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Evolved to Run Walking long distances is fundamental to being a hunter-gatherer, but people sometimes have to run. One powerful motivation is to sprint to a tree or some other refuge when being chased by a predator. Although you only have to run faster than the next fellow when a lion chases you, bipedal humans are comparatively slow. The world’s fastest humans can run at 37 kilometers (23 miles) per hour for about ten to twenty seconds, whereas an average lion can run at least twice as fast for approximately four minutes. Like us, early Homo must have been pathetic sprinters whose terrified dashes were too often ineffective. However, there is plentiful evidence that by the time of H. erectus our ancestors had evolved exceptional abilities to run long distances at moderate speeds in hot conditions. The adaptations underlying these abilities helped transform the human body in crucial ways and explain why humans, even amateur athletes, are among the best long-distance runners in the mammalian world. Today, humans run long distances to stay fit, commute, or just have fun, but the struggle to get meat underlies the origins of endurance running. To appreciate this inference, try to imagine what it was like for the first humans to hunt or scavenge 2 million years ago. Most carnivores kill using a combination of speed and strength. Large predators, such as lions and leopards, either chase or pounce on their prey and then dispatch it with lethal force. These dangerous carnivores can run as fast as 70 kilometers (43 miles) per hour, and they have terrifying natural weapons: daggerlike fangs, razor-sharp claws, and heavy paws to help them maim and kill. Hunters
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Daniel E. Lieberman (The Story of the Human Body: Evolution, Health and Disease)