Transcript Beginnings of Evolutionary thought

Beginnings of
Evolutionary thought
Pre- Darwin
Four Problems with
Creation
• 1 – fossils
• 2 – age of earth
• 3.- homology – anatomical
studies.
• 4 - zoogeography
Nils Stensen,
(Steno)
1638 - 1686
The rocks themselves formed from
fluids laying down sediment with the
fossils enclosed. He could see that
larger particles are at the bottom.
He could even tell if it was salt or
fresh water. Most important, rocks
are deposited flat, layer by layer, the
bottom layer being first. This is the
first presentation of the theory of
superposition of strata, so important
to geology and this course. The
theory of superposition is that when
one stratum was forming, the one
above it had not yet formed. There
was a time sequence involved.
What are Fossils??
In 300 B.C.,Theophrastus, a student of Aristotle
attributed bones in rocks to ‘plastic virtue’, a
characteristic of the rocks that caused the bones to
grow within them. The rocks almost have a
predisposition to turn into life.
Steno did not accept this explanation for the
tonguestones. He made the observation, based on
careful measurements, that they were shark teeth.
His problem was to explain how they got into the
rock. He concludes that the matrix (stuff surrounding
the tooth) was not hard when the tooth was
incorporated. There was no deformation around the
tooth, as would occur if it grew after the rock had
solidified. At one time, either the water was higher
or the land was lower. (major modification of
thinking).
Note: Abiogenesis vs Biogenesis
Georges Cuvier
August 23, 1769 – May 13, 1832
“Cuvier's scientific achievements are difficult to
overestimate. It was widely recounted that he
could reconstruct a skeleton based on a single
bone. His work is considered the foundation of
vertebrate palaeontology.”
Nearly complete skeleton of
Paleotherium minus from the
Paris Basin
after Cuvier, 1825
Recognition of fossils as life
pre-human.
William Smith, Father of
historical geology
1769-1839
canal
Smith’s ideas
1. You can map strata by fossils
2. kind of fossils varies with age
Pleistocene = 90% living
forms
Miocene = 60 % living forms
Eocene (dawn of life)
only 10% living forms
3. superposition. Pleistocene on
top, Eocene on bottom.
If you look at the strata, you occasionally see an
uncomformity. What is its cause and what does it
represent?
Catastrophism is the doctrine
proposed by the remarkable French
zoologist and comparative
paleontologist, Georges Cuvier (17691832), that major changes in the
earth's crust result from geologic
catastrophes, such as eruptions of
“supervolcanoes”*, rather than by slow
evolutionary processes, such as
alluvial depositions and small volcanic
eruptions
Cuvier’s study of fossils in rock strata in the environs of
Paris led to one of his greatest discoveries: species
become extinct. This idea was understandably hard to
swallow for many people in the 19 th and 20 th centuries
and even today because of its corollary that humans
might one day become extinct. Even though Cuvier
detested “theories” and strongly advocated “facts”, he
expertly laid out his own theory on species extinction in
his very readable “Discourse on the Revolutionary
Upheavals on the Surface of the Globe and on the
Changes which They Have Produced in the Animal
Kingdom” published in 1825**.
Cuvier's example of an unconformity and faunal
succession
Charles Lyell 1797-1875
James Hutton 1726-1797
The ideas behind uniformitarianism originated with the
work of Scottish geologist James Hutton. In 1785,
Hutton presented at the meetings of the Royal Society of
Edinburgh that the Earth had a long history and that this
history could be interpreted in terms of processes
currently observed. For example, he suggested that
deep soil profiles were formed by the weathering of
bedrock over thousands of years. He also suggested
that supernatural theories were not needed to explain
the geologic history of the Earth.
• So – unconformities = major
events – the flood of noah for
instance.
• Or – simply periods of nondeposition
• Proof of uniformitarianism –
find missing sediments
elsewhere on earth.
• Note: both theories are
extremes. We have had
catastrophic events (meteors
etc.) – but not universal.
• Also – for slow changes to
occur, need a lot of time.
Homology vs analogy = relationships of structure
1707 -1788
Comte de Buffon
Homology
Mt Ararat
Early Evolutionary
theories
Jean-Baptiste Lamarck (1744-1829)
Inheritance of acquired
characteristics
Lamarck believed that giraffes
stretched their necks to reach
food. Their offspring and later
generations inherited the
resulting long necks. [
Lamarck expressed the idea that by simply using or not
using certain organs they may be developed or atrophied
and their offspring can then inherit these acquired
characteristics. (Milner p. 375, 1993) It should be noted
that this theory was not widely accepted largely due to the
fact that the French word that Lamarck used in the sense of
“must” was translated as “wants to,” which makes it sound
as though the organism decides to change its body.
Furthermore, Lamarck provided no mechanism by which
this could take place.
(www.ridgenet.net/do_while/sage/v1i8f.htm) Darwin was
the one to give a mechanism for Lamarck’s idea. This
mechanism is known as pangenesis.
In the late 1860s Francis Galton, the cousin of Charles
Darwin, Galton went further into Darwin’s theory of
Pangenesis hypothesizing “that combination of gemmules
might be conveyed by the blood to growing parts of the
body, or passed to other bodies by reproductive organs,
thereby passing on characteristics.” In order to test his
hypothesis Galton gave blood transfusions between
rabbits to see “whether changes of blood accelerated the
appearance of inherited characteristics in offspring.”
However, he could not conclude that the transfusion
altered successive generations