The Darwins

1
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.

2
Erasmus Darwin continued

• Friend of Benjamin Franklin.
• Politically progressive, what we would today call
  liberal.
• Inspiration for Frankenstein.
• Writings include many accurate predictions.

3
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.

4
Erasmus on Evolution

• "Ere Time began, from flaming chaos hurledRose
  the bright spheres, which from the circling
  worldEarths from each sun with quick explosions
  burst,And second planets issued from the
  first.Then whilst the sea at their coeval
  birthSurge over surge involved the shoreless
  earthNursed by warm sun-beams in primeval
  cavesOrganic life began beneath the
  waves.....Hence without parent by spontaneous
  birthRise the first specks of animated
  earthFrom nature's womb the plant or insect
  swims,And buds or breathes with microscopic
  limbs."

5
Erasmus on Evolution

• Organic life beneath the shoreless wavesWas
  born and nurs'd in ocean's pearly cavesFirst
  forms minute unseen by sphearic glass Move on
  the mud, or pierce the watery massThese, as
  successive generations bloom,New powers acquire
  and larger limbs assumeWhence countless groups
  of vegetation spring And breathing realms of fin
  and feet and wing"

6
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
  Charless notes in margins of his grandfathers
  works.

7
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 gentlemans
  companion.

8
Darwins Father doesnt 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.

9
Darwins return to England

• Health problems after return.
• Many publicationsVoyage of the
  BeagleGeological Observations of Coral
  ReefsDescent of manOrigin of speciesOthers
  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
  Lamarcks ideas used to explain the origin of
  variation.
• Published Origin of Species in 1859.
• Terrible gas.

10
Evolution by natural selection Darwins
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.

11
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

12
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, sub-cellular
  symbiosis (Margulis) and many other phenomena are
  known to contribute to evolution at the molecular
  level.

13
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