How many hominids have lived?

I'd read some years ago that about 100 billion homo sapiens have lived, including those 3 billion of us who were alive at that time (late 1960's or early 1970's). I am wondering how much validity such speculations may have, and if modern research (and speculation) has refined this estimate. Thanks! I hope someone will be able to contribute to answering this interesting question.

The link below seems to substantiate that view.