[...]... particularly to the Canadian geologists and paleobotanists who had already mapped them In fact, Ashton Embry, the leader of the teams that did much of this work, had described the geology of the Devonian Canadian rocks as identical in many ways to the geology of Pennsylvania’s Ted and I were ready to pack our bags the minute we read this phrase The lessons we had learned on the highways of Pennsylvania... classic monograph On the Nature of Limbs, Charles Darwin supplied an elegant explanation for it The reason the wing of a bat and the arm of a human share a common skeletal pattern is because they shared a common ancestor The same reasoning applies to human arms and bird wings, human legs and frog legs—everything that has limbs There is a major difference between Owen’s theory and that of Darwin: Darwin’s... new about the origin of land-living animals What we saw gradually emerge from these rocks during the fall of 2004 was a beautiful intermediate between fish and land-living animals Fish and land-living animals differ in many respects Fish have conical heads, whereas the earliest land-living animals have almost crocodilelike heads—flat, with the eyes on top Fish do not have necks: their shoulders are attached... used that hand to carry and caress Suddenly, this mechanical exercise, dissection, became deeply and emotionally personal Until that moment, I was blind to my connection to the cadaver I had already exposed the stomach, the gallbladder, and other organs; but what sane person forms a human connection at the sight of a gallbladder? What is it about a hand that seems quintessentially human? The answer... a few small bones in a fish like Tiktaalik Tracing arm bones from fish to humans I can do a similar analysis for the wrists, ribs, ears, and other parts of our skeleton—all these features can be traced back to a fish like this This fossil is just as much a part of our history as the African hominids, such as Australopithecus afarensis, the famous “Lucy.” Seeing Lucy, we can understand our history as... normal fish, with fins and scales, but behind its throat were large vascular sacs: lungs Yet the creature had scales and fins So confused were the discoverers that they named the creature Lepidosiren paradoxa, “paradoxically scaled amphibian.” Other fish with lungs, aptly named lungfish, were soon found in Africa and Australia African explorers brought one to Owen Scientists such as Thomas Huxley and the. .. very early creature with limbs and one of the earliest known tetrapods Then there is eastern North America, where we had already worked, home to Hynerpeton And there is a third area, large and running east–west across the Canadian Arctic There are no trees, dirt, or cities in the Arctic The chances were good that rocks of the right age and type would be extremely well exposed The Canadian Arctic exposures... attached to their heads by a series of bony plates Early land-living animals, like all their descendants, do have necks, meaning their heads can bend independently of their shoulders There are other big differences Fish have scales all over their bodies; land-living animals do not Also, importantly, fish have fins, whereas land-living animals have limbs with fingers, toes, wrists, and ankles We can... the anatomist Carl Gegenbaur found lungfish to be essentially a cross between an amphibian and a fish Locals found them delicious A seemingly trivial pattern in the fins of these fish had a profound impact on science The fins of lungfish have at their base a single bone that attaches to the shoulder To anatomists, the comparison was obvious Our upper arm has a single bone, and that single bone, the. .. like a set of jaws They were, however, unlike the jaws of any fish I had ever seen They looked as if they might have connected to a flat head One day later, my colleague Steve Gatesy was flipping rocks at the top of the quarry Steve removed a fist-size rock to reveal the snout of an animal looking right out at him Like my ice-covered fish at the bottom of the pit, it had a flat head It was new and important . between fish and land-living animals. Fish and land-living animals differ in many respects. Fish have conical heads, whereas the earliest land-living animals have almost crocodile- like heads—flat,. remnants of an ancient tropical delta, almost like the Amazon: fossilized plants and fish that could have thrived only in warm, humid locales. The presence of warm-adapted species at what today are. usually true in areas that have a straightforward, layer-cake arrangement (think the Grand Canyon). But movements of the earth’s crust can cause faults that shift the position of the layers, putting