Download The Darwins & Evolution

The Darwins
•
•
•
•
•
•
Erasmus Darwin (1731 - 1802)
Charles Darwin (1809 - 1882)
Erasmus:
Physician and botanist.
Published many of his thoughts in the form of poetry.
One of a group of intellectuals who fueled the
industrial revolution.
• Wrote on many topics, responsible for early forms of
many inventions and progressive medical treatments
• Big supporter of French and American revolutions.
Erasmus Darwin continued
• Friend of Benjamin Franklin.
• Politically progressive, what we would
today call liberal.
• Inspiration for Frankenstein.
• Writings include many accurate
predictions.
Erasmus had some good and
bad ideas about plants:
•
•
•
•
"How the young rose in beauty's damask pride
Drinks the warm blushes of his bashful bride;
With honey'd lips enamour'd Woodbines meet,
Clasp with fond arms and mix their kisses sweet”
• Searched for plant brain, never found it.
• Misunderstood role of bees - thought they “stole” honey
from plant.
Erasmus on Evolution:
"Ere Time began, from flaming chaos hurled
Rose the bright spheres, which from the circling world;
Earths from each sun with quick explosions burst,
And second planets issued from the first.
Then whilst the sea at their coeval birth
Surge over surge involved the shoreless earth;
Nursed by warm sun-beams in primeval caves
Organic life began beneath the waves.....
Hence without parent by spontaneous birth
Rise the first specks of animated earth;
From nature's womb the plant or insect swims,
And buds or breathes with microscopic limbs."
Erasmus on Evolution
“Organic life beneath the shoreless waves
Was born and nurs'd in ocean's pearly caves
First forms minute unseen by sphearic glass
Move on the mud, or pierce the watery mass;
These, as successive generations bloom,
New powers acquire and larger limbs assume;
Whence countless groups of vegetation spring
And breathing realms of fin and feet and wing"
Erasmus Darwin - overlooked
• Pre-dates Lamarck and clearly understands
evolution better.
• More Erasmus quotes
• Made powerful political enemies.
• Public decline.
• Conservative son, Robert, father of Charles.
• Influences on Charles Darwin, known from
Charles’s notes in margins of his
grandfather’s works.
Charles Darwin
• Not interested in being a doctor.
• Undergraduate at Cambridge - supposedly to
study theology but more interested in natural
history.
• Learned more about his Grandfather in
college.
• Recognized as talented by his teachers.
• Voyage of survey ship Beagle 1831 - 1836.
• Darwin “hired” as naturalist and gentleman’s
companion.
Darwins Father doesn’t approve:
•
•
•
•
•
•
•
•
Such a voyage would reflect badly on his future prospects as a
member of the clergy.
The entire plan seemed adventurous and wild.
Why was a naturalist still being considered so close to the start of the
voyage?
Given the above, other people must have been considered. Why had
they refused the offer?
Going on the voyage would prevent Charles from settling down to a
real life.
The accommodations on the ship would be very poor.
The voyage would offer Charles another excuse to change his focus in
life.
It would be a complete waste of his time.
Darwin’s return to England
• Health problems after return.
• Many publications:
Voyage of the Beagle
Geological Observations of Coral Reefs
Descent of man
Origin of species
Others major publications on barnacles, orchids, plant tropisms,
The variation of plants and animals under domestication,
various diaries and other shorter works, and his biggest blunder,
a theory called “pangenesis” which was a variation of Lamarck’s
ideas used to explain the origin of variation.
• Published “Origin of Species” in 1859.
• Terrible gas.
Evolution by natural selection; Darwin’s arguments:
•
•
•
•
All organisms produce many offspring.
Most will die - hence struggle for survival.
Organisms vary.
Some organisms survive better than others - they have a better
combination of traits.
• Traits tend to be inherited - offspring resemble parents.
• Favorable traits tend to be passed on.
• “Favorable” means anything that increases reproductive rate.
Hence, the theory also explains sexual selection and domestic
variation.
Early 20th century developments:
• Work of Mendel and others leads to understanding of genetics.
• Understanding of factors other than selection such as genetic drift
and meiosis
• Population genetics makes mathematical predictions that are
confirmed in the lab. (eg Hardy-Wienberg Law)
• New understanding of evolutionary implications for development,
cell biology, hybridization and other phenomena.
• Phylogeny replaces taxonomy as primary goal of biology.
• Understanding of evolution at the molecular level, ie: how DNA
changes.
• Collectively called the “new synthesis”, “neo synthesis” or “neo
Dawinism”
Late 20th century additions
• 1956 - DNA structure revealed.
• Explosive growth of new molecular techniques continues to reveal
mechanisms by which evolution occurs and helps unravel
evolutionary history:
• molecular cladistics
• molecular clock
• role of mutations and mutator genes
• better understanding of recombination
• introns, psuedogenes and the modular arrangement of genome,
“jumping genes” (transposons) (McClintock), role of viruses, subcellular symbiosis (Margulis) and many other phenomena are
known to contribute to evolution at the molecular level.
Evolution evidence summary:
•
•
•
•
•
•
•
•
•
•
•
•
•
Fossil
Hierarchy and homology
Biogeography and distribution
Observed changes in domesticated organisms and "artificial selection”
Sub-cellular symbiosis
Population genetics (eg Hardy-Wienberg)
Other mathematic models
Molecular data - psuedogenes and gene lineages, observed and manipulated
molecular evolution.
Molecular clock - comparison to geology and known biogeography.
Observed speciation events
Development
Vestigial structures (no longer used) and atavisms (sudden reappearance)
More evidence