I don't know of Wolfram's statistics include population
estimates of non-counted (no Census) populations or not, so it
_might_ be misleading. The pink area stops at 1750AD. But
considering that governments have been counting heads for as
long as we've had cities, it's at least accurate for as long as
we've had cities and populations willing to be counted. 1750 AD
shows the beginning of a big "jump". It also coincides with
explorations of otherwise "uncharted" lands and people's; the
exploits of travelers and[1]pop-of-world their head-counting of
"natives" likely added to the number.
So, it's more a chart of "civilizations who counted people"
rather than absolutely fact. Nevertheless, interesting. It helps
explain why a few people in ancient times had such HUGE IMPACTS
on the millenia that followed: There were fewer people.
References
Visible links
1.
http://icopiedyou.com/wp-content/uploads/2015/09/pop-of-world.jpg
