According to one alternate version, this is where the dove never returned to Noah's Ark and thus they never found land, instead choosing to raise an egg that'd never hatch. The dove is now stuck caring for an egg that'll never hatch in an endless purgatory. The man is one of humanity's last survivors and as a way of putting the dove's soul at ease and letting the rest of the world finally move on, he cracks the lifeless egg, setting the dove free, leaving him alone in a world where the only dry land is the now overturned ark.