1. Human Evolution

2. What is Evolution?
Evolution is decent with modification to genes, or alleles, on both small and large scales
All life on earth shares a common ancestor just as you share a grandmother with your cousins
Decent with modification gave rise to the great diversity of life that we see on earth today

3. What is Evolution?
Charles Darwin and Alfred Russel Wallace independently conceived of and described decent with modification, the mechanism for evolution
Genetic diversity in a population comes from two main mechanisms: mutation and sexual reproduction
A heritable trait that helps the survival and reproduction of an organism in its present environment is called an adaptation
Natural selection promotes the reproduction of individuals with adaptations to survive environmental change
On the Galapagos Islands, Darwin observed species of organisms on different islands that were clearly similar, yet had distinct differences

4. What is Evolution?

5. Speciation
Speciation is a lineage splitting event that produces two or more species
Speciation can occur through reduced or halted gene flow between groups within a species
Speciation can also occur to selective pressure at opposite ends of the species’ range

6. Speciation
An example of selective pressure can be seen in the peppered moth
Before the industrial revolution, the black peppered moth was rare and light bodied moths were able to blend in against tree bark and light-coloured lichen
After the industrial revolution, much of the English countryside was covered in soot from coal-burning factories
Light coloured moth were easier to see and more likely to be eaten by a predator while the black ones were camouflaged very well

7. Family Trees
A family tree is a representation of evolutionary relationships and established by studying inherited characteristics
As lineages evolve and split and modifications are inherited, their evolutionary paths diverge, producing the branching pattern
The tree of life is under constant reevaluation as new evolutionary evidence comes to light

8. Family Trees

9. How do we know what happened when
Radiometric dating relies on half-life decay of radioactive elements to allow scientists to date rocks and materials directly.
Stratigraphy provides a sequence of events from which relative dates can be extrapolated.
Molecular clocks allow scientists to use the amount of genetic divergence between organisms to extrapolate backwards to estimate dates.

10. A brief history of humans
Humans did not evolve from chimpanzees.
Humans and chimpanzees are evolutionary cousins and share a recent common ancestor that was neither chimpanzee nor human.
Humans are not "higher" or "more evolved" than other living lineages.
Since our lineages split, humans and chimpanzees have each evolved traits unique to their own lineages.

11. A brief history of humans
15 Million Years ago – Great Ape ancestors speciate from the ancestors of the Gibbon
13 Million Years ago – African ape ancestors speciate from ancestors from the ancestors of the orangutan
10-4 Million Years ago – the latest common ancestor of humans and chimpanzees
Proposed candidate for the chimpanzee-human latest common ancestor, Sahelanthropus tchadensis, lived about 7 million year ago

12. A brief history of humans
A climate change event 7 to 6 million years ago reduced forests in west Africa and early human ancestors developed upright walking behaviour for increased ground travel
4.5 – 2 Million Years ago – Australopithecus is an early ancestor of modern humans
They were the first of the human ancestors to retain a gene which increase the ability of neurons in the brain
Previously, this gene would have been metabolically expensive and decrease an individual’s fitness
Cooperation among individuals allowed human ancestors to thrive on the savannah of Africa

13. A brief history of humans