The Evolution of Morality: Origin and Validity

Summary

Evolutionary biology has produced substantial explanation of how human moral psychology developed. Sociobiology (Wilson), gene-culture coevolution (Henrich), and philosophical work on the debunking implications (Joyce, Street, Ruse) have together constituted a research program arguing that moral intuitions evolved for their effects on reproductive fitness rather than for tracking moral truth. The argument has been deployed against moral realism: if our moral beliefs are produced by selection pressures indifferent to moral truth, why should we trust them as guides to moral reality? Within Maslik 3 (Human), the framework engages this material carefully, distinguishing the legitimate evolutionary science from the debunking inference and applying the genetic-fallacy critique developed for the parallel debate about religion.

The Evolutionary Account

The evolutionary account of moral psychology has several components.

Kin selection. W. D. Hamilton's inclusive-fitness theory (1964) showed how altruistic behavior toward genetic relatives can be selected for. Moral intuitions favoring family members and kin would be reinforced by kin selection.

Reciprocal altruism. Robert Trivers's reciprocal-altruism theory (1971) showed how cooperative behavior between unrelated individuals can be selected when there is opportunity for future interaction. Moral intuitions about fairness, trust, and reciprocity fit this pattern.

Group selection. David Sloan Wilson and others have developed multilevel selection theory, in which selection operates on groups as well as individuals. Group-level moral norms (sharing, sacrifice, in-group loyalty) can be selected when groups with strong moral norms outcompete groups without them.

Costly signaling. Moral behavior serves as a costly signal of cooperative reliability, attracting better partners and improving social standing (Atran, Henrich).

Cultural evolution. The above mechanisms operate within cultural evolution as well as biological. Specific moral systems are cultural products that evolved partly through cultural-evolutionary selection.

The framework grants the descriptive value of these accounts. Human moral psychology has evolutionary origins; understanding those origins is a legitimate scientific project; the accounts have produced genuine empirical illumination.

The Debunking Argument

The debunking argument moves from the evolutionary account to a metaethical conclusion. Joshua Greene, Sharon Street, Michael Ruse, and others have developed versions of the following structure:

Our moral intuitions were produced by evolutionary processes selecting for reproductive fitness, not for tracking moral truth.
If these intuitions correspond to moral truth, it is by lucky coincidence, since the selection processes were not aiming at truth.
The probability of such lucky coincidence is low.
Therefore: our moral intuitions are not reliable guides to moral truth.

Sharon Street's "Darwinian Dilemma for Realist Theories of Value" (Philosophical Studies, 2006) is the most influential contemporary formulation. The argument is framed as a dilemma for moral realism: either the realist denies the evolutionary account of moral psychology (which is scientifically untenable) or accepts it and accepts that moral intuitions are unreliable (which undermines moral realism).

The argument has been engaged extensively in contemporary metaethics. It is not weak; it deserves careful response.

The Genetic Fallacy Application

The framework's response is parallel to its response to the analogous debunking of religious belief (see the-genetic-fallacy-in-religion-critique).

The bare genetic form of the argument — "your moral beliefs are produced by evolution, therefore they are false" — commits the genetic fallacy. How a belief is produced does not by itself settle whether it is true.

Street's more sophisticated formulation avoids the bare form: she does not claim that evolutionary origin proves falsity, only that it removes justification. The argument is structurally analogous to debunking arguments about religion: the question is whether the production process tracks the truth domain in question.

The framework's responses are also parallel.

Response 1: The tracking argument

Street's argument requires that evolutionary processes do not track moral truth. This is contestable. If moral realism is true and certain cooperation, fairness, and protection of dependents are genuine moral truths, then evolutionary processes that selected for cooperation, fairness, and protection of dependents would in fact have produced moral beliefs aligned with moral truth — by whatever causal route. The "lucky coincidence" framing understates the possibility that the evolutionary selection and the moral truth are not independent.

This response is most associated with David Enoch (in his work on moral epistemology) and parallels Plantinga's Evolutionary Argument Against Naturalism: if the cognitive faculties producing moral beliefs evolved in environments where moral truth and reproductive success were correlated, the faculties may track moral truth without having been designed to.

Response 2: The third-factor explanation

Several philosophers (David Brink, Erik Wielenberg, others) have argued for a "third-factor" explanation. Both moral truth and evolutionary selection are explained by some third feature (the structure of social cooperation, the conditions for human flourishing). The correlation is not coincidence but is grounded in the same underlying reality.

Response 3: The cumulative-case structure

The framework's broader strategy is cumulative-case. Even if Street's argument has some force against the reliability of any single moral intuition taken in isolation, the convergence of moral intuitions across cultures and across philosophical traditions — and the partial alignment of these intuitions with rational argumentation about moral truth — produces a stronger case than any single intuition would.

