There are several ways to address this question, to properly answer it. Here are my thoughts...
You ask, since recorded civilization...The earliest records that have survived, are from Egyptian hieroglyphs dating to about 5500 years ago...
The earliest "true" civilizations (pepole living together in cities, or at least farming societies) is not much more than 10,000 years ago..
From 10,000 to 5,000 years ago, the total human population jumped from from 5 million to 100 million...
However 'Homo Sapiens' which are genetically identical to us, have been found by archeologists dating to almost 200,000 years ago...
So when statisticians estimate the total human population that ever lived (from "cavemen" to civilized ones), the figure is between 80-105 Billion people...6.25 Billion of which are walking the planet right now!
The first time there were 1 Billion humans on the earth was 1804...