Civilization is about 12000, earth about 4.54 billion years old. 12000/4540000000 is about 2.65*10^-6 or about 0,000265 %. If you compressed the entire existence of our planet
Blanketing much of the northern third of the African Continent, or some 3.5 million square miles, the Sahara Desert extends eastward from the Atlantic Ocean some 3,000 miles to the Nile River and the Red Sea, and southward from the Atlas Mountains of Morocco and the Mediterranean shores more than 1,000 miles to the savannah called the Sahel.
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