lecture 8 Flashcards
There are three general phases to paleoanthropological research:
discovery
description
classification
what is discovery
of a fossil specimen via a predictive model, and the conservation of the find
what is description
that permits comparison with other fossil discoveries
what is classification
and the establishing of evolutionary relationships with previously-‐ discovered fossils
what is Fossilization
is the environmental or chemical alteration of the physical structure of an organism’s remains, which generally keep their original form.
is fossilization common
It is a very rare process, and is almost always limited to hard, durable parts of the body: bone, shell, teeth, etc.
what is the best preserved, typically
teeth are always the best preserved because of the enamel, and you can get so much DNA from it
Two general conditions must be met for fossilization to occur:
rapid burial
limited exposure
what is rapid burial
of the specimen and steady accumulation of soil over time (no erosion).
what is limited exposure
to oxygen, heat or animal scavenging/burrowing
The study of natural processes that lead to fossilization is called what
taphonomy
true or false
The same taphonomic forces that favor fossilization generally hinder discovery of new fossils
true
what is A predictive model
is used in the research design that will evaluate the likelihood of finding fossils in a given location
Most primate fossils have been discovered in one of three general location types:
volcanic deposits and rift valleys
river or lake deposits
(as they expand and contract, there is constant movement of soil)
sheltered cave systems
After discovery, the specimen must be described and classified as one of 2 things;
A member of a previously identified species
or
Representative of previously unknown species or genus
In making these determinations, the researcher must take into account:
1) the physical (morphological) variation of individuals within a species
2) pathological anomalies (diseases)
There are two general ways in which fossil specimens can be classified:
Phenetic classification
Phylogenetic (or cladistic) classification
what is Phenetic classification,
which is based solely on the similarities of physical traits, such as size, color, general morphology
what is Phylogenetic (or cladistic) classification,
which organizes organisms according to their evolutionary descent
Phenetic Classifications…
…can be mislead by:
Convergent (parallel) evolution
what is Convergent (parallel) evolution
the evolution of traits that are similar in function, but evolved from different structures (aka analogous traits)
what are analogous traits.
Similar structure between the wings of bats and birds, but different evolutionary trajectories
Cladistic Classifications…
… try to express evolutionary relationships between species based on what
homologous traits, traits are similar because of ancestry.
what is a clade
Clade = a group of species that share a set of derived homologous characteristics
Homologous Characters (Traits) can be what
Can either be primitive (ancestral) or derived
what is an ancestral trait
The presence of 5 fingers and toes in primates is an ancestral trait.
ancestral is shared
what is a derived trait
The alignment / structure of the human big toe is a derived trait
derived is different
There are two general means of estimating the age of archaeological and paleontological specimens:
Absolute vs. Relative Dating
what is Relative dating,
which tells us the order in which events occurred, but little else
what is Absolute dating
provides an age estimate in calendar years
what does Stratigraphy do
Form the basis for relative dating
what are the principles of Stratigraphy
the Principle of Original Horizontality,
what is Principle of Original Horizontality
which holds that strata were originally laid down horizontally, and any alterations are the result of later processes
what is 2) the Principle of Superposition,
which holds that older deposits among strata are lower than younger deposits
what is 3) The Principle of Cross-Cutting Relationships
states that a geological feature must exist prior to a feature cutting across or into it.
what is 4) The Principle of Faunal Succession
states that fauna appear in predictable sequences in strata. Relies on the concept of an index fossil
Relative dating techniques are derived from the geological principle of what
uniformitarianism and the principles of stratigraphy
Relative dating techniques are derived from the geological principle of uniformitarianism and the principles of stratigraphy, and form two postulates:
1) the Principle of Superposition
2) “comparison by fossil,”
what is “comparison by fossil,”
which assumes two widely-‐separated strata with similar minerals, fossils or artifacts are contemporaneous (biostratigraphy)
chichis more reliable, absolute to relative dating and why
Absolute dating is much more reliable than relative dating, as it provides chronological age estimates, always with an error range.
All but a few of the most commonly used absolute dating techniques are what
radiometric
what is radiometric
that is, they rely on radioactive phenomena, specifically, the measurement of radioactive decay.
isotopes can be radioactive (decay) and others can be stable… this helps us determine the time of the fossil
what are the types of absolute dating
Carbon-14 (Radiocarbon) Dating Potassium-Argon (K-Ar) Dating Argon-Argon (Ar-Ar) Dating Thermoluminescence Electron Spin Resonance (ESR) Amino Acid Racemization
what is Carbon—14 testing
measures the decay of 14C, which is an unstable radioactive isotope of carbon–the key element in all living things
Carbon-14 testing is based on the premise that 14C breaks down at a consistent rate; every 5,730 years, its concentration within a sample is halved; this is referred to as its half-life.
