Larson 5

Darwin's book led to almost complete acceptance of evolution by the scientific community within 20 years

• by providing a partial mechanism
• because science was becoming so focused on naturalism (do not use supernatural explanations such as direct creation by God while doing science)
  
• the idea that species are related in a family tree made sense of so many patterns, particularly when you add the fossil record
  

• descent with modification: species are related in a family tree (evolution)
• some other process (such as inheritance of acquired characteristics--Lamark) could cause the modification
• evolution by natural selection of small random variations (Larson will call this Darwinism)

Descent with modification was widely accepted in just a few years and within 20 years no controversy remained among mainstream scientists in the English-speaking world: all had adopted it

• but there was still controversy about natural selection and over the source of variation and some still saw God's plan in the pattern of development of new species
• modified ideas were popular in Germany from the tradition of German idealism (species are ideal types)
  

The idea caught on so quickly because it met the needs of science

• Darwin's theory fits the political and social situation of the time (British empire was justified by survival of the fittest, Germany wanted to be fittest)
  
• The idea of descent with modification made sense of the patterns scientists saw and was a good source of hypotheses for research--adopted because it led to fertile new scientific questions
  
• scientists embraced the idea of using only naturalistic explanations, that supernatural causation had no place in science
• the older generation was pushed aside, eg. Richard Owen (who had proposed the apparent similarity of species was due to archetypes used by the creator)
  
• note p. 111, even promoter of theistic evolution George Frederick Wright, wrote "we are to press known secondary [material] causes as far as they will go in explaining facts.  We are not to resort to an unknown (i.e., supernatural) cause for explanations of phenomena till the power of known causes have been exhausted.  If we cease to observe this rule there is an end to all science and all sound sense."

A great deal of research interest in the relationship between species and missing links

• Earnst Haeckel: Ontology (or ontogeny) recapitulates phylogeny: related animals look the same in early fetal development because the development of the fetus retraces the evolution of the species
• this is not as clear as Haeckel made it, but at the time it was seen as overwhelming evidence for evolution
• Haeckel took his ideas in the direction that evolution validates competition between nations (survival of the fittest between ethnic groups which he called races, not between individuals)
• this was used by the Nazis--science is sometimes used as a source of authority by politicians
  
• Alfred Russel Wallace investigated biogeography--the distribution of species.  How different animals were on isolated islands provided important evidence for evolution
• Wallace believed that a spiritual influx created humans and that our mission was to abolish the cruelty of natural selection
  

New Zealand was particularly unique because of its extreme isolation

• 89% of native plants are endemic (exist nowhere else in the world)
• many familiar kinds of animals were missing and other animals had taken those niches
  
• before the aborigines (Maori) arrived there were no land mammals but the bat (therefore birds took many of the ecological niches usually taken by mammals--for example, the only large grazing animals were birds)
  
• also the culture of the people was unusual

Another animal filling the niche of the mouse was the Stephens Island Wren

A flightless songbird--one of only three flightless songbirds ever known and the world's smallest

• Lived on a one square mile island off the northern tip of the South Island--a remnant of the ecosystem as it had been before the Maori brought with them rats
  
• "It was only seen live on two occasions when it was disturbed from holes in rocks. It was thought to have been semi nocturnal and ran very fast like a mouse." (source)
  
• At the Ornithologists Club in London in 1894 a collector proudly displayed 10 specimens of the wren that had been killed by the lighthouse keeper's cat
• He also announced that the species was now extinct due to the cat
  

the largest flightless birds, the moas, filled the niche of grazing animals

All 11 species of Moa were hunted to extinction by the Maori in the 13th and 14th century.  They only laid one or two eggs at a time and took 10 years to grow to maturity so were wiped out easily.

"Second only in weight to the extinct elephant bird of Madagascar, the largest moa was the tallest bird on earth, with the top of its' back 6 feet above the ground" (source)

The largest Moa still weighed over 500 lbs.  They ate mostly bushes and the lower branches of trees.  Their beaks were strong

The Haast's eagle, with wingspan of 3 meters, preyed on the Moa and died out with it

While evolution had become the basis of biology by the end of the century, natural selection was still controversial

• William Thomson, Lord Kelvin gave evidence from physics that the earth could not be old enough for gradual natural selection (his physics was good but he did not know about radioactivity as a source of heat inside the earth)
• without a theory of genetics it was very difficult to talk about how characteristics accumulated.  Swamping: if offspring were simply a blend of their parents then new characteristics would disappear.  Fleeming Jenkin proved this mathematically.
• Darwin had a theory of gemmules that came close to Mendelian genetics, but he also accepted inheritance of acquired characteristics to speed up evolution

Four alternative mechanisms for evolution, alternative theories to Darwinism (gradual random variation selected by natural selection):

• Theistic evolution: God creates variations according to a plan
  
• Lamarkianism: inheritance of acquired characteristics
• orthogenesis: developmental trends continue whether or not they are immediately beneficial
  
• saltation: large mutations provide the variations