Adventures in Evolution

• http://www.youtube.com/watch?v=vmphlbRhLu8

HMS Beagle

• Darwin did a 5-year voyage on the HMS Beagle

• Darwin stated “ the voyage of the Beagle has been by far the most important event in my life and has determined my whole career”

Did Darwin invent the idea of evolution?

• NO. But he is considered the father of evolution.– In 1830s people assumed that species were fixed and

unchanging– Explorers and naturalists were discovery various

plants and animals– Fossils were providing evidence of some species that

lived in the past– Anatomists noticed physical resemblances between

different species

Old ideas to explain how species changed were flawed

• Lamarckianism, named after Jean-Baptiste Lamarck– Suggested that species could change through

inheritance of acquired characteristics. – Giraffes developed their long neck by continually

stretching them to feed on tall giraffes. – Once acquired, a giraffe could then pass on trait to

its offspring

Charles Lyell

• Darwin read the work by geologist Charles Lyell, “Principles of Geology” 1833.– Book argued that earth was much older than the

6,000 years – Incremental forces operating over a vast expanse

of time

Darwin’s Voyage

• Ideas of evolution really started when Darwin unearthed a complete fossil of a giant sloth embedded in a cliff, below a layer of seashells– Animal lived in the area before it was an ocean

environment and had lived long time ago– No living animal in present day looked like the creature

found. Where had they gone?– Reasoned that when the landscape changed the animals

had been unable to adapt and became extinct.– Noticed that South American species resembled European

ones, despite different environments

Darwin’s voyage

• He evidence did not support a species perfectly adapted to its environment.

• Galapagos Islands, observed small birds, finch• He realized that the birds were all closely

related species of finch. – different size and shape of beak.

• When he returned he read the a book by Thomas Malthus that described how hunger, starvation, and disease would ultimately limit human population growth (1798)– Limitation would lead to competition for resources– Favorable variations would be preserved and

unfavorable ones destroyed– Competition, reproductive success would lead to a

species becoming more adaptive to environment.

Natural Selection

• Darwin’s original contribution to the theory of evolution he called descent with modification.

• The mechanism of evolution is natural selection.

• In 1844, Darwin developed his ideas into a 200 page manuscript

Alfred Wallace’s Thought• Wallace was also fascinated by natural history and adventure.

– Was he rich?• He traveled to Brazil, to mouth of Amazon River

– He also noticed different species of sloth monkey and other species.– What happened to his notes?

• Wallace was able to write an article about new species but it did not mention a mechanism. – What happened to him next?– He worked out a mechanism of evolution and sent the paper to

whom?

Darwin’s Book

• Wallace stimulated Darwin to finish his book• Darwin finished his book on Evolution.– “On the Origin of Species by Means of Natural

Selection” published in 1859