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Get the facts behind the frame in this online-only gallery. Pick an image and see the photographer’s technical notes.
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By Rick Gore Photographs by Robert Clark
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Once upon a time, a warm-blooded, milk-producing, fur-covered beast was born. Since then, mammals have conquered every habitat on Earth. This is their story—our story.
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Get a taste of what awaits you in print from this compelling excerpt.
Deep in their bones, all mammals are related. The earliest known mammals were the morganucodontids, tiny shrew-size creatures that lived in the shadows of the dinosaurs 210 million years ago. They were one of several different mammal lineages that emerged around that time. All living mammals today, including us, descend from the one line that survived. During the next 145 million years of evolution, the dominance of dinosaurs ensured that our distant mammalian ancestors remained no larger than a cat. But when a catastrophic asteroid or comet—maybe a few comets, as some scientists are now arguing—finished off the dinosaurs 65 million years ago, mammals got the most important evolutionary opportunity they would ever have. With dinosaurs gone, mammals could exploit the planet's resources themselves. Within a few million years of the impact the fossil record shows an explosion in mammalian diversity.
How did those little creatures transform into not only the hippo and the mole rat but also today's vast panorama of mammals with fur, hooves, and fangs, as well as others that swim hairless through deep oceans—or ride, like me, in a Land Rover across this grassland?
Only humans can ask that question, or hope to answer it. We are, in a sense, the ultimate mammals. To be sure, we share defining traits with the first mammals—traits that were evolving even as the morganucodontids scrambled for food among the dinosaurs: We are warm-blooded. We have specialized jaws, whose hinges came together early in our evolution to create the ear bones that let us hear better than other animals. We have complex teeth that let us grind and chew our food so that we get more nutrition out of it. We have hair. We are superb mothers whom evolution has supplied with physical adaptations—such as breasts and placental birth—that give mammalian young an important head start. We humans are among the most recent to evolve, and we use our big mammalian brains to reason and solve problems and struggle for goals beyond our basic needs. We ask about our past and wonder what it might tell us about the future.
From scratching around in the dirt to deciphering DNA—how did we get from there to here?
Get the whole story in the pages of National Geographic magazine.
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In More to Explore the National Geographic magazine team shares some of its best sources and other information. Special thanks to the Research Division.
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Benton, Michael. Vertebrate Paleontology. Blackwell Science, 2000.
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Gore, Rick. "Georgian Skull Find," National Geographic (August 2002).
Lange, Karen E. "The Evolution of Dogs: Wolf to Woof," National Geographic (January 2002), 2-11.
Chadwick, Douglas H. "Evolution of Whales," National Geographic (November 2001), 64-77.
Lange, Karen E. "Meet Kenya Man," National Geographic (October 2001), 84-9.
Keyser, André. "The Dawn of Humans: New Finds in South Africa," National Geographic (May 2000), 76-83.
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