Humans alone practice religion because they're the only creatures to have evolved imagination.

That's the argument of anthropologist Maurice Bloch of the London School of Economics. Bloch challenges the popular notion that religion evolved and spread because it promoted social bonding, as has been argued by some anthropologists.

Instead, he argues that first, we had to evolve the necessary brain architecture to imagine things and beings that don't physically exist, and the possibility that people somehow live on after they've died.

Once we'd done that, we had access to a form of social interaction unavailable to any other creatures on the planet. Uniquely, humans could use what Bloch calls the "transcendental social" to unify with groups, such as nations and clans, or even with imaginary groups such as the dead. The transcendental social also allows humans to follow the idealised codes of conduct associated with religion.

"What the transcendental social requires is the ability to live very largely in the imagination," Bloch writes.