When Darwin handed over the baton to Churchland

Inspired by Patricia Churchland’s talk “The Neurobiology of Moral Conscience” at the Forum Scientiarum (6 June 2018), I discuss the evolutionary basis of morality and how our moral norms started to build on the intrinsic nature of pro-sociality. Let’s take a closer look at this.

From a materialistic philosophical perspective, everything is a consequence of material interactions. The same holds true for our minds. Our minds and consciousness are thought to emerge from material interactions coming from chemicals within our nervous system1. Materialism is also supported by the Theory of Evolution and explains the ramifications of human conscience, including morality.

Morality helps us discriminate between proper and improper intentions, decisions and actions2. The aforementioned distinction is often part of sociomoral dilemmas. People are frequently confronted with the dilemma of acting in a purely self-serving manner or displaying cooperative, prosocial behavior. This conflict gave rise to one of the most vexing philosophical questions: Are we intrinsically selfish or pro-social entities?

The intrinsic nature of sociability

Aristotle (384 – 322 BC) stated that: Man is by nature a social animal; an individual who is unsocial naturally and not accidentally is either beneath our notice or above human” 3.

Charles Darwin (1809 –1882), a pioneer in the Theory of Evolution (Figure 1), grasped the baton from Aristotle and compared human and animal behavior. He concluded that the origin of moral sense is based on species’ sociability, as reflected by cooperative actions observed during group activities, such as fighting, hunting and food sharing. Instinctive sympathy started developing within the course of evolution and natural selection, as means to minimize inter-group conflict. Accordingly, uncooperative agents are more likely to exhibit low fitness (i.e., measure of reproductive success), as group members tend to punish selfish behavior4. According to Darwin, any animal endowed with well-marked social instincts would inevitably acquire a moral sense. He, further, emphasized that the difference in morality between humans and animals is “certainly one of degree and not of kind”5. Albeit, most animals can exhibit pro-social senses, non-human animals cannot reflect or recognize the underlying intention in a decision or action. That brings us to the next question: What makes a human being morally distinctive? Conscience emerged as the main difference.

Figure 1: Charles Darwin, pioneer in the theory of evolution.

The descent of a “Moral” Man

The origin of the modern concept of consciousness is attributed to the appearance of homeotherms (i.e., animals with constant body temperature) and the associated need for greater energy to maintain body temperature at high levels6,7. In accordance, more energy intake facilitated the expansion of the nervous system and the development of an organized, layered cortex8.

Albeit, all mammals share the basic layout of the cerebral cortex (Figure 2), the prefrontal cortex (PFC) in our brains occupies a larger percentage than in any other animal. Our ability to act in an “appropriate manner” is deemed to be dependent on the well-functioning of the PFC.  That is also the reason why damage in this frontal area has been associated with lack of self-control and impaired social and moral behavior9. Besides the enlarged frontal lobe, human cortex has higher neural packing density; a determining factor of general information processing capacity as reflected by general intelligence10.

Everything comes with a price.

From a developmental perspective, a human child’s brain undergoes an impressive increase of synapse density between conception and age three and continues, with a diminishing rate, into early adulthood11.  Such long maturation processes increased the need for parental care, eventually resulting in a substantial cognitive payoff.

Handing over the baton to Patricia Churchland

Patricia Churchland, a neurophilosopher working at the interface of philosophy, neuroscience & psychology, picked up the baton from Darwin and examined the neurochemical underpinnings of pro-social behavior. Churchland argues that moral sense is rooted in early life mother-infant attachment. The corresponding neural platform involves the hypothalamus (Figure 2: located under the thalamus), with oxytocin and cannabinoids receptors solidifying the bond between caregiver and infant12,13.

Figure 2: Neuroanatomical underpinnings of moral behavior in the prefrontal cortex and hypothalamus.

Similar receptors are also found in the brain’s reward system, highlighting the pleasure derived from social cooperation. Social phenomena, such as fanaticism may presumably “leverage” this evolutionary preserved circuitry; fanatics often exhibit an overwhelming sense of identity based on a community, while sharing tight bonds among their conspecifics. A “special pleasure of mutual sympathy” seems to go hand in hand with group belongingness15.  


But what about rules?

