Lec 3: Deep Geological Time Flashcards
Charles Lyell (1797-1875)
Defender of the UNIFORMITY THESIS
- past causes have always operated at same rate and intensity as they do now
- Earth is great machine, always working same way
He thought biological life followed Uni of State
- > what exists today was like that from the beginning
- > unlike others, who would only believe the physical world would stay constant
- Saw physical - life link as direct and necessary*
- > species are perfectly adapted for surroundings
- > if life changes, it’s only mirroring physical change
- > so if climate & geography uniform, life is non-directional
Problem with fossil record, fish>reptile>mammal>human
->breaks two arguments
However after 25 years of no Paleozoic mammals, he concedes
- > doesn’t deny the possibility of evolution & progress
- > a “minor shift”; his prior denial was just skepticism because of insufficient data
Lyell & Uniformity Hypothesis?
- > what are the types?
- > and who is strongly associated with each (esp Lyell)
Defended at least four versions of it, in “Principles of Geology”
->State is his jam.
1) Uniformity of Law (Burnet)
- >laws of nature are same in every space/time
- >accepted by Burnet/Leibniz but rejected by Newton
2) Uniformity of Process (Newton)
- >if past phenomena can be explained with current processes, don’t invent new ones
- >exhaust the known ones before invention
3) Uniformity of Change
- >change is slow, steady, gradual
- >Geological phenomena (e.g. Niagara) are accumulation of numerous tiny insensible changes
- >catastrophes (e.g. floods) are just local events; planet as a whole continues slowly
4) Uniformity of State (Lyell)
- >Earth follows no vector of progress
- >planet always like it is now
- >always changing, but the change leads nowhere
- >e.g. land&sea may change positions, but remain in same proportions
His predecessors widely accepted uniformity, but Lyell was different in his UNIFORMITY OF STATE
- > extended it all the way to organic change
- > unlike catastrophists, he said beginning and ends are distributed through space and time, not concentrated in mass death periods
- > said life has no progress in organisation/complexity
- > species are endowed at creation with traits
- > thought we’d find fossils of Paleozoic mammals
How does Lyell tackle the fossil record?
a) Advanced vertebrates are in earlier strata; yet to be discovered.
- fossilisation is biased towards the direction shown
- e.g. birds are “advanced” but will rarely fossilize
- most explorations in Europe/NA, which is a small area and an ocean during Paleozoic
- they recently found Mesozoic mammals, which they previously missed and only found in Tertiary rock
b) If animals aren’t found, the absence is reversal consequence of climatic change
- >species are perfectly adapted to climates
- >trend towards cold climates (which favours mammals) will reverse eventually
- >if cold brought vertebrates to North, a summer would bring back ancient animals
