According to the Anno Domini designation, the year is now 2014. But the Earth has been around a lot longer than that - about 4.567 billion years. The first evidence of life dates back to around 3.8 billion years ago. Homo sapiens first appeared on the planet around two hundred thousand years - or ten thousand generations - ago.
How's that for perspective?
Kirk Johnson, director of the National Museum of Natural History, calls this perspective "deep time." This is the story of our planet preserved in "the DNA of living things," Johnson explains, as well as "in the fossils we find, in the geologic structures of our planet, in the meteorites we scavenge from the ice fields in Antarctica. Those things together give us an incredible manual for thinking about the planet."
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