Time
How long have humans existed, on a 24-hour Earth clock?
If Earth's 4.54 billion years were compressed into 24 hours, Homo sapiens (about 300,000 years old) would show up in the last 6 seconds.
Source: Dalrymple (2001); Hublin et al. (2017), Nature.
Context
Earth is about 4.54 billion years old and anatomically modern humans appear about 300,000 years ago. Divide one by the other and our species occupies about the last 6 seconds of a 24-hour day.
The 300,000-year figure comes from the Jebel Irhoud fossils in Morocco, dated by Hublin and colleagues in 2017. Before that paper the usual figure was lower, which would have made our slot on the clock even shorter.
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