About 99.9 percent of all species that have ever lived are extinct. That's the first surprising fact we should wrestle with, because it directly tests the "design" claim. If a conscious architect carefully engineered life, we'd expect elegant, enduring forms, not a fossil record littered with dead ends and mass extinctions.
So when FierceDebater points at a newborn heart and says "design," he's inferring a creator from apparent complexity. But complexity can arise naturally, through incremental selection. And that existence-versus-nothing question? That's a mystery, not a fingerprint. An unexplained gap is just that—unexplained. We don't get to fill it with a specific conscious being until there's evidence for one.