Depending who you speak to and who calculates it, some have the great flood as early as 3300 BC.
Since we’ve double the planet’s population in 40 years, you could use that as “guide” to figure the planet “could” double the population every 40 years. In 800 years you could go from 8 people to about 8.3 million people. If you doubled every 20 years (totally possible) you end up with a number in the trillions. 800 years can be a VERY long time in population growth!
Ever wondered how we have made great technological strides in the past 500 years or so and these civilizations that were around for, supposedly, thousands of years stayed in the stone age? Maybe, just maybe, they weren’t around for as long as we thought...
We stayed at mostly the same technology level for a long time. If you grabbed Socrates from 400BC and brought him forward to 1200AD, he would not see much changed. People still plowed with animals drawing plows, rode horses for transport, and ships still used sails. The world would be very comprehensible to him. Even drawing him forward to 1750 or so, the main innovation would be gunpowder. Most other aspects of people's lives would be very similar.
Go forward just 100 years to 1850, and things get very different, with steam powered railroads and electric telegraphs. Jump forward another 100 years to 1950, and Socrates would think he was in a world of sorcery.
What created such a rapid degree of progress was an increasing number of very smart people who were allowed to innovate under the free market, and reap great rewards for innovation.
I'm mostly bowing out at this point, and letting Elendur have a turn at banging his head against the wall.