Charles Darwin and The Theory of Evolution

The Evolution of a Theory

Charles Darwin

Born: February 12, 1809Died: April 19, 1882

Charles Darwin

Education: Bachelor of Arts Degree Cambridge 1831. Originally studied medicine for 2 years but discontinued. Developed a strong interest in biology and geology.

Theory not unique

The idea of life coming from non-life is not original to Darwin. However Darwin believed that instead of the environment giving rise to habits, which in turn produce new traits, Darwin maintained that something within the organism itself gives rise to new traits.

Prior to Darwin: Body Structure Responds to Needs/Habitat

Darwin: Something Within Responds

Darwin Was on the Right Track…However He Did Not Know What it Was!

1831—British Mapping Expedition. HMS Beagle

• 90 feet long, crew of 74, 5 year voyage

Darwin’s Voyage

Darwin’s Data

On returning to England, Darwin and an ornithologist associate identified 13 species of finches that he had collected on the Galápagos Islands. This was puzzling since he knew of only one species of this bird on the mainland of South America, nearly 600 miles to the east, where they had all presumably originated. He observed that the Galápagos species differed from each other in beak size and shape. He also noted that the beak varieties were associated with diets based on different foods. He concluded that when the original South American finches reached the islands, they dispersed to different environments where they had to adapt to different conditions. Over many generations, they changed anatomically in ways that allowed them to get enough food and survive to reproduce. This observation was verified by intensive field research in the last quarter of the 20th century

Darwin observed and identified

• Adaptation and Natural Selection

Galapagos

Darwin’s Data

Variation in Finch Beaks

Darwin’s Data

• Darwin came to understand that any population consists of individuals that are all slightly different from one another. Those individuals having a variation that gives them an advantage in staying alive long enough to successfully reproduce are the ones that pass on their traits more frequently to the next generation. Subsequently, their traits become more common and the population changes.

Darwin’s Interpretation

Darwin’s interpretation

• Darwin made accurate observations. He observed animals adapting to their environment.

• He saw changes in beak shapes• He realized that the birds with beaks best

suited for survival were “selected.” He noticed that they were able to pass on those beaks to the next generation—Natural Selection!

Variation From One Parent..All Finches

Darwin’s Book

In 1859 Darwin published a book: The Origin of Species by Means of Natural Selection: The Preservation of Favored Races in the Struggle for Life

Darwin’s Basic Premise

The first life (single-celled) originated by undirected natural forces. From this single cell all other life developed via adaptation and natural selection. Over time, small changes add up to big changes

Darwin’s Idea Had Appeal

• Darwin’s premise of naturalism appealed to those looking for alternatives to the biblical creation model.

• This occurred despite the law of biogenesis as postulated by Luis Pasteur—Life only originates from life and does not spontaneously generate itself. Omne vivum ex vivo, Latin for "all life [is] from life".[

Darwin’s Tree of Life

Great Unknowns!

1. In Darwin’s day no one understood the concept of inheritance (how traits are passed on to offspring)

2. In Darwin’s day DNA (genes) had not been discovered

3. Darwin simply observed variation in a species and assumed little changes would eventually add up to large changes

Gregor Mendell

• Born: July 20, 1822• Died: January 6, 1884

Considered the father of modern Genetics. Did extensive experiments with pea plants. Proved that traits are inherited from parents.

Gregor Mendell

*Discovered that a trait could appear in one generation, then disappear in the next, then reappear again!

*Reasoned that there must be “particles” that are responsible for traits being expressed.

*Mendell was right! These “particles” were later discovered to be genes!

Watson and Crick

Watson and Crick 1953

• Discovered that DNA is the code of life…a super language capable of storing an immense amount of information.

• Darwin was correct-the cause of an organism's response to its environment lies inside the organism…not out.

• The mechanism of Mendel's inheritance experiments are identified!

Crick’s Response

• Crick has refined this idea to directed panspermia. To overcome the huge hurdles of evolution of life from non-living chemicals on earth, Crick proposed, in a book called Life Itself, that some form of primordial life was shipped to the earth billions of years ago in spaceships—by supposedly ‘more evolved’ (therefore advanced) alien beings.4

Crick’s Response

• Crick later acknowledged the mounting problems and futility of his ideas when he was reported as saying, ‘Every time I write a paper on the origin of life, I swear I will never write another one, because there is too much speculation running after too few facts … .’ 3

1953

• Watson and Crick showed that each strand of the DNA molecule was a template for the other. During cell division the two strands separate and on each strand a new "other half" is built, just like the one before. This way DNA can reproduce itself without changing its structure -- except for occasional errors, or mutations.