A Man To Watch

Darwin was something of a scientific celebrity when he got back to England. The strange fossils and unfamiliar animals he had shipped home gained him entry into London's learned circles. Mere months after he left the Beagle, Darwin presented his first paper--on the uplift of the Andes--at the Geological Society.

Determined to earn the respect of the men he called the "great guns," Darwin threw himself into work. Sorting his Beagle specimens and arranging for experts to analyze them were his first priority. What these authorities told him about his specimens--particularly the fossils and the birds--would profoundly affect his developing theories.

Peculiar Plants
Sicyos.  ©Herbarium, University of Cambridge, UK


©Herbarium, University of Cambridge, UK

Darwin never claimed to be a botanist. "I knew no more about the plants I had collected than the Man in the Moon," he wrote his old Cambridge mentor, John Henslow--humorously overstating his ignorance, as he often did. In fact, Henslow had taught him well, and Darwin was a very systematic plant collector. He plucked, pressed and brought back to England a specimen of every species he found in flower on the Galápagos.

Darwin suspected that many of his specimens were "peculiar" to the Galápagos--that is, existed nowhere else--and he was eager for Henslow's analysis. Close study of the plants might have provided a clue that they were related to those on the mainland and that their differences were a product of geographic isolation. But Henslow was absorbed in the responsibilities of his family and his country parish--and despite Darwin's pleas, Henslow studied very few Galápagos plants.

Galapagos finches
Finches from the Galapagos Archipelago, showing beak variation

Finches from the Galapagos Archipelago, showing beak variation

Darwin's Galápagos birds told an amazing story--but it was one Darwin fully understood only when he heard it from the experts. For instance, Darwin was stunned to learn, back in London, that a group of Galpagos specimens he had thought included many different birds were actually all finches. They were just finches that looked remarkably different from one another--almost as if, he would later write, "one species had been taken and modified for different ends." And there was more news. Ornithologist James Gould told Darwin that he had brought home three entirely new species of mockingbird, two of the three confined to different islands.

Darwin quickly saw what this meant for evolution. Did islands--and isolation--somehow give rise to new species? Had all these diverse-looking finches, and these species of mockingbirds, diversified from South American ancestors? Darwin hadn't kept track of where he collected each finch, so although he hastily got finches from other Beagle crewmembers and gave them to Gould, the finch evidence remained shaky. Still, the birds were part of an evolutionary puzzle beginning to fall into place.

Darwin Wonders About Finches
Lesser rhea (Rhea darwinii).  Illustration by John Gould, from Zoology of the voyage of H.M.S. Beagle ©AMNH Library

Lesser rhea (Rhea darwinii). 

Illustration by John Gould, from Zoology of the voyage of H.M.S. Beagle ©AMNH Library

These Galápagos birds show a wide range of beak shape and size, but--as Darwin was surprised to learn from bird expert John Gould--they are all finches. Seeing this kind of variation among birds of the same kind made Darwin question the idea that species are fixed and unchanging. These engravings, by John Gould, appeared in the second edition of Darwin's Journal of Researches.

Darwin Wonders About Rheas

Bird expert John Gould named this rare South American ostrich Rhea darwinii in honor of its collector. (Gould was evidently unaware the bird already had a name--Rhea pennata.) Gould's confirmation that this was indeed a distinct species fueled the fire of Darwin's curiosity. Darwin knew a larger rhea was common in an adjacent region: Were the two derived from a common ancestor?

Strange Beasts
Toxodon skull

Toxodon skull

This skull--which belongs to an enormous extinct mammal called Toxodon--was one of the many spectacular fossils Darwin sent home from South America. Some boys in a remote village in Uruguay had used the skull for target practice and knocked a tooth out with a stone. Darwin bought it from them and was pleased to find a "perfect tooth, which exactly fitted one of the sockets in this skull," 200 miles away.

This particular animal belongs to a group without modern descendants, but many of Darwin's fossils seemed to be huge variants of the same general kind of animal he had seen roaming the landscape during his explorations. This led him to wonder if the fossils might be evidence of ancestral forms. In later years Darwin would write that the South American fossils were essential to the "origin of all my views."

Toxodon platensis skull

Toxodon platensis skull

Darwin Wonders About Fossils

Paleontologist Richard Owen analyzed the fossil mammals from the Beagle voyage. This lithograph of the Toxodon skull by artist George Scharf was part of the Zoology of the Voyage of H.M.S. Beagle, edited by Darwin. In it the young naturalist described the habitats and behaviors of the living species he had collected, and the localities from which his fossils had come.

This book was only part of Darwin's scientific output during the London years. He also wrote a treatise on coral reef formation and the wildly popular Journal of Researches, based on his shipboard journals.