Darwin’s Dangerous Idea The Struggle for Existence, Natural Selection & Descent With Modification

Who Was Charles Darwin? Born in 1809 to a wealthy English family Born in 1809 to a wealthy English family A below-average student at school A below-average student at school Trained as a doctor, but dropped-out Trained as a doctor, but dropped-out Trained eventually as a country clergyman Trained eventually as a country clergyman Loved travel & the outdoors Loved travel & the outdoors –“You care for nothing but shooting, dogs and rat-catching, and you will be a disgrace to yourself and all your family!” (Darwin’s dad!)

Darwin’s Travels In 1831, aged 22, Darwin was invited to join a 5yr round-the-world expedition as an unpaid naturalist on HMS Beagle In 1831, aged 22, Darwin was invited to join a 5yr round-the-world expedition as an unpaid naturalist on HMS Beagle “Woe unto ye, beetles of South America…”

The Galapagos Islands Darwin was amazed that any wildlife had reached such a remote place, and suspected that the ALL the birds, plants and animals had arrived during the past from the mainland

Galapagos Wildlife Tortoises: each island, and even specific mountains within an island, had a tortoise with a unique shell shape. Were they all descended from one ancestral tortoise? Finches: every island had a variety of finches, each with different size beaks, adapted to eating different sized seeds. One type was usually more common on each island. Were they all descended from one ancestral finch?

Darwin’s Idea In the same way that dog-breeders and farmers “altered” the appearance of animals by careful breeding (Artificial Selection), Darwin proposed that there was also a NATURAL mechanism which accomplished the same thing in nature…

The Origin of Species Darwin knew that his ideas were controversial: most scientists of the day believed that each organism was “specially created” and “fixed” in its form. He was very reluctant to publicize his ideas. Darwin knew that his ideas were controversial: most scientists of the day believed that each organism was “specially created” and “fixed” in its form. He was very reluctant to publicize his ideas. In 1858, after reading about Wallace’s research in the Malay Archipelago, Darwin decided to “go public” with his dangerous idea In 1858, after reading about Wallace’s research in the Malay Archipelago, Darwin decided to “go public” with his dangerous idea In 1859, Darwin published his ideas in a book called “On the Origin of Species by means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life” In 1859, Darwin published his ideas in a book called “On the Origin of Species by means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life”

5 Points of Darwin’s Theory Individual organisms differ, and some of this variation is heritable (offspring tend to look similar to their parents) Individual organisms differ, and some of this variation is heritable (offspring tend to look similar to their parents) Organisms produce more offspring than can survive, and many survivors do not reproduce Organisms produce more offspring than can survive, and many survivors do not reproduce Because more organisms are produced than can survive, they compete for resources (“Struggle for Existence”) Because more organisms are produced than can survive, they compete for resources (“Struggle for Existence”) Individuals best-suited to their environment survive (“Survival of the Fittest”) and reproduce most successfully. These individuals then pass on their heritable traits to their offspring (“Natural Selection”). Individuals best-suited to their environment survive (“Survival of the Fittest”) and reproduce most successfully. These individuals then pass on their heritable traits to their offspring (“Natural Selection”). ALL species alive today are therefore “descended with modification” from ancestral species that lived in the distant past. This process unites ALL organisms on Earth into a single tree of life. ALL species alive today are therefore “descended with modification” from ancestral species that lived in the distant past. This process unites ALL organisms on Earth into a single tree of life. Darwin’s original ideas on how organisms might have descended from each other

The Public Reaction Many scientists were appalled at the idea of humans evolving from ancestral apes. A fierce debate ensued. Many scientists were appalled at the idea of humans evolving from ancestral apes. A fierce debate ensued. Research in geology, paleontology, biogeography and breeding continued, as scientists sought to either confirm or reject Darwin’s hypotheses Research in geology, paleontology, biogeography and breeding continued, as scientists sought to either confirm or reject Darwin’s hypotheses

Darwin’s Legacy “There is a grandeur in this view of life,…that…from so simple a beginning, endless forms so beautiful and wonderful have been and are being evolved” “There is a grandeur in this view of life,…that…from so simple a beginning, endless forms so beautiful and wonderful have been and are being evolved” This belief has fuelled research on every continent for over 100 years… This belief has fuelled research on every continent for over 100 years…