1. The Record of the Past
Chapter 11

2. Fossils Fossils – Preserved traces of ancient organisms
To become a fossil:
- Remains must be suitable for fossilization
- Organism must be rapidly buried after death
- The material in which it is buried must be suitable for fossilization
Taphonomy - the study of how bones and other materials come to be buried in the earth and preserved as fossils

3. How Fossils Form
Mineralization - A form of fossilization in which the organic parts of an organism are replaced by minerals
Occurs very slowly as water carrying minerals, such as silica or iron, seeps into the tiny spaces within a bone
In some cases, the original minerals within the bone or tooth can be completely replaced
Traces of life forms that include insects trapped in tree sap, leaf imprints, footprints, skeletal remains and remains of digestive tracts
Requires either mud, silt, volcanic activity, etc.

4. Fossil Interpretation
The Fossil Record
Not a complete record of the history of living organisms on the face of the earth
Exhibits sampling error
Fossils information
Size, shape, and function of different muscles, the relative importance of the senses, and approximate brain size
Disease, injury, growth, and development
Artifacts – human made objects
Important clues to hominin behavior

5. Refining Taxonomy How we define a species Lumpers and Splitters
Reproductive success is a concept which is difficult to apply to the fossil record
Age, sex, and genetic differences all lead to variability in the fossil record
Lumpers and Splitters
Typologists (Splitters)
Viewpoint is that basic variation of type is imagined and that only fixed types are real
More likely to split two specimens that differ into two separate species
. Populationists (Lumpers)
Viewpoint is that only individuals have reality and that type is imagined
More likely to lump two specimens that differ into a single species

6. Taxonomy and the Fossil Record
Paleospecies
Defined in terms of morphology rather than reproductive success
Identified only by the fossil record
Chronospecies
An arbitrarily defined division in an evolutionary line
Identified by a relation of living descent

7. Geological Time Relative Dating
Provides information on which fossils in a sequence are older or younger
Based on stratigraphy
The principle of superposition states that the lower strata are older than those above
Layers of rock are referred to as strata
Index fossils are commonly found and have become markers for particular periods of time

8. Types of Relative Dating
Fluorine analysis - groundwater contains fluoride which, over time, is absorbed by bone
The rate of decay and the amount of dissolved minerals in the ground water varies from site to site
Biostratigraphic dating - particular areas of strata represent the same period of time as another through analysis of the fossils within
Paleomagnetism - used by studying the record of the Earth's magnetic field in rocks
Based on the following of the poles’ record of geomagnetic reversals

9. Chronometric (Absolute) Dating
Radiometric Dating - based on the decay of radioactive materials in a specific number of years known as the half-life
Carbon 14 dating - used to date organic material extending back to 75,000 years
C-14 has a half-life of 5,730 years
Potassium-argon dating – used to date materials in the 5-1 mya range
K-40, which has a half-life of 1250 million years, decays into Ar

11. Other Absolute Dating Techniques
Thermoluminescence - some materials collect energy and when subjected to high temperatures, give off light
Used as a means of dating ancient artifacts
Electron spin resonance (ESR) – used for dating material with unpaired electrons
Unpaired electrons absorb energy
Uranium series dating – Used to date objects like coral
Uranium decays to thorium
Amino acid racemization dating – measuring change in configuration of amino acids after an organisms death
Used to date once living tissue

12. The Geologic Time Scale
The evolution of life on earth has, over time, been impacted by the dynamics of the planet
Plate Tectonics
Shifting landmasses create new migratory routes and destroy others
Responsible for many alterations in climate
Geologists have divided the history of the earth into geographic divisions of time:
Eons, Eras, Periods, Epochs, and Ages
Most of the history of the planet is broken down into three major eras: the Paleozoic, the Mesozoic, and the Cenozoic

13. The Cenozoic The Cenozoic is known as the Age of Mammals
It is the time of the adaptive radiation of the mammals
The Cenozoic is divided into 7 epochs
Holocene begins ,000 years ago
Pleistocene begins million years ago
Pliocene begins million years ago
Miocene begins million years ago
Oligocene begins million years ago
Eocene begins million years ago
Paleocene begins million years ago
Anthropocene – a proposed epoch that would denote the period of earth’s history where human beings become the dominant influence on the environment