Over the past 125,000 years, mammals on Earth have become smaller. Ten thousand years ago the average mass of a mammal was 200 pounds and today the average mass is about 15 pounds. After dinosaurs became extinct, mammals became larger and new species developed. But when ancient humans evolved, they began hunting bigger animals. Eventually, in all areas populated by humans, the size of mammals became smaller and led to extinction in many cases. Listen to hear more about the effects humans have had on the size of mammals.
Story Length: 2:34
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