Blood as Costly Signaling in Evolution and Theology


Eugene Rogers is a member of the Human Distinctiveness Project, writing a book about how Christians think about blood. He is Professor of Religious Studies and Women’s and Gender Studies at the University of North Carolina.

The evolutionary theory of costly signaling seeks to explain not only sexual selection but how social animals gain fitness by sacrificing themselves for their group: among humans, the costliest signaling takes place in blood.  Blood is meaning made with bodies on the line. For that reason, both the biblical notion of sacrifice—“without the shedding of blood there is no forgiveness of sin” (Heb. 9:22)—and suicide bombings continue.

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Even theologians and humanists know a simple version of costly signaling. To signal evolutionary fitness, peacocks grow unwieldy tails and antelopes heavy antlers at great cost in calories consumed and mobility lost. Their ornaments supposedly help them compete among one gender for the favors of another. Religion seems even harder for evolution to explain: religious individuals do not just compete to reproduce, but they sometimes sacrifice their reproductive fitness altogether, as in joining a monastery, taking a vow of celibacy, or martyring themselves. Instead of dying out, even martyr-religions seem to flourish. But a more sophisticated application of costly signaling tries to explain this. The monk or martyr foregoes having one’s own children but secures social cohesion. Jesus was a martyr without children; Paul advised celibacy; but between them they founded a successful and cohesive group, Christianity.

Good at sorting costs and benefits, evolution itself shows what Director of the Center for Theology, Science, and Human Flourishing, Professor Celia Deane-Drummond has called creaturely wisdom. Some animals even seem to deliberate on cost. Is this display worth it, or does the animal withdraw? Other animals mislead with signaling that appears more costly than it is.

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Humans do something more distinctive than count or counterfeit the cost.  They use gesture and ritual, image, symbol, and language to magnify blood’s power to signal while lowering its cost, ratcheting their cultural niche to more and more subtle and effective signaling. The eucharistic ritual is powerful—many Christians find it more powerful than biological blood, because it is the blood of God. But in evolutionary terms, it’s a whole lot cheaper. The eucharistic wine is no counterfeit: no one is misled by it, even if they disagree on what theory makes it God’s blood. It is something else, which marshals humans’ distinctive ability to imagine and live into alternate futures and virtual worlds. Multiple societies have constructed their own environmental niches in which blood matters in more ways than one. Because they construct their cultural environment, they can also reflect on it; they begin to identify wisdom and folly. Despite its ties to oppression and war, blood-signaling, in our cultural niche, also fosters goods of virtue, cooperation, and gratitude—and therefore persists.

Because Christians worship a Logos made flesh and blood, God’s own costlysignaling, they ritualize growth and gratitude in blood’s terms. With “My Lord and my God,” doubting Thomas was told to put his fingers in the wound to make belief red and sticky. Blood images sustain the sacraments, where Christians find sacrifice and wisdom, grace and gratitude in bread and wine. “Taste and see that the Lord is good” (Ps. 34:8), used to invite one to communion, makes the throatiest of costly signals, where God became a costly signaler in the blood of the executed Word Incarnate.

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As I have written elsewhere,[*] blood may be red because iron compounds make it so, but societies draft its material qualities, its color and stickiness, for multiple purposes of their own. We imagine individual, social, and animal bodies as securely bounded. Inside, blood carries life. Outside, it marks the body at risk. Society’s work to maintain bodily integrity thus takes place in blood. It is the body’s permeability that leaves us bloody-minded. The body becomes a membrane to pass when it breathes, eats, perspires, eliminates, ejaculates, conceives, or bleeds. Only bleeding evokes so swift and public a response: blood brings mother to child, bystander to victim, ambulance to patient, soldier to comrade, midwife to mother, defender to border.

My book in progress, The Persistence of Blood, asks how Christians think with blood. They use blood to mark a social body through atonement, sacrifice, communion, kinship, and more. Contemporary disputes from evolution to women’s leadership seem to some Christians to threaten, to others to revive the social body that the blood of Christ structures, cleanses, and unites. Disputants use blood-talk to mark both external bounds and internal connections.  Rivals may set their opponents out of bounds as “impugning the blood of Christ.” Or blood may provide a vital language within which to disagree. This book brings theology together with the arts and sciences to show why conservatives invoke the language of blood and liberals at first avoid and then, at length, reclaim it.

[*] A version of this paragraph first appeared, for a different purpose and audience, in Eugene F. Rogers, Jr., “The Genre of This Book” (Review of Gil Anidjar, Blood: A Critique of Christianity), in Syndicate: A New Forum for Theology 2 (2015): 152.