DARWIN’S VOYAGE ABOARD THE BEAGLE

1831 - 1836

DARWIN’S INFLUENCES:

LINNAEUS

HUTTON

The theory that changes in the earth's crust during geological history have resulted from the action of continuous and uniform processes.

LYELL

MALTHUS

ADAM SMITH

No society can surely be flourishing and happy, of which the far greater part of the members are poor and miserable.

To feel much for others and little for ourselves; to restrain our selfishness and exercise our benevolent affections, constitute the perfection of human nature.

Science is the great antidote

to the poison of

enthusiasm and

superstition.

Darwin's Discovery:

It was on Santiago that Darwin made his first curious discovery. He found a horizontal white band of shells within a cliff face along the shoreline of Porto Praya. The fact that this layer was forty-five feet above sea level raised some interesting questions for Darwin.

- It was obvious that this layer of shells was at one time under the ocean. How did it end up forty-five feet above sea level?

- Was it possible that small upward movements of the land raised the shell layer? More violent movements of the earth would have otherwise broken up the nearly horizontal line of shells.

The arrangement of the shell layer appeared to support Lyell's theory of a world slowly changing over great periods of time, a novel concept in Darwin's day. This observation, and many others like it, would later lead Darwin to develop his own theory of raising continents and sinking ocean floors.

"We had several quarrels; for when out of temper he [FitzRoy] was utterly unreasonable. For instance, early in the voyage at Bahia in Brazil he defended and praised slavery, which I abominated, and told me that he just visited a great slave-owner, who had called up many of his slaves and asked them whether they were happy, and whether they wished to be free, and all answered 'No.' I then asked him, perhaps with a sneer, whether he thought that the answers of slaves in the presence of their master was worth anything. This made him excessively angry ..."-- Charles Darwin [11]

Darwin's Discovery:

Darwin went on shore and spent the next few weeks engaged in fossil collecting. One thing that caught Darwin's attention was how different the fossils on the island were from those he found on the coast of South America. During his stay at the Falklands Darwin decided to do comparative studies between all the fossils, plants and animals he collected during the voyage. Such studies would later influence his views on plant and animal distribution, and eventually on the adaptation of similar species to different environments.

Darwin's Discovery:

While searching for fossils along the shore of Punta Alta, Darwin came across a very interesting find. He uncovered the complete fossil of a very large animal which he could not identify at all (it turned out to be a giant ground sloth). What struck Darwin as very odd was that this fossil was imbedded in a cliff face below a layer of white sea shells, similar to the layer he found on the island of Santiago the year before. Needless to say, this puzzled Darwin a great deal. Among the questions that ran through Darwin's head were:

- Why were there were no living animals in South America that looked remotely like the creature he found?

- Did changes in the environment cause its extinction? If so, why?

- If the environment did change, what caused those changes?

- How long ago did this creature die? According to Lyell's theory, land masses rose in tiny increments over eons of time. Based on where this fossil was situated, it must have died many thousands of years ago.

Darwin's Discovery:

One thing that puzzled Darwin about the fossils he was collecting throughout South America was that many of them had obviously been huge animals in their day. The problem was, large animals require huge amounts of food to survive, and this area of South America had very sparse vegetation. Darwin theorized that during the time these huge animals roamed the continent the plains must have been covered in lush vegetation. Perhaps over time the vegetation became more sparse and the animals starved to death?

The obvious question was - what caused the environment to change so dramatically?

Darwin had second thoughts on this, however. He saw that by comparing the large size of modern animals in Africa, a region with sparse vegetation, to the fossils he was collecting in South America, that the bulk of an animal has no relation to the amount of food it needed to consume each day.

Therefore, an environmental change that reduced the vegetation in South America may not have caused the animals to die off.

The burning question remained - how did the animals become extinct?

Darwin's Discovery:

While on this trek Darwin spent much time thinking about how species in South America were similar to those in Europe. He found it odd that within such different environments there existed the same types of animals. This conflicted with the notion that god created each species perfectly adapted to its particular environment.

Darwin's Discovery:

Darwin was very curious about the geology of the river valley. The walls of the valley had the same layers of shells he had seen many times before. It was during this expedition that Darwin theorized that the cliffs of the river valley, and indeed the Andes Mountains themselves, had been slowly raising above sea level.

The evidence for a planet in a state of constant flux was becoming stronger and stronger. While today we take this for granted, in Darwin's day the notion of changes on a planetary scale went against the view that god's creation was perfect and thus change was unnecessary.

Darwin's Discovery:

On March 4th the Beagle entered the Harbor of Talcuhano near Concepcion. As at Valdivia, nearly every house around the harbor was destroyed. While the Beagle tried to make anchorage in Talcuhano Harbor, Darwin was dropped off at the island of Quiriquina. Here he explored around the coastline of the island and found several expanses of fresh marine rock that had risen a few feet above sea level due to the earthquake. Darwin also noticed raised shell beds on the cliffs above and became very excited about this find, as it was direct evidence that the Andes mountains, and indeed all of South America, may be very slowly raising above the ocean. These discoveries added much weight to Charles Lyell's theory that land masses rose up in tiny increments over extremely long periods of time. Given this fact, Darwin accepted the idea that the earth must be extremely old. The next day Darwin went by ship to Talcuhano Harbor where a tidal wave had destroyed nearly everything, and from the shore he rode by horse to the town of Concepcion to meet up with Capt. FitzRoy.

Darwin's Discovery:

Darwin head back, on March 29th, to Chile via the Uspallata Pass, just north of Mendoza. He spent the next few days at Villa Vicencio and explored the geology of the area. He was shocked to find that the local mountains were mainly composed of submarine lava flows, and these at 6,000 feet above sea level and 700 miles from the coastline! Eleven trees had been fossilized and 30-40 had turned into calcareous spar. Most of the trees were a few feet tall and snapped off at the top and 3-5 feet in circumference, and were coniferous. To make matters even more confusing for Darwin, he also found huge numbers of petrified trees in the same area. His mind was reeling with questions: how long ago was this land under the ocean, how did the trees end up under water so they would become petrified? Darwin spent the next few days thinking about how Charles Lyell would interpret what he was seeing and also began developing some geological theories of his own.

"I industriously collected all the animals, plants, insects & reptiles from this Island. [on Charles Island] It will be very interesting to find from future comparison to what district or 'center of creation' the organized beings of this archipelago must be attached." Charles Darwin's Beagle Diary, September 26/27, 1835.

"Seeing this gradation and diversity of structure in one small, intimately related group of birds, one might really fancy that from an original paucity of birds in this archipelago, one species had been taken and modified for different ends." Charles Darwin, Journal of Researches, 2 edition, page 380.

Darwin’s major books1839 – Voyage of the Beagle1851 – 1854 – Living and Fossil Cirripedia1859 – On the Origin of Species1862 – On the Various Contrivances by which British and Foreign Orchids are Fertilised by Insects1865 – On the Movements and Habits of Climbing Plants1868 – The Variation of Animals and Plants under Domestication1871 – The Descent of Man, and Selection in Relation to Sex1872 – The Expression of the Emotions in Man and Animals1875 – Insectivorous Plants1876 – The Effects of Cross and Self Fertilisation in the Vegetable Kingdom1877 – The Different Forms of Flowers on Plants of the Same Species1880 – The Power of Movement in Plants (with son Francis Darwin)1881 – The Formation of Vegetable Mould, Through the Action of Worms