The evolution of moral norms

Conversely, moral norms (i.e., rules of morality that people ought to follow) entail a learning component. The interplay between subcortical and cortical areas support the necessary learning processes (i.e., classical and operant conditioning) for the constellation of norms. Here, culture and society begin to make their presence felt, shaping large moral systems. These rules and institutions, crucially, vary from place to place, and over time. This can be illustrated in cross-cultural studies assessing economic behavior. In the ultimatum game, for example, a “proposer” offers a portion of a total sum of money to a “responder”. The responder can either accept or reject the proposer’s offer. Strikingly, the offer “threshold” is not fixed across cultures. For instance, “Machiguenga proposers” provide less equal shares to responders (26%) as opposed to “Los Angeles proposers” (48%). The percentage of offers is deemed to be proportional to the degree of group bonding and demonstrates the influence of the environment upon our moral standards15. Hence, a genetic predisposition intertwined with ecology, is thought to navigate via basic learning mechanisms our moral compass.

The morality of everyday life

In our everyday life, social context can often result in rivalry (e.g., shall I cheat on a test or not?).

Are we consistent in our moral choices? Not really.

The ever-changing social and individual frames and their complex interaction prevent the unraveling of decision-making strategies. Albeit neuroscience has advanced remarkably, little inference can be made about the observed neural correlates of moral decisions. That is why the clarification of human decision mechanisms under moral uncertainty and conflict is one of the great “neural” challenges of morality research.


The dark side of the moon: selfishness

Oxytocin is evidenced to support prosocial behavior and to be inversely proportional to stress. Indeed, stress responses in humans can be attenuated by exogenous oxytocin administration, while stress-buffering is notably moderated by social factors16.


Can this inverse relationship be explained in moral terms?

Stress enables organisms to respond quickly in crucial situations that require immediate action (fight) or retrieval (flight)17. Importantly, a perceived threat promotes feelings of anxiety, which often triggers selfish impulses as a means to restore the “threatened-self”18. The physiological response to stress commences with the hypothalamus corticotropin releasing hormone, followed by a chain reaction and ultimately leading to the excretion of cortisol19.

We may conjecture that the neurochemical imprints of selfishness and sociality lie deep in the brain. The hypothalamus evolved to regulate survival instincts, along with which cooperative and selfish impulses emerged. Oxytocin could have evolved as the neurochemical mediator subtending cooperation under rest, whereas cortisol instigating self-centered behavior under threat. The moral foundations may have emerged from two survival mechanisms: one wearing a “pro-social” veil and another a “selfish one”.

Rea Antoniou is a Master Student of Neural & Behavioural Sciences at the GTC in Tübingen.

Photo sources:
Open source from Pixabay.


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[2] en.wikipedia.org/wiki/Morality

[3] Aristotle ([350 BC], 2000). Politics, Book 1, section 1253a. New York: Dover Publications.

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[5] Darwin, C. R. (1871). The descent of man, and selection in relation to sex. London: John Murray.

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[11] Stephens, K. (1999). Primed for learning: The young child’s mind. Child Care Information Exchange, 126, 44-48.

[12]  Churchland, P.S. “The Neurobiological Platform for Moral Values.” Behavior 151. (p.291)

[13] Lim, M. M, & Murphy, A. Z, Young LJ (2004) Ventral striatopallidal oxytocin and vasopressin V1a receptors in the monogamous prairie vole (Microtusochrogaster). J Comp Neurol 468:555–570

[14] Smith, A. (1982 [1759, 1790]), The theory of moral sentiments, in: D.D. Raphael and A.L. Macfie (eds.), Glasgow Edition of the Works and Correspondence of Adam Smith vol. I, Liberty Press

[15] Henrich, J. (2000). Does Culture Matter in Economic Behavior? Ultimatum Game. Bargaining among the Machiguenga of the Peruvian Amazon. American Economic review

[16] Olff, M., Frijling, J. L., Kubzansky, L. D., Bradley, B., Ellenbogen, M. A., Cardoso, C., et al. (2013). The role of oxytocin in social bonding, stress regulation and mental health: an update on the moderating effects of context and interindividual differences.   Psychoneuroendocrinology 38, 1883–1894.

[17] Cannon, W. B. (1913). The emergency function adrenal medulla in pain and the major emotions. American Journal of Physiology, 33, 356–372.

[18] Eysenck, M. W., Derakshan, N., Santos, R., & Calvo, M. G. (2007). Anxiety and cognitive performance: Attentional control theory. Emotion, 7(2), 336– 353.

[19] Ulrich-Lai, Y. M., & Herman, J. P. (2009). Neural regulation of endocrine and autonomic stress responses. Nature Reviews Neuroscience, 10(6), 397–409.


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