Geology

Geology provides us with two pieces of evidence, the first is the age of the earth, the second is the presence of remains of ancient forms of life (fossils).

Three views of geology

	Gradualism (Hutton)	Profound changes can be the result of small changes over long periods of time.
	Catastrophism (Cuvier)	Recurrent catastrophic events causing widespread extinction and resulting in sharp boundaries between fossil layers.
	Uniformitarism (Lyell)	The same processes we see today also acted in the past.

Age of the earth

Darwinian evolution requires an ancient earth. Evidence for an ancient earth comes from the enormous amounts of time needed to build up the layers of sedimentary rock we can see in cliff faces and canyons. Campbell: see page 416, fig. 22.2

A Glaswegian perspective: Lord Kelvin and the Age of the Earth Leading physicist of 19th Century (professor of Physics at Glasgow University) (absolute temperature scale named after him) Argued from rate of cooling of the earth that it was about 98 Myrs old Similar result from estimating the age of the sun Darwin estimated the Sussex Weald cliffs had taken 300 Myr to form Resolution: Kelvin did not know that the source of the Sun's energy is nuclear fusion

Fossils

Fossils provide us with direct evidence of transformation.

Fossil whales show well develped hind limbs and less modified skeletons (Campbell: see page 423, fig. 22.8)
	Pakicetus skull Rodhocetus skeleton

While some vertebrate fossils are spectacular, microfossils provide clearer evidence of transition.

Correlation with taxonomy

As well as evidence of transformation, there is a correlation between the order in which living forms occur in the Linnean heirarchy and the order in which they appear in the fossil record.

[Ridley here]