Continental drift
Movement over the surface of the globe of the immense plates of relatively light materials that make up the continents
Earth has changed over time
Climate change
Cooling and drying trend over the last 20 million years
Changing environment leads to
Adaptations
Changing environments led to
Selection pressures
How do scientists reconstruct ancient climates
-Reconstructing global temperature
Global climate change:
Cooling trend overall in last 65 million years
Warmer in early Eocene and early Miocene
Cooler and more variable in Pleistocene
Deep sea cores:
Oxygen isotopes
Different atomic mass (16 vs18)
O16 lighter - evaporates into snow and rain
- gets trapped in glaciers and poles during cold times
-high 18O/16O ratio during cold periods.
How do scientists know how old fossils are.
-fossilization
Most of what we know about organisms comes from fossils
Fossils- mineralized bones and teeth
Can reconstruct anatomical structure to answer questions
Environment has to be in right condition ( lakeshore or cave)
Needs to be buri es relatively quickly ( avoid scavenger)
Fossils are scarce
Carbon dating techniques
Isotopes Same element but different number of neutrons Can be radioactive Decay at a constant rate Half life Half life of carbon-14 is 5,730 years
Dating techniques: Clock in a Rock
Use other radio metric methods, carbon decays too rapidly
The decay of potassium to stable argon dating
- half life is 1.25 billion years
- volcanic rocks
- fossils not directly dated, dated to geological feature
- can date fossils millions of years old
- more recent technique :Ar-Ar dating
# more refined , can be done with single rock crystals
Uranium lead dating
Flowstones of caves
Other dating methods
Thermoluminescence
Electron- spin resonance
Paleomagnetic dating
Electron- spin resonance
Technique used to date fossil teeth by measuring the density of electrons trapped in apatite crystals in teeth
Thermoluminescence dating
Technique used to date crystalline materials by measuring the density of trapped electrons in crystal lattice
Bio stratigraphy
Uses the combination of other animal fossils found at a particular site to determine hoe old it is
Fossils are found in
commingled remains ( bits of teeth and bones)
What makes a primate a primate
Grasping hands and feet Nails instead of claws Forward facing eyes encased in bone Hand limb dominated locomotion Relatively large brain Generalized teeth 2-1-3-3 maximum formula
Climate change causes
Environment to change
Species will undergo micro evolution or macro evolution
Evolution of early primates
Plesiadapiforms
Plesiadapiforms: earliest primate fossil 54 to 65 mya in Wyoming, Montana, New Mexico, and Colorado They have: Grasping hands and feet Big toe Had a tail Eyes on the side of its head and low crowned molars Fruit not insects
Evolution of early primates
Eocene primates
Eocene primates: Adapids and Omomyids
During this time climate was shifting back and forth
Eocene 34-54 mya
Paleontologist found fossils that are unquestionably from primates
Earth warm and wet- tropical forests spread into N. America and Europe
Primates have evolved
Characters of Eocene primates: Adapids and Omomyids
Forward facing eyes Post orbital bar Short snouts Relatively large brains Nails instead of claws Hand limb dominated locomotion
Eocene/ Oligocene boundary
33-36 mya,
World was becoming slightly cooler and drier
Earliest haplorrhines can be found in
North Africa and China
Anthropoids are found in
Egypt
Oligopithecids
Old world monkeys and apes 2-1-2-3
Parapithecids
New world monkeys 2-1-3-3
Apes and old world monkeys diverged from
A common catarrhine ancestor
Miocene
5-23 mya
Warm and wet, became cool and dry over time
Apes versus monkeys
Apes have no tail Forelimb suspensions Short, stiff lower back Mobile joints Long arms and fingers All of these adaptations for locomotion leave their signature on the skeleton, and so are identifiable in the fossil records.
Morotopithecus
The earliest apes
Suspensory adaptations, or being able to hang from beneath a branch, is key hominoid feature.
First evidence in the fossil records for an ape that has adaptations for suspensory locomotion is Morotopithecus
Morotopithecus
Uganda 20 million years old Oldest ape? Face and teeth ape like Mobility at shoulders Stiff lower back Femur indicates slow climbing
Proconsul
Africa:17-23 mya Frugivorous Forest environment Ape like skull and teeth Monkey like postcrania ( neck down very different) Quadrupedal, non suspensory
Miocene ape evolution
Early and middle Miocene of Africa, apes diversified and flourished
Lots of fossil evidence
Skull and teeth ape like
Neck down, more like monkeys without tails.
Middle Miocene
10-15 mya
Apes had spread through out Eurasia ( Spain, France, Germany, Pakistan and Thailand)
Not found in Africa this time. Why.
Researchers haven’t found the Miocene apes fossils
Apes migrated to Eurasia due to ecological reasons
Earth became planet of the apes during
The Miocene
Late Miocene ape evolution
During the late Miocene 5-10 mya the climate continue to dry and cool
Apes that occupied the forest go extinct
Fossil record between 5 to 10 mya years ago is small
Genetic comparisons between humans, chimpanzees and gorillas indicate that the last common ancestor that we share with the African apes lived between 8 to 10 mya
After the gorilla linage branched, we continued to share a common ancestor with chimpanzees until about 5 to 7 mya
Thus , this is the key time for understanding what our shared ancestor with chimps and gorillas was like.
Understand how fossils form and how this skews our understanding of species timelines and relationships.
-Most fossils form when organisms die and are buried in sediment. Fossils are named (molds, casts, preserved remains, or petrified) based on the way they look and how they were formed.
Molds- are hollow spaces where an organism or part of the organism once was.
Casts -are copies of the shape of the organism that made the mold (ice cubes would be molds and trays are casts, for example).
Preserved remains -are organisms that are preserved in other substances (rock, sediment, ice, amber, etc.).
Petrified fossils -are fossils that have been soaked in water and turned to rock.
Scientists determine fossil age by using relative dating (what layer it is in in rock) or radioactive dating (finding the age based on the radioactive elements around the fossil and how much is left compared to the nonradioactive element).