not op but i think your skepticism is justified

this seems to be where the image originally came from. the author explains the challenges with making speculations about historical populations in that post. the demographers, toshiko kaneda and carl haub, estimated 117 billion people have lived over the last 200,000 years. here's the explanation given on the original post:

The majority of them lived very short lives: about one in two children died in the past. When conditions are so very poor and children die so quickly then the birth rate has to be extremely high to keep humanity alive; Kaneda and Haub assume a birth rate of 80 births per 1000 people per year for most of humanity’s history (up to the year 1 CE). That is a rate of births that is about 8-times higher than in a typical high-income country and more than twice as high as in the poorest countries today (see the map). The past was a very different place.

i think this is fairly reasonable, but original source is necessary. i think this is a more original source, and kaneda and haub are listed as the authors. their methodology seems to rely a lot on guessing, which makes sense. the 117 billion is probably not entirely accurate, but i'd say it's a good attempt at estimating given what we know. there might be a more detailed paper somewhere but i didn't really look too hard

edit: also lot of hostility from other people here.. lemmy gone downhill. i think there's nothing wrong with being skeptical of data or science, even if it's coming from qualified experts. unless there's a detailed paper that explains EVERY step of their process, you can't be entirely sure where their numbers are coming from. that said, i agree with those other guys that there's not a lot of room to be skeptical in this particular case, since the authors explicitly say it's a rough estimate. based on what we know, it's as accurate as we can get. but still, nothing wrong with asking for sources!