Darwin, Reluctant Radical

Evolutionary thinking before Darwin:

• Plutarch: contrasting the Syrians vs. Anaximandros

  • Syrians: believed everything came at once

  • Anaximandros: believed and saw similarities

    • that first man came from fishes → aka shared common ancestor

Twitter: Evolution in 140 characters

• Time + lucky changes = evolution

• consists of random changes

• lucky changes = more offspring = more offspring inherit lucky changes

Evolution: Definitions

• “Evolution (changes) are there that are inheritable via the genetic material from one generation to the next. Biological evolution may be slight or substantial; it embraces everything from slight changes in the proportion of different alleles within a population (such as those determining blood types) to the sucussive alterations that led from the earliest protoorganism to snails, bees, giraffes & dandelions”

• “In fact, evolution can be precisely defined as any changes in the frequency of alleles within a gene pool from one generation to another”

Scala Naturae

• realm of being

• realm of becoming

• persumes humans are at the top/ultimate pinicle of evolution

  • believe humans are endpoint (thinking)

Scala Naturae & “Progressive Evolution”

• thought things are becoming more advanced/more evolved

Cardus Linnaeus

• analyzed traits of thousands of life forms; devised first taxonomic system

  • kingdom

    • phylum

      • class

        • order

          • family

            • genus

              • species

• orginally placed chimpanzees in the “human” family, as homo troglodytes

• mostly creationist scientific community of 18th century restructured taxonomies so that chimps, gorillas, orangutans would be in their own genus, separate from humans

• “I demand of you…that you show me a generic character…by which to distinguish b/w Man & Ape. I myself most assuredly know of more. I wish somebody would indicate one to me. But, if I had called man an ape, or vice versa, I would have fallen under the ban of all ecclesiastics. It may be that as a naturalist I ought to have done so.”

• thought other apes were so similar to us but ppl didn’t like it

Linnean Taxonomy

• now more comfortable to put great apes back in our family

Jean Pierre Antoine de Monet de Lamark

• “Lamarck was the first man whose conclusions on the subject excited much attention. This justly celebrated naturalist first published his views in 1801…he first did the eminent service of arousing attention to the probability of all changes in the organic, as well as in the inorganic world, being the result of law, & not of miraculous interposition.”

• studied life in frame

• wondered if there were ordered laws for how animals change

• not changed bc of God

• due to natural phenomenon, not bc of God

• found principles in other practices (i.e., astrology), thought why not biology

Lamarkinsim & inheritance of Acquired Traits

• Lamark believed in two major causes of species change (lets consider that species aren’t static):

1. Tendency for each speciies to progress to a “higher” form

2. inheritance of acquired characteristics (happens within lifespan of organism)

   1. “…a more frequent & continuous use of any organ gradually strengthens, develops & enlarges that organ (giving) it a power proportional to (it’s) use; disuse…imperceptibly weakens (it) until it finally disappears.”

   2. “…(such) acquisitions or losses…are preserved by reproduction to the new individuals which arrise..”

Similarities in Organisms: Morphology

• When looking at bones, we all have similar parts (bones)

How Darwin got on the “Beagle”:

• Erasmus Darwin (grandfarther): leading intellectual in 18th Century England (physician, poet, & naturalist); formulated an early, formal theory on evolution in Zoonomia or the laws of organic life

• In 1827, Darwin’s father enrolls Charles into University fo Cambridge’s B.A. in theology program to quality as a clergyman

  • many English ‘naturalists’ were clergyman, exploring the wonders of God’s creation

• After graduating Cambridge, Darwin learned of a job as a captain’s assistant on the HMS Beagle whose mission was the map the coastline of South America for the British Navy

  • his dad said no, thought it would be a waste of time → but eventually agreed

Voyage of the Beagle: Map

took 5 years

The Voyage’s Impact on Darwin

• original voyage supposed to be 2 yrs, but lasted 5 yrs

• Influences on Darwin’s thinking…

  • Geologist Lyell asked the captain to record geological observations

    • captain gave this task to Darwin along w/ copy of Lyell’s book “Principles of Geology”

      • Lyell discusses graudal process taing place over extremely long periods of time

• Darwin reads Malthus “An Essay on the Principle of Population”, which stated that organisms exist in greater numbers than can survive/reproduce

  • organisms “struggle for individual survival & reproduction

  • the winners? those that are better adapted to environment

Darwin’s Finches

• Darwin collected samples of different species (insects, birds, etc.) from many areas, e.g., each Galapagos island had different local conditions & species

  • ex: saw differences in beak size but were all the same type of bird

On the Origin of Species

• Darwin wanted to explain change in species over time…

• but the big questions were:

  • how do new species emerge? & what makes them seem so well adapted to their particular environment?

• In 1859, Darwin published his landmark book, “On the Origin of Species”

• This was the culmination of 25 yrs of observation, experiment, & study across many disciplines (geography, biology, etc)

On the Origin of Species: The Tree of Life

• species do not “turn into” others, but they may share common ancestors, e.g., Last Common Ancestor (LCA

Natural Selection: 3 Components

• variation: there is remarkable variation in animal forms (e.g., body size, mass, intelligence, aggressiveness, etc.)

• selection: organisms that have traits that help them survive & reproduce will have more offspring because of their advantage over organisms w/o such traits

• heredity/inheritance: only some variation are passed on reliably to offspring

• genetic variation + differential production = evolutionary changes at genetic level (shifting allele frequency in the species population)

Cultural & Social Reactions

• ppl were offended by his findings

• that humans and monkeys/ape were related