Date: 1833
Owner: D. Appleton and Company
Source Type: Images


This diagram from Darwin's Voyage of the Beagle shows the bones of a mylodon, an extinct kind of giant sloth, that Darwin excavated in Bahia Blanca. Very little paleontological work had been done in South America prior to Darwin's visit (Humboldt had done a small amount of bone collecting), so Darwin was amazed to discover how the animals in the fossil record differed significantly from those then living on the continent. For one thing, the ancient species were much larger, yet there was ample evidence that ancient and modern species had much in common, like the extinct giant sloth and the modern tree sloth. Darwin also discovered the fossils of an ancient toed horse, though it was previously thought that there was nothing resembling a horse in South America prior to the Spanish conquest.

These fossils presented many problems. What killed off all of the animals? Was creation a continuous process or had it all been done in a week? Did these species fail to board Noah's Ark before the flood? Why do they share so many characteristics with living species?
The long-extinct species of South America, just like the insular diversity found on the Galapagos Islands, were essential to the formulation of the concept of natural selection. Darwin, perhaps more famously than any other scientist, benefited from using South America as a "field" for work in the natural sciences.

CITATION:  Mylodon. Darwin, Charles. Journal of Researches into the Natural History and Geology of the Countries Visited During the Voyage Round the World of H.M.S. 'Beagle' Under the Command of Captain Fitz Roy, R.N. New York: D. Appleton and Company, 1890. pp. 140.