A rare half-male, half-female butterfly — and other photos of evolutionary wonders
The genetic mutations leading to gynandromorphy — the possession of male and female sexual characteristics by a single individual — occur throughout nature, appearing in crustaceans, birds and other animals. It is especially noticeable in butterflies (such as this birdwing, Trogonoptera trojana), because many butterfly species already show sexual dimorphism — visible differences between male and female. This birdwing shows one bright “male” wing and one duller “female.” Recently, a gynandromorphic great Mormon butterfly made headlines after emerging from a chrysalis during a 2011 butterfly show at the Natural History Museum in London. (Robert Clark/Courtesy of Phaidon)
When Charles Darwin examined an orchid from Madagascar with a nearly foot-long nectary, he was certain that a corresponding moth, one with an exceptionally long proboscis must exist. More than two decades after Darwin died, a moth matching this specification was identified. And more than 80 years after that, it was further confirmed: The Xanthopan morganii was documented feeding on this exact flower.
This moth is one of the fascinating examples of the extraordinary ways in which plants and animals have adapted elegant solutions for survival, collected in photographer Robert Clark’s new work, “Evolution” (Phaidon) with text by Joseph Wallace. Clark wholeheartedly embraces the idea that examples of evolution are all around us, if you just know where to look.
“I was never more interested in any subject in all my life than this of Orchids,” Charles Darwin wrote to his friend the botanist Joseph Hooker. Darwin’s most famous connection to these diverse and widespread plants involved Angraecum sesquipedale (now commonly known as Darwin’s orchid), a species from Madagascar. Studying it, Darwin understood that the species could be pollinated only by a moth with a proboscis far longer than any yet seen on Earth. A variety of “experts” ridiculed Darwin’s prediction, published in 1862, that such a moth must exist somewhere on Madagascar. (Ridicule was an experience he must have been used to by then.) It wasn’t until 1903 that collectors found the exact moth that he’d said was out there: Xanthopan morganii, originally given the subspecies name praedicta in recognition of the great man who predicted its existence. (Robert Clark/Courtesy of Phaidon)
Alfred Russel collected these pittas on Borneo and Sumatra, islands that lie west of what is still called the “Wallace Line.” Wallace was struck by the fact that mainly Asian fauna are found to the west of the line and Australian to the east, making the region a prime exhibit of how geographic isolation can lead to the evolution of new species. (Robert Clark/Courtesy of Phaidon)
The physical changes wrought by artificial (or domestic) selection in the pigeons Charles Darwin bred included feathers that grew up instead of down (as in the Jacobin, right) and overlarge crops (the pouter pigeon, left). (Robert Clark/Courtesy of Phaidon)
Not so long ago, it was a controversial theory, but now it’s widely accepted: Birds aren’t just dinosaur-like; they are in fact living dinosaurs. That’s true of everything from sparrows to eagles to Darwin’s finches — but it’s rarely more obvious than when looking at a southern cassowary (Casuarius casuarius), the flightless bird native to Australia and New Guinea that at 5 feet tall and over 100 pounds is one of the largest and heaviest birds on Earth. (Robert Clark/Courtesy of Phaidon)
Crocodile eyes have evolved an assortment of specializations that make them suited to the animals’ semi-aquatic environment, choice of prey and hunting technique. The eyes are protected with a third eyelid, a membrane that slides across when the reptile submerges, while the eyeballs themselves can be drawn into the eye sockets during an attack. Meanwhile, a thin layer of guanine crystals (called the retinal tapetum) lies just behind the eyes. By reflecting light back through the retina, it intensifies the image, aiding crocodiles as they hunt in low-light situations. (Robert Clark/Courtesy of Phaidon)
According to the scale of typical evolution, most dog breeds have been in existence for only an eyeblink of time. But by the standards of human history, many are practically ancient, demonstrating both the longevity and the tightness of the bond between humans and canines. For example, the Afghan hound, though having a less well-defined past, has a centuries-long history in Afghanistan and surrounding areas. (Robert Clark/Courtesy of Phaidon)
A fetus of a donkey exhibits many of the features that distinguish the family Equidae, which also includes horses and zebras.
Astonishingly, scientists recently found a powerful tool to help untangle the complex evolutionary history of the family: a 700,000-year-old colt leg bone that had been frozen in the tundra of Canada’s Yukon Territory. The bone’s excellent condition allowed scientists to map the ancient horse’s entire genome. (It remains by far the oldest DNA yet sequenced.) Among the researchers’ many findings from this scientific trove: Horses, donkeys and zebras appear to have evolved from a common ancestor 4 million to 4.5 million years ago, or twice as long ago as previously thought. (Robert Clark/Courtesy of Phaidon)
In Charles Darwin’s time, widespread excavation for mines, farms and roads revealed something crucial: that neither the kinds of organisms that inhabit the earth, nor even the planet itself, remains static. One spectacular proof of this was provided by the discovery of the Western Interior Seaway, a vast, shallow ocean that in the Cretaceous Period ranged from what is now eastern Mexico all the way to northern Canada. How do paleontologists know that this area, mostly now far removed from any marine environment, had once been a sea? Because they found fossils belonging to the huge marine reptiles called the plesiosaurs and mosasaurs there, along with gigantic sharks, other fish and crinoids (echinoderm relatives of sea urchins and sea stars) such as this beautiful specimen of Uintacrinus socialis from Kansas. (Robert Clark/Courtesy of Phaidon)
“The combination of good sedimentary conditions and the fact that animals, including hominids, like to be near a source of water,” the great paleoanthropologist Richard Leakey said, helps explain why the remains of human ancestors — and many other creatures — are so often found near the shores of lakes. These beautiful human footprints, about 120,000 years old, were discovered south of Lake Natron, Tanzania. (Robert Clark/Courtesy of Phaidon)
The skeletons of an orangutan and a giraffe demonstrate the breadth of mammalian evolution. Orangutans were one of the species that drew Alfred Russel Wallace to the forests of Sarawak on the island of Borneo, where he developed his theory of evolution. And Charles Darwin wrote extensively about the giraffe, whose long neck — well adapted to treetop browsing — he considered a striking illustration of natural selection. (Robert Clark/Courtesy of Phaidon)