alive
Explanation
The Joke
A bearded man (resembling a biblical figure, likely Adam) enthusiastically tells someone, "Did you know that more people are alive today than have ever died?" The caption below reads: "The Garden of Eden was a great place for demographic fun facts."
The joke is that this statement, which is a commonly cited (and actually debunked) demographic claim in the modern world, would have been trivially and literally true in the Garden of Eden. If Adam and Eve were the first two humans and neither had yet died, then 100% of all humans who had ever existed were alive -- making the "fun fact" a completely obvious and unremarkable observation rather than a surprising statistic.
The Humor
The humor comes from the incongruity of someone excitedly sharing a "fun fact" that is, in context, the most obvious statement imaginable. In the modern world, the claim that "more people are alive than have ever died" sounds impressive (even though it is actually false -- demographers estimate roughly 100 billion humans have ever lived). But in the Garden of Eden with a total human population of two and zero deaths, it is a tautology. The comic pokes fun at people who share impressive-sounding statistics without considering whether those statistics are meaningful in context.
References
The demographic claim referenced here -- that more people are alive today than have ever died -- is a persistent urban legend. The Population Reference Bureau has estimated that approximately 108 billion people have been born throughout human history, making the current population of roughly 8 billion a small fraction of all humans who have ever lived.