Lec 2: The Developmental Hypothesis - Directed Variation, Fossil Record Flashcards
John Ray (1627 - 1705)
Unlike most in the 17th C, thought fossils were once living (and not from non-natural causes, e.g. something from Creation)
- > some fossils formed with Noah’s flood, but then why were fossils left on high dry land
- > Ocean once covered world, slowly receding to expose land
- > didn’t think God would let animals go extinct, so must be undiscovered species
Georges Cuvier (1769 - 1832)
and Alexandre Brongniart (1770-1848)
a) Catastrophism
b) Principle of Organic Correlation
By 19th C, most realised fossils were organic remains, mostly of extinct species.
- > laid groundwork for what became “catastrophism”
- > Paris Basin showed layers of freshwater/marine
- > thought it showed different floodings
- > must be rapid/sudden disasters
- > saw fossils in chronological order of creation
- > older the strata, the more extinct
- > no humans, so we appear between 2nd and 3rd last catastrophe (since the last one was Noah)
- > reputation for studies and his high offices, Pterodactyl
- > so influential he made Geology identical with natural history
Evidence for Catastrophism
Two main pieces:
1) Evidence of large scale devastation
- >lava flow
- >interchange of marine and terrestrial in strata
2) Organisms changed massively with catastrophes
Cuvier’s “Principle of Organic Correlation”
Basic on Aristotelian principle of subordinate parts of the whole
- > all organs form one system
- > parts belong together, act/react upon each other
- > just one organ wouldn’t change
- > e.g. if canal evolved for flesh, jaws/sight/claws too!
- > from one part, we can infer about the rest
Cuvier and Origin of Species, Evolution?
Demonstrated fossils that aren’t present today
- > dangerous for his religious beliefs
- > if they ded and species immutable, what are today’s fauna? God only made one set of animals
- > suggested God taught primitive Hebrew tribes morality not palaeontology, scripture not the entire truth
- > creation is A SERIES of creations/destructions
- > scripture only tells the most recent creation; he was teaching us morals not history
Opposed evolutionary hypothesis. Disagreed with Lamarck, who thought there were “transitional forms” between species.
- > “basic form” of species can’t change, else unviable
- > divided animals into 4 classes, which are unrelated
- > vertebrates, mollusks, articulata, radiata
- > if evolution existed, there should be no gaps in the fossil record (but there are)
Jean Baptiste Lamarck (1744-1829)
Professor of Zoology, a botanist who worked heavily with invertebrates.
Great Chain of Being
- > steps that simple life climbs
- > every species climbs in lockstep
NEW SYSTEM FOR CLASSIFYING INVERTEBRATES
Believed in progressivist philosophy; world moving in desirable direction. Science > truth & enlightenment.
- > believed in imperceptibly slow development
- > saw correlation between adaptations & environment
- > Creator didn’t actually give perfectly adapted things
- > and the world isn’t actually static, geological evidence
1802, identifies that same evolutionary processes produce humanity.
->but how do we have higher faculties - reason, spirituality?
Lamarck, Extinction and Evolution?
Cuvier showed extinction, how to explain it?
->man made, catastrophe? But why so many aquatic?
Maybe they aren’t extinct at all?
->Lamarck believed they all migrated to unexplored area
->or they all evolved
Lamarck denied Extinction
- > no explanation unless Man hunted them down
- > Shellfish are protected, impossible all ded
- > they must have evolved
Believed in a “path” or “order” nature followed
->modern life “developed” from fossil ancestors
1) Simple animals spontaneously generated
2) They evolve, pushed by a force promoting complex structures
- >caused by new conditions = new needs = new habits 3) Organs strengthen/weaken through use/disuse
- >new organs formed and passed on to offspring
But he couldn’t explain how acquired traits were passed to offspring.
