If the history of the Earth were compressed into a single 24 hour day, the formation of the planet took place at 12:00 midnight. The first rocks didn’t solidify in the ancient crust of the Earth until about 2:45 or 3:00 am. This first prokaryotes came into being at somewhere between 3:15 and 4:00 in the morning. Oxygen accumulated in the atmosphere more than 8 hours later, by about 12:30 pm. The first eukaryotes appears shortly thereafter, at between 1:30 and 2:30 pm. The first multicellular organisms didn’t appear until much later, at between 6 and 6:30 pm and the first animals didn’t make their appearance until about 6:30 or 7:00 pm. The invasion of solid ground didn’t take place until late in the day, at about 9:45 pm. Mammals and dinosaurs made their appearance at between 10:45 and 11:00 pm, but the dinosaurs suddenly went extinct shortly after the first flowers bloomed, at about 11:30 pm. Finally, our direct ancestors made their debut toward the end of the day at 11:59 and 40 seconds! That’s right, humans have only been walking the Earth for the last “20 seconds” of the whole “day” of Earth’s history!

There is 1000 million in a billion so 65 million is approximately 2/3 of a billion.

I’M WAY OUT ON A LIMB HERE, THIS AMOUNT IS TREACHEROUS UNLESS YOU EXCELL IN ANY OF THE MATHS.

4.5 BILLION / 3= 1.5 BILLION

OR 1/3 OF 24 HRS= 8 HRS into the 24.

….8/24

Someone like my granddaughter who teaches calculus in high school needs to answer this.

I made a stab at it!

Dinosaurs as a group got bigger over time until an extinction event 65 million years ago wiped out all but bird-like dinosaurs. Scientists don’t agree entirely on what happened, but the extinction likely was a double or triple whammy involving an asteroid impact, choking chemicals from erupting volcanoes, climate change and possibly other factors.

http://www.livescience.com/animals/051201_dinosaur_history.html

(4.4 / 4.5) x 24 = 23.46, or 23:28

Proto-humans appeared roughly a million years ago. Their appearance would have been at

(4.499 / 4.5) x 24 = 23.9947 or 23:59:41, or 19 seconds before midnight.