa
-Adapoidea
-Diurnal
-Generalized arboreal quadrupeds with some leaping
-Resembled lemurs
-Omomyoidea
-Insectivorous
-Nocturnal
-Leapers
-Resembled tarsiers
in Asia, Eosimiidae
-tiny (less than 10 grams) primates
-Possibly ancestors of Haplorrhini
-2 species ~10 grams
Climate Change from Eocene to Oligocene
-Surface sea water much cooler
-Antarctic ice cap developed
-Northern-most tropical forests disappeared
Latest Eocene—Earliest Oligocene
-Primates mostly in CHECK SLIDES
Oligocene
The Fayum, Egypt
-Outside of Cairo
Haplorrhine (ancestors of monkeys and apes) in Egypt
-Earliest unambiguous Haplorrhines in Oligocene
-Three families
-One family had: Reduction of snout, no grooming claw, post-orbital closure, 2.1.3.3 dental formula,
fetal mandibular closure
-Other two families
-Had the above PLUS: 2.1.2.3 dental formula
Aegyptopithecus
-One of the earliest Catarrhines (old world monkey today)
-Pre-dated split between the OWMs and Apes
-Characteristics
-2.1.2.3 dental formula
-Generalized molars
-Raccoon sized
-Climber
AND THEN PRIMATES GOT TO SOUTH AMERICA
1. Evolved right there is S. America: Probably not. No pre-Eocene primate like fossils in S. America
2. Rafted from North America: Probably not. Ocean Currents- North America>Europe and Africa> South
America
3. Rafted from Africa—A Fayum ancestor with a 2.1.3.3 dental formula: Likely! Caviomorph rodents appear in
S. America at about the same time with African roots
All the living Platyrrhines are descendants of this dispersal event!
New World Primates: Oligocene>Pleistocene
Miocene
Climate Change Again
-Warming at end of Oligocene
-Northern tropical forests
-But then cooling/drying mid-Miocene
-Seasonal forests, tropical woodlands
-Land bridges (Antarctic ice cap)
Miocene Fossil Ape Localities
-Lots in Europe, Asia, and Africa
Proconsul Species
-Genus found in about 6 localitites
-Ranges from 20 my to 17 mya
-Several species known
-Tail or no tail?
-Y-5 molar pattern (like apes)
-Largish brain
-Flexible shoulder
Dryopithecus
-West-Central Europe
-Short vertebral column
-Broad chest, long arms
-Powerful hands
Oreopithecus- A Bipedal Ape
-Late Miocene (8 mya)
-Found in Tuscany
-Long arms, short legs
-Short trunk
-Flexible shoulder
-Inner ear bony labyrinth shows configuration of bipedalism: large circles suggest sensory control of
locomotion
-Foot shows unique adaptation for stability on two feet: a very widely displaced big toe for walking
Sivapithecus
-Found in south Asia
-Three diferent species ascribed to genus Sivapithecus
-First appear around 13mya
-Disappear around ~5-8mya
What about Africa?
-Gap in the fossil record
-15-8 MA
-Presuming there were lots of apes, but nothing is known forsure
Darwin Argued for an African origin of Humans
-Humans evolved from African apes
-Molecular phylogenies indicate that the divergence hominins from African LOOK ONLINE FOR SLIDES
