If the entire history of the earth was relative to 1 day, how long would humans been around for?

The lowest estimate of the age of Earth is 4.5 billion years. Homo Sapiens have existed for about 200,000 years. 200,000 is 4 one-thousandths of 1 percent of 4.5 billion. 4 one-thousandths of 1 percent of 24 hours is about 3.5 seconds. So, on a 24-hour earth clock, Homo Sapiens have existed for about 3.5 seconds. Cro-Magnons (modern humans) have existed for about 35,000 years. 35,000 is 8 ten-thousandths of 1 percent of 4.5 billion. 8 ten-thousandths of 1 percent of 24 hours is about 0.7 seconds. So, on a 24-hour earth clock, Modern Man (us) has existed for less than one second. Kind of humbling, isn't it. .

The above answer is still a bit long based on a one day earth life span. Back in 1977 astronomer Carl Sagan wrote a book called "Dragons of Eden" in which he made a one year "cosmic calendar" based on the Big Bang at 15 billion years ago to now, starting at Jan 1st. It showed hominids appearing on Dec 31 at 930 PM. Cave paintings at 1159 PM. The Renaissance at 11:59:59. PM. Space exploration beginning in the first second of the next year. New discoveries since 1977 may have changed Carl Sagan's calendar a little. In any case it sure makes a person seem small and insignificant. Then consider the changes people have made to the planet in this few minutes of cosmic time and where we are heading for the future.

Do the math.