When an organism dies, it has equal parts carbon-14, which decays, and carbon-12, which does not. By measuring the ratio of 14C to 12C, we can see how much time has passed since an organism died
what is a limitation of Carbon—14 testing
It can only be used to date carbon— containing organic materials (e.g., bone, wood and other vegetation, etc.).
only done on things made up of carbon
what range does Carbon–14 testing cover
Its effective range of dating is between 300 years BP and 50,000 years BP
what is BP
(BP— before present… 1950 is the arbitrarily set “present”)
what is Potassium-Argon (K-Ar) Dating
Radioactive Potassium-40 breaks down into Argon-40 gas very slowly. The transformation half-life is 1.3 billion years! We measure the ratio of Argon- ‐40 to nonradioactive Potassium-39, which doesn’t transform or break down; the differences represent the age of the sample.
what is K-‐Ar dating is used for
to date potassium-rich volcanic rock and ash
what is the date race for K-‐Ar dating
Because of Potassium-40’s long half-life, the upper age limit of K-Ar dating is effectively unlimited; the lower limit, however, is around 500,000 years BP
what is Argon-Argon (Ar-Ar) Dating
Argon-Argon dating is similar in principle (and date limits) to K-Ar dating, only instead of measuring the amount of Potassium-39 (which is found in minerals as a solid), then measuring the amount of Argon-40 (which is found in minerals as a gas) and comparing the ratio, it first converts non-radioactive Potassium-39 into radioactive Argon-39 and then compares the ratio of Argon-40 to Argon-39.
is Argon-Argon (Ar-Ar) Dating very reliable
This technique is considered more reliable than K-Ar dating, as it requires only one sample for testing, and is testing only one variety of element (Argon).
what is a limitation for Argon-Argon (Ar-Ar) Dating
where as in K-Ar there are two samples needed from the same thing and error can occur when taking one+ sample
what is Thermoluminescence
measures the light emitted by electrons trapped in the lattice structure of some crystalline minerals
how does Thermoluminescence work
Electrons become trapped in the crystal structure due to background radiation; the accumulation of electrons occurs at a fairly steady rate.
The electrons are freed by heat; each time a sample is heated, the “electron clock” is reset to zero
can measure the last time it was heated and that exposure to heat is the point in tie we want to know about … it releases e- when heated then absorbs more e- from the atmosphere effectively “resetting” the e- clock
what is Thermoluminescence used for
this is used especially with pottery
what is Electron Spin Resonance (ESR)
ESR operates on the same principle as thermoluminescence, only instead of releasing the trapped electrons, the magnetic field of the sample is measured to determine how many electron “traps” exist in the lattice
what is the date range for Electron Spin Resonance (ESR)
The effective dating range is anywhere from 3,000 years to 300,000 years.
what can Electron Spin Resonance (ESR) be used on
It can be used on cave deposits, fossil shells, corals and tooth enamel
what is Amino Acid Racemization
Amino acid racemization measures the transformation of amino acids from one form (L) (when they are alive) to another form (D) after death of the organism. This transformation process is called racemization.
what can Amino Acid Racemization be used for
The ratio of D to L amino acids increases over time, and can be measured to provide a date of death
what is included in Earliest Primates
Earliest prosimians (the Strepsirrhines and tarsiers)
Earliest Haplorrhine monkeys (both Old World and New)
Earliest Haplorrhine apes (aka, hominoids)
One thing we must remember is that our fossil knowledge of early primates is very limited, in part because:
arboreal 1. fossilization is an incredibly rare process
so we can never say that we are looking at the very first of a species… that is not known, but they
- our ability to effectively survey and excavate these fossils is limited
The earliest primates and proto-‐ primates were entirely______
arboreal
what is angiosperm
flowering
when did angiosperm appear
The appearance of angiosperm (flowering) vegetation between 100 and 50 mya
what did the appearance of angiosperm result in
The appearance of angiosperm (flowering) vegetation between 100 and 50 mya created micro-‐ ecological niche that could support these early tree-‐ dwellers
what is K-T Exctinction
The Cretaceous-Tertiary (K-T) mass extinction event resulted in the extinction of three-‐quarters of the world’s reptiles, mammals and birds
when did K-T Exctinction happen
approximately 65 mya
-‐T is believed to have been caused by what
K-‐T is believed to have been caused by the impact and resulting fallout from a large (~6 mi- diameter) iridium- ‐rich asteroid or comet
what played a role in surviving the K-T Exctinction
Diet played the largest role in survivorship; omnivores and insectivores were more likely than others to survive the event
how are Physical geography and paleoclimates are very closely related
interior areas experience the harshest weather.
what did The gradual breakup of the continents do
The gradual breakup of the continents exposed more land to weather-mediating bodies of water, opening up new territory to mammals worldwide
when did The gradual breakup of the continents happen
65 mya, the planet was much warmer and wetter than it is today
do Slight changes in climate can have major impacts on the evolutionary development of certain species
yep
