Good question. And it recalled to mind an article by Dinesh D’Souza that I read recently. Although D’Souza initially ignored this question, posed in similar fashion by atheist Christopher Hitchens during their debate, he revisits the question after considerable thought and research:
Here is the thrust of Hitchens’ point: God seems to have been napping for 98 percent of human history, finally getting his act together only for the most recent 2 percent? What kind of a bizarre God acts like this? . . . The Population Reference Bureau estimates that the number of people who have ever been born is approximately 105 billion. Of this number, about 2 percent were born in the 100,000 years before Christ came to earth. “So in a sense,” [Erik] Kreps [of the Survey Research Center of the University of Michigan’s Institute for Social Research] notes, “God’s timing couldn’t have been more perfect. If He’d come earlier in human history, how reliable would the records of his relationship with man be? But He showed up just before the exponential explosion in the world’s population, so even though 98 percent of humanity’s timeline had passed, only 2 percent of humanity had previously been born, so 98 percent of us have walked the earth since the Redemption.”
D’Souza goes on to discuss some other issues connected with this concept, such as possible reasons behind the apparent explosion of civilization approximately 6,000 years ago. Good stuff. Speculative, but still good.