Dr McConeghy Classnotes

Darwin, and the Geologists

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(Note: see When Good ideas go Bad for discussion of "Social Darwinism" and its descendants, Communism, Fascism, Racism, Imperialism, Elitism, Eugenics)

All of these sites are full of information about Darwin:

• A Biography
• A Biography
• A Biography
• What kind of a person was Darwin?
• The Origin of Species The actual text of Darwin's book
• The Origin of Species Another copy of the same book
• The Descent of Man Actual text of the book Darwin wrote about how he thought humans developed. An interesting book, but obviously very out-of-date as we have learned much, much more since his time.

Darwin was from a wealthy and highly respected family in England. He was a recent college graduate when he was offered an opportunity to travel around the world in the British naval ship HMS Beagle. On this scientific expedition he saw many areas that had never before been examined by a trained biologist, particularly several isolated islands where there were unusual animals. His observations in the Galapagos Islands and elsewhere led him to an understanding of the way that modern plants and animals have developed.

The Voyage of the Beagle The actual text of Darwin's book about his voyage.

Soon after he returned home to England, he wrote a long note to himself setting out his ideas about Evolution. Then, for many years he worked quietly at home. He wrote to many other biologists and visited scientific friends, but for the most part he stayed at home with his family. Over a period of many years he continued to think about the subject of Evolution, and carried out many ingenious experiments in other aspects of biology.

Other scientists were working in the same direction as Darwin and many of them knew about Darwin's work from private conversations. They encouraged him to write about his ideas but he was very reluctant. He worked on a book, but refused to publish. Eventually, in 1858 he received a letter from a young biologist named A.R. Wallace. Wallace's letter included an explanation of Evolution which was virtually identical to what Darwin had written. Darwin realized that it was just a matter of a short time before many different biologists all came up with the same idea. He went ahead and published his book in 1859, and he also saw to it that young Wallace was honored for his ideas as well.

• The Origin of Species The actual text of Darwin's book of 1859

• The Origin of Species Another copy of the same book

• The Descent of Man Actual text of the book Darwin wrote about how he thought humans developed. An interesting book, but obviously very out-of-date as we have learned much, much more since his time.
  

The beautiful variations in these flowers remind us of the variety within a single group of individuals.

The Basic Idea of Natural Selection

Darwin's basic idea, like many great ideas in history, can be summed up in a straightforward way that can be understood by any intelligent person. It was first explained to the public in his 1859 book On the Origin of Species (see links above.)

His model for Natural Selection --the process by which evolution on Earth developed the vast variety of living things -- is based on this set of ideas:

1) populations have variability -- that is, individuals within a population are not all the same, they vary from one individual to another. This is true for essentially all populations. The variations are inheritable -- that is, tall parents tend to have tall children, etc... Sometimes mutations create an advantage or disadvantage for the individual...

2) more offspring are produced than can survive -- the number of seeds, eggs, etc produced by living things are far in excess of the number that can survive. It is obvious if you think about it, but even though a parent produced thousands of offspring, nearly all of them must die -- in fact, a typical parent can, on the average, only produce one offspring who live to maturity, or a pair of parents can only produce two offspring who survive. If this were not true, the world would be overrun. This implies that there is a battle for survival among individuals, and that only the individuals who are best fit will be able to survive.

3) individual variances (differences) may help some individuals to survive -- not all offspring can survive, so what made it possible for those who survived to beat their siblings? It may be that the ones who survive have some particular trait or characteristic which helped them to survive when their siblings were killed

4) the individuals who survive are the ones who will reproduce. Their traits will be passed down to their offspring. The traits of the survivors will become more common in the population, while the traits of the losers will die out or disappear... over a period of time, this means that the individuals who are not fit will be eliminated, and if conditions change, the population will change.

Once you have accepted the idea that the Earth is very old, and that the simple ideas above are correct, then coming to "Evolution by Natural Selection" is unavoidable. But, is the Earth old?

Is the Earth Old? Two Problems with Geology and Evolution:

Two problems with understanding Evolution were actually solved by geologists:

First, in the 1700s and even in the 1800s many people in Europe believed that the earth was only 6000 years old.  A short 6000 year period did not allow enough time for the millions of different plants and animals to develop by Evolution. (see Science Guys, Bishop Ussher for details about how this belief originated).

From about 1750 onward, geologists such as James Hutton, William Smith and Charles Lyell (see Science Guys) began to understand that the earth was much, much older than 6000 years -- it was millions or even billions of years old. The evidence for the great age of the earth was important in allowing biologists to think about how the varieties of living things could have developed. 

plants in Hawaii

Second, another problem with understanding evolution was trying to figure out why animals and plants were spread out over the earth in such unusual ways. For instance, Why were there so many marsupial animals in Australia? So few types of animals and plants in Hawaii? Such a strange assortment of birds in the Galapagos?

Curiosity about these kinds of questions led to many different investigations, including study of the movement of the continents. The work of Alfred Wegener and others in what we now call "Plate Tectonics" has given us a far better understanding of how the earth is built. And, it also is a neat confirmation of many previous observations about evolution.

It is interesting that in Darwin's book The Voyage of the Beagle, he wrote about the age of islands in the Pacific and speculated how they might have been formed. Now, nearly 200 years later, his ideas about these islands have been confirmed by very strong evidence of several kinds -- that Darwin guy, he was really smart!!!