Response 4: The parity problem

Street's argument, like Plantinga's parallel argument against naturalism, has a parity feature. If evolutionary production of moral beliefs undermines those beliefs, the same logic applies to non-moral beliefs similarly produced. The faculties we use to reason about mathematics, physics, and even about the evolutionary account itself are evolved faculties. If evolution undermines our moral judgment, why does it not symmetrically undermine our judgment about evolution?

Street has engaged this objection (her response involves what she calls "constitutivism" about practical reason), but the response is contested.

What This Article Establishes

Contributions:

A presentation of the evolutionary account of moral psychology and its empirical achievements.
The debunking argument in its strongest contemporary form (Street's "Darwinian Dilemma").
The framework's responses, parallel to its responses to debunking of religious belief.
Recognition that this is one of the most actively debated questions in contemporary metaethics.

Limits:

The article does not claim that moral realism is proven. The framework's position is that moral realism is consistent with the evolutionary account given the right tracking conditions.
The article does not exhaust the metaethical debate. Specific moral theories (virtue ethics, deontology, consequentialism) are not adjudicated.

The Islamic-Tradition Resources

The Islamic tradition's resources on this question are worth noting briefly.

Muʿtazilī moral epistemology held that basic moral truths (the goodness of justice, the badness of cruelty) are knowable through reason independent of revelation. This position requires that human moral cognition track moral reality, and the Muʿtazila developed an account of pre-revelational moral knowledge ("al-ḥusn wa-l-qubḥ al-ʿaqliyyān") that would be congenial to a realist-tracking response to Street.

Ashʿarī moral epistemology held more strongly that moral knowledge depends on revelation, with reason being unreliable as a free-standing source of moral knowledge. The Ashʿarī position is more skeptical and would respond differently to Street's argument — perhaps granting it greater force, while preserving moral knowledge through revelation rather than through evolved intuition.

Māturīdī moral epistemology occupied an intermediate position: some moral knowledge is rational, but moral obligation specifically requires revelation.

The framework engages all three positions as resources for thinking about the evolutionary debunking question, without endorsing one against the others.

Connection to the Cumulative Case

Within Maslik 3, the evolution-of-morality question contributes to the broader case that pure material evolution is not explanatorily sufficient for the full human phenomenon. Specifically:

If the debunking argument succeeds, then evolved morality is unreliable, which is itself a problem for naturalistic ethics (and indirectly supports the framework's claim that the human is more than its evolutionary substrate).
If the debunking argument fails (via tracking or third-factor responses), then evolved morality can align with moral truth, but the existence of that moral truth is itself something the naturalist must accommodate — moral realism is itself a difficulty for strict naturalism.

Either way, the evolution-of-morality debate produces difficulties for the naturalist that contribute to the cumulative case of Maslik 3.

Connections to Other Masalik

Maslik 3 (this maslik): companion to the published objective-morality-realism-anti-realism-and- evolutionary-debunking, the-explanatory-sufficiency- question-what-defines-maslik-3, evolution-and-explanatory-sufficiency, and this batch's consciousness-and-physicalism.
Maslik 4 (Innate Religious): the genetic-fallacy response is developed in the-genetic-fallacy-in-religion-critique.
Maslik 1 (Philosophical & Metaphysical): the parallel to Plantinga's EAAN. See the-genetic-fallacy-in-religion-critique.

Key Distinctions

Evolutionary account of moral psychology (legitimate science) vs. evolutionary debunking of moral realism (philosophical argument requiring additional premises)
Bare genetic argument (commits genetic fallacy) vs. Street's debunking dilemma (more sophisticated; requires response)
Tracking response (evolution may track moral truth if it selected for cooperation in conditions where cooperation is genuinely good)
Third-factor explanation (both moral truth and evolutionary selection grounded in the same underlying reality)
Parity problem (debunking applies symmetrically to all evolved cognition)
Muʿtazilī rational morality vs. Ashʿarī revelation-dependent morality vs. Māturīdī intermediate position

Major Proponents (of the evolutionary debunking)

Michael Ruse — Taking Darwin Seriously (1986)
Sharon Street — "A Darwinian Dilemma for Realist Theories of Value" (2006)
Richard Joyce — The Evolution of Morality (2006)
Joshua Greene — Moral Tribes (2013)
E. O. Wilson — On Human Nature (1978)

Major Critics (of the debunking inference)

David Enoch — Taking Morality Seriously (2011)
David Brink — "The Autonomy of Ethics"
Erik Wielenberg — Robust Ethics (2014)
Russ Shafer-Landau — Moral Realism: A Defence (2003)
Alvin Plantinga — parallel EAAN argument
Knut Skarsaune — work on third-factor explanations