HISTORY 60

Department of History
University of California, Irvine
Instructor:    Dr. Barbara J. Becker
 

Lecture 17.  Struggle and Survival.

 
Charles Darwin (1809-1882)

Events in the Life of Charles Darwin

1809
• born
1828-1831
• student at Cambridge University
• developed interest in geology
1831
• began voyage on Beagle
1835
• experienced earthquake in Chile
• explored Galapagos archipelago
1836
• returned to England

Voyage of the Beagle (1831-1836)

Resolving the "Mystery of Mysteries"

The Galapagos Islands

Events in the Life of Charles Darwin (cont'd)
October 1836
• returned to England from Beagle voyage
January 1837
• donated Galapagos specimens to Zoological Society of London
March 1837
• met with ornithologist, John Gould
• all Galapagos birds are species of finch
September 1838
• read Essay on ... Population by Thomas Robert Malthus (1766-1834)

Cactus-feeding Galapagos finches, drawn by ornithologist John Gould

Lessons from the Finches

excerpts from Darwin's Journal of Researches (1839)

[I]n the thirteen species of ground-finches, a nearly perfect gradation may be traced, from a beak extraordinarily thick, to one so fine, that it may be compared to that of a warbler.  I very much expect, that certain members of the series are confined to different islands....

Seeing this gradation and diversity of structure in one small, intimately related group of birds, one might really fancy that, from an original paucity of birds in this archipelago, one species had been taken and modified for different ends.

Lessons from Malthus

"Struggle for existence" involves:

  • struggle with environment
  • struggle with other species (predator/prey)
  • struggle with similar individuals
Any advantage, however small, makes a difference.

Any difference, however small, can be an advantage.

Artificial selection as practiced by breeders is a practical model for natural process of selecting fittest individuals.

Events in the Life of Charles Darwin (cont'd)

1842
• completed 35 page "Sketch" outlining theory of descent with modification
1844
• completed 230 page "Essay" detailing his theory
 
Vestiges of the Natural History of Creation published by anonymous author [Robert Chambers (1802-1871)]

excerpt from Vestiges....

These facts clearly shew how all the various organic forms of our world are bound up in one--how a fundamental unity pervades and embraces them all, collecting them, from the humblest lichen up to the highest mammifer, in one system, the whole creation of which must have depended upon one law or decree of the Almighty, though it did not all come forth at one time.

Events in the Life of Charles Darwin (cont'd)

1844-1854
• Darwin honed his argument through rigorous study of barnacles
1856
• began work on massive treatise on natural selection and evolution
1858
• received manuscript from Alfred Russel Wallace:  On the Tendencies of Varieties to Depart Indefinitely from the Original Type

Alfred Russel Wallace (1823-1913)

excerpts from
On the Tendency of Varieties ... (1858) by Wallace
It is ... "a struggle for existence," in which the weakest and least perfectly organized must always succumb....
[S]o long as a country remains physically unchanged, the numbers of its animal population cannot materially increase.

If one species does so, some others requiring the same kind of food much diminish in proportion....

[T]hose that die must be the weakest--the very young, the aged, and the diseased,--while those that prolong their existence can only be the most perfect in health and vigour--those who are best able to obtain food regularly, and avoid their numerous enemies....

...Most or perhaps all the variations from the typical form of a species must have some definite effect, however slight, on the habits or capacities of the individuals.

Even a change of colour might, by rendering them more or less distinguishable, affect their safety; a greater or less development of hair might modify their habits....

Events in the Life of Charles Darwin (cont'd)

1859
• Darwin published On the Origin of Species by means of Natural Selection ...
Differences between Darwin and Wallace on Speciation
Darwin
Wallace
struggle between individuals struggle between individuals and environment
artificial selection analogous to natural selection not convinced that animal breeding is legitimate model
colorful plumage results from sexual selection of males by females colorful plumage results from inter-male combat
man is an animal like any other man is a special creation
Problems with Natural Selection
  • animal altruism
    •  
      Can cooperation be an adaptive feature?
  • vestigial parts
Why do organisms retain useless organs?
  • heat death of the universe
How long can the sun burn at its current rate?
  • inheritance of characteristics
How can one individual spawn a new line of organisms?
Evolutionary Trees

Sketch from Darwin's Notebook

"Pedigree of Man" from Generelle Morphologie der Organismen (1866) by Ernest Haeckel (1834-1919)

Darwin's Theory of Pangenesis (1868)
If animals and plants grow by cell division, what insures that daughter cells will resemble parent?
  • Proposed existence of gemmules (from Latin root word for "twinning")
    • granules given off by all cells
    • some are dormant, others expressed
    • contain formula to program the growth of new cells
    • travel to, and concentrate in reproductive organs
  • Heredity is the passing on of these gemmules.

If new cells inherit patterns from parents, what accounts for variations among offspring?

  • Proposed that disturbance in this process:
    • environmental changes
    • level of competition
    • food supply...
  • causes variations:
    • number of gemmules increased or decreased
      • result--ordinary variations
      • manifestation--individuality of people
    • modification of gemmules themselves
      • result--new structures
      • manifestation--major change in form and function
  • This is the variation that natural selection acts on.
 
Go to:
  • "Monkeyana" (1861) a poem by Gorilla of the Zoological Gardens; and
Weekly Readings
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Lecture Notes
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Quodlibets
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