HE - methods to study human evolution

Evolutionary history of a taxon including hypotheses about ancestors and descendants

Method by which branching patterns of a phylogeny are generated
Based on shared character states of different taxa

Taxa, genes, fossils etc.

Molecular/morphological characters

Graphic representation of evolutionary relationships between different taxa

Different taxa

Choose OTUs
Choose relevant characteristics and record presence/absence
Create matrix

Doesn't account for homoplasy
Some characteristics evolved separately and independently in different species

Group of organisms that comprises of the most recent common ancestor and all its descendants

Group of organisms that comprises the most recent common ancestor but NOT all of its descendants (only 1)

Derived trait caused by evolutionary change

Derived trait confined to a single taxon
Type of apomorphy

Trait retained from an ancestor

Character shared by different taxa but not inherited from a common ancestor
Evolved independently in each species

Cladograms:
Represent hypothesis about evolutionary relationships between groups of taxa as a series of branching events
Phylogenies:
Represent hypothesis of true evolutionary history by incorporating the concept of time

Believed non-human apes more closely related to each other than modern humans

Chimps and humans more closely related to each other than to gorillas etc.

2009
Independent evolution of knuckle walking in African apes shows that humans did not evolve from a knucle walking ancestor

Remains of an organism

Study of factors involved in fossilisation

Underground cave system formed by dissolution of soluble rocks

Collapse of surface layer

Carnivore den
Accidental falls
Deliberate disposal

Rapid decomposition
Decay too quick to be buried
Acidic soils

Science of dating

Absolute dating (exact)
Relative dating (approximate)

Radiometric dating methods - 14C, uranium series, potassium/argon
Electron Spin Resonance (ESR)
Luminescence
Cosmogenic
Molecular clock

Biostratigraphy
Palaeomagnetism

Decay of radioactive isotopes

Same number of protons and electrons, but different number of neutrons

Time required for one half of the atomic nuclei of a radioactive sample to decay

Isotopes that are unstable decay into more stable isotopes

Decay is highly predictable

Stalagmites/stalactites

14C
Uranium to thorium
Uranium to lead
Potassium to argon

Accumulation of e- in certain minerals that are received from radioactive decay in the materials that surround it

Estimating dose a sample has received
Measuring dose rate generated by surroundings

Dating things up to 2 mill years ago
Dating speleothems and organic materials

Estimates how long ago mineral grains were last exposed to sunlight or sufficient heating
Buried sediments receive radiation from surrounding isotopes, building up radiation dose
Short daylight exposure causes the dose to be emitted
Exposure to sunlight/heat resets optically stimulated luminescence (OSL) dating clock

When looking at a key event in history (eg. heating)

Uses mutation rate of biomolecules to deduce when 2 taxa diverged
Looks at DNA/RNA/aa

- Mutation rate is per generation, generation time evolves
- Species differ in mutation rate
- One site may mutate several times, only 1 can be detected

Correlation of stratigraphic units using fossils
Comparing type of animal that exists in a particular site to other site where the same animal has been found

Statistically random change in Earth's magneitc field

Dating based on polarity of Earth's magnetic field at time layer was deposited
Polarity of magnetic field recorded upon deposition

To date volcanic deposits

Long periods of consistent polarity