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Evidence for evolution: Fossils
John Murray
Evidence for evolution: Fossils
As told by a series of
&
papers
Oxford Dictionary:
“the remains or impression of a prehistoric plant or animal embedded in rock and preserved in petrified form””a person or thing that is outdated or
resistant to change”
Fossils
Usually formed from hardest, most resistant parts of organisms
(but not always)
Sedimentary rocks
Fossil record is incomplete
Fossils
(1) Organismic Incompleteness
Fossil record is incomplete
Fossils
Fossil record is incomplete
(2) Stratigraphic Incompleteness
Effect of varying rates of deposition on apparent rates of change in the fossil record. The numbers refer to
equal lengths of time.
Fossils
Fossil record is incomplete
(3) Ecological Incompleteness
Fossils
49Ma: Grube Messel
Fossil record is incomplete
So why bother at all with fossils?
1. Tangible evidence for evolution
2. (Palaeo) ecology & ethology
3. Evolutionary rates
4. History of Life
Fossils
150Ma: Solnhofen
A snapshot
1.Tangible evidence
for evolution
Caudipteryx zoui
2. (Palaeo)ecology & ethology
1859: Darwin’s Origin of Species
3. Evolutionary rates
time
morphology
Darwinian view:
‘Classical’ Phyletic
gradualism
time
morphology
Key points: Evolutionary rates remain
constant through speciation event.
Small changes seen gradually through
generations. Darwin’s ‘Paradigm’
1970s: Eldredge & Gould:
Punctuated Equilibrium
Punctuated Equil ibrium
time
morphology
Key points:• Evolutionary
rate very low (0) over long periods • Speciation in
short periods of time with rapid rates of change.• Eldridge &
Gould argued that this model most closely resembles the evidence from fossil record.
Debate about which model is more appropriate has continued to present
Punctuated EquilibriumPhyletic Gradualism Vs
15,000 trilobites!
Peter Sheldon
4. History of Life
History of E a r t h
Base of Palaeogene
Terrestrialisation
Zachelmie trackway
Evolution & the tree of life
(the state of the art)
Phylogenetic tree:Lancelet(outgroup)
Lamprey
Bass
Frog
Turtle
Leopard
Vertebralcolumn
Hinged jaws
Four walking legs
Amnion
Hair
Fossils?
Time?
Stem Group
Crown Group
Origin of major animal groups (Phyla)
(Stem – Crown groups get really tricky here!)
Erwin et al. Science 334, 1091-7 (2011)
4. History of Life
Fig. 3. Detailed stage-level depiction of the animal fossil record as compared to the molecular divergence estimates for 13 different animal lineages. Shown in thick black lines are the known fossil records of each of these 13 lineages through the Cryogenian-Ordovician; most lineages make their first appearance in the Cambrian, consistent with the known fossil record of all animals. Further, the extent of these stratigraphic ranges closely mirrors the molecular estimates for the age of each of the respective crown groups (red colored circles), highlighting the general accuracy of the molecular clock. Only cnidarians have an unexpectedly deep crown-group origination as estimated by the molecular clock, as the deep demosponge divergence is apparent from taxon-specific biomarkers (gray bar).
Erwin et al. Science 334, 1091-7 (2011)
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