Lecture 18

Charles Darwin

Evolutionary predecessors Over the years before Darwin, many biologists attempted to solve the mystery of the

“species question.”

• Charles Robert Darwin was born in Shrewsbury, Shropshire, England on 16th Feb 1809• His father (Robert Waring Darwin) and grandfather (E. Darwin) were both doctors• His mother was Susannah Wedgewood Darwin was the daughter of a Josiah Wedgewood - founder of Wedgewood China• He had just one brother and four sisters•He attended Shrewsbury Grammar School, but preferred to hunt and collect shells and coins. He also enjoyed learning Latin and Greek.

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Darwin Family Tree

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• In 1825 he enrolled at Edinburgh University to study medicine, where he learned about taxidermy (useful later in his life)• He dropped out because he did not like the classes.• He had failed his family• In 1827 he enrolled at Cambridge University and began to study to become a clergyman• However, he preferred to collect insects!!!• It was at Cambridge that he began to appreciate the vast diversity of species• His professors were followers of Lamarck’s ideas about inheritance of acquired characters• He also learnt natural theology - Understand God by studying God’s creation

• Darwin did graduate from Cambridge at age 23 with a B.Sc. Degree in Theology• Before joining the Church of England he wanted to travel - as it was the great time of exploration.• He wanted to visit exotic locations before settling down to relegious work.

• In 1830, the British government commissioned a 90-foot ship HMS Beagle devoted to ‘the acquisition of knowledge.’ It was really to test new clocks and find new sources of wealth.• Darwin, through a contact at Cambridge, was recommended and signed up as the ship’s unpaid naturalist

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• The The BeagleBeagle sailed more than 40,000 miles from Dec 1831 to Oct 1836 sailed more than 40,000 miles from Dec 1831 to Oct 1836• Darwin spent 18 months at sea and the rest of the time on landDarwin spent 18 months at sea and the rest of the time on land• Of the 58 month voyage, he spent 43 in South AmericaOf the 58 month voyage, he spent 43 in South America• He visited the Galapagos Islands where he made his most profound He visited the Galapagos Islands where he made his most profound observations.observations.• This time would transform his life and biology!This time would transform his life and biology!

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Darwin exploring the Galápagos Islands Darwin exploring the Galápagos Islands

Galápagos tortoise Galápagos tortoise

Then back on England Darwin began to put all the pieces together….

• Whilst on the voyage he was given a book to read by the captain - this book would transform Darwin’s thinking

• The book was written by Lyell, who had put together all the previous arguments about the age of the Earth and geological time, providing real examples of geological changes that shaped the planet.

• When Darwin boarded The Beagle he was a firm believer in the clergy and the fixation of species - when he disembarked he was a changed man and wanted to discover the laws of nature!

Another book that Darwin read sealed the deal for him…

• A manuscript published by Thomas Malthus implied that given ideal conditions a population would grow exponentially• However, the resources would not grow in the same fashion - they would grow linearly• Therefore, at some time the population would exceed the resources and there would be a ‘struggle for existence’

• Darwin put together the short term struggle for existence (Malthus) with the great geological timescale (Lyell)

Galápagos finches Analysis of these finches led scientists to hypothesize that they were derived from one

ancestor arriving from the mainland to populate and diversify across the islands.

FIGURE 1.3 J-B. de Lamarck (1744—1829) (a) J-B. de Lamarck worked most of his life at the Muséum d’Histoire Naturelle (b). His

academic position gave him a chance to promote the idea that species change.

Giraffe necks Applied to giraffes, Lamarck’s view (top) would expect that stretching giraffes lengthened

their necks to reach tree-top vegetation, and this acquired characteristics was passed to offspring. In Darwin’s view (bottom), giraffes with long necks out competed those with short necks who died for want of successful resources.

Schools of evolutionary thought The views of Linneaus, Lamarch, and Darwin are contrasted. A) Linneaus saw each species

as a separate act of creation, one by one. B) Lamarck envisioned the passage of acquired characteristics of one generation to succeeding generations. C) Darwin viewed evolution as descent with modification.

FIGURE 1.2 Carolus Linnaeus (1707—1778) This Swedish biologist devised a system still used today for naming organisms. He also

firmly abided by and promoted the view that species do not change.