Darwin found the barren, windswept Falkland Islands "desolate and wretched." Little grew there except "withered grass" and "a few very small shrubs." But Darwin perked up when he cracked some "primitive looking rocks" with his hammer and found fossils. The Falklands were full of brachiopods--two-shelled animals that were once among the most abundant species on Earth. Excited about finding these clues to life in the distant past, Darwin wrote to Henslow describing his "high good fortune."
Links to the Past
With 35,000 species living at different times over the past 570 million years, brachiopods are excellent for dating the rocks they are found in: Since rocks from different eras contain their characteristic species of brachiopods, one can determine the age of a rock layer by the type of brachiopod fossils found in it. Modern dating methods confirm the accuracy of this technique.
"I think the comparison of these impressions with those of the oldest fossiliferous rocks of Europe will be preeminently interesting."