Notice how all the colors at the top (representing ancestors) get to contribute their genes to those of the couple pictured at the bottom, but the red male at the bottom is descended in a direct paternal line from the red male at the top, while the green female at the bottom is descended in a direct maternal line from the green female at the top. The Y chromosomes and mitochondria are not the only things that get passed down from generation to generation!
Conclusion: always fear a Christian who becomes a staunch atheist for a few years who later converts back to Christianity. Not for the power of his intellectual argument (that’s optional, and, to be honest, rarely seen), but for his oft-seen inability to understand even the basic facts of what he’s talking about. If there’s one obvious thing every true intellectually free man quickly grasps (or at least should), it’s atheism. Turning back from it is a dead giveaway something has gone wrong on such a man’s train of thought.