Morality, a by-product of natural selection?

At first sight, mor­al­ity and sci­ence are two dis­cip­lines so dis­tinct that it would be inap­pro­pri­ate to con­fuse their respect­ive roles. How­ever, recent dis­cov­er­ies in cog­nit­ive neur­os­cience show the two dis­cip­lines are more inter­linked than pre­vi­ously thought, with the pos­sible involve­ment of neur­os­cience in the field of mor­al philo­sophy. But can we reduce man to the shape­less, grey­ish organ between his ears? Is he the product of his brain’s activ­ity? For the fol­low­ers of sci­entif­ic ration­al­it­ies, there is no doubt that the psy­cho­lo­gic­al, social, or mor­al self is car­ried out through oper­a­tions enabled by brain cir­cuits¹. Accord­ing to this point of view, there is a nat­ur­al­ist­ic inter­pret­a­tion of mor­al­ity that I will try to explain here.

Very early on, philo­sophy aimed to give a defin­i­tion of mor­al­ity, con­sid­er­ing it as being at the centre of our actions, as if it were a ref­er­ence point for cor­rect con­duct. In oth­er words, mor­al­ity and hap­pi­ness are linked since, if the pur­pose of exist­ence is hap­pi­ness, the means to achieve it are defined by mor­al­ity. It is there­fore not sur­pris­ing to find that in all cul­tures, humans are deeply con­cerned with mor­al­ity, for example by cre­at­ing insti­tu­tions such as courts to ensure that social norms apply to all.

Research in cog­nit­ive neur­os­cience is begin­ning to reveal the iden­tity of the brain cir­cuits involved in these mor­al judge­ments. We are dis­cov­er­ing that sys­tems for learn­ing about reward, assess­ing risk, and under­stand­ing the men­tal state of oth­ers are at work. How­ever, if they seem fun­da­ment­al to gen­er­ate a mor­al judge­ment, their degree of par­ti­cip­a­tion var­ies accord­ing to indi­vidu­al dif­fer­ences in terms of empathy, bene­vol­ence, or great­er or less­er sens­it­iv­ity to injustice. In oth­er words, each indi­vidu­al has his or her own threshold of sens­it­iv­ity to mor­al­ity. At the extreme end of this spec­trum, dis­turb­ances in the social decision-mak­ing cir­cuit gen­er­ate immor­al beha­viour such as that of psychopaths.

All mem­bers of human soci­et­ies, how­ever diverse they may appear, show a deep con­cern for issues of mor­al­ity, justice and equity². Humans are dis­tin­guished from oth­er spe­cies by their propensity to pro­duce cul­tur­al organ­isa­tions to ensure that social norms are respec­ted, includ­ing insti­tu­tions designed to assess the accept­ab­il­ity of indi­vidu­al beha­viour and to assign appro­pri­ate pun­ish­ments to those who viol­ate par­tic­u­lar norms³. Regard­less of how mor­al­ity may be con­cep­tu­al­ised, and fol­low­ing Darwin’s work⁴, research­ers argue that mor­al judge­ment is a human char­ac­ter­ist­ic that facil­it­ates cooper­a­tion among large groups of unre­lated indi­vidu­als⁵. In short, humans bene­fit from a spe­cial rela­tion­ship with oth­ers because it is totally dis­in­ter­ested, inde­pend­ent of a fili­al rela­tion­ship such as that which gov­erns the care of kit­tens by a cat.

The emer­gence of this men­tal fac­ulty would have giv­en Sapi­ens an adapt­ive advant­age that we can meas­ure today by the invas­ive nature of our spe­cies. As the mus­ket­eers used to say⁶, our spe­cies is liv­ing proof that liv­ing in groups improves an individual’s chances of sur­viv­al. Thus, mor­al stand­ards provide safe­guards against safety or health haz­ards, and the rein­force­ment of mor­al beha­viour min­im­ises crim­in­al beha­viour and social con­flict. In this way, mor­al­ity makes human soci­ety a viable enterprise.

On an evol­u­tion­ary level, mor­al­ity appears to be an extreme form of cooper­a­tion that requires indi­vidu­als to sup­press their own interest or to assim­il­ate it with that of oth­ers. The study of prim­ate or child beha­viour shows the con­served nature of this trait. It indic­ates that cooper­a­tion first arises from a per­son­al mor­al­ity centred on the indi­vidu­al and those close to him. Then, as a kind of exten­sion of this per­son­al mor­al­ity, a uni­ver­sal mor­al­ity emerges. It is from this second stage that indi­vidu­als fol­low and apply the social norms of the group. Mor­al­ity thus emerged over the course of evol­u­tion, becom­ing more com­plex, from a set of skills and motiv­a­tions to cooper­ate with one’s rel­at­ives at first, and then with everyone.

While anim­als obvi­ously do not expli­citly reas­on about right and wrong, vice and vir­tue, or just and unjust, some exhib­it beha­viours that seem to incor­por­ate sketches of vir­tu­ous beha­viour. Many spe­cies cooper­ate, help their rel­at­ives and care for their off­spring, and some already show an aver­sion to inequal­ity. Sim­il­arly, while social­isa­tion influ­ences mor­al devel­op­ment and explains why mor­al rules may evolve over space and time, human infants enter the world already equipped with cog­ni­tion and motiv­a­tion that incline them to be mor­al and proso­cial⁸. These early pre­dis­pos­i­tions to proso­cial beha­viour and socio-mor­al eval­u­ation reflect pre-wired capa­cit­ies that were adapt­ive for our ancest­ors. This pen­chant for cooper­a­tion with unre­lated indi­vidu­als would explain how our spe­cies became mas­ters and pos­sessors of nature⁹.

In sum­mary, the mor­al con­science observed in humans appears to be a con­sequence of sev­er­al cog­nit­ive, exec­ut­ive and motiv­a­tion­al capa­cit­ies that are the attrib­utes nat­ur­al selec­tion has dir­ectly favoured¹⁰. Dec­ades of research across mul­tiple dis­cip­lines, includ­ing beha­vi­our­al eco­nom­ics, devel­op­ment­al psy­cho­logy and social neur­os­cience, indic­ate that mor­al reas­on­ing arises from com­plex social decision-mak­ing and involves both uncon­scious and delib­er­ate pro­cesses that rely on sev­er­al par­tially dis­tinct dimen­sions, includ­ing under­stand­ing of inten­tion, aver­sion to harm, reward and value cod­ing, exec­ut­ive func­tion­ing and rule learn­ing¹¹. To sum up, human mor­al decisions are gov­erned both by stat­ist­ic­al expect­a­tions (based on observed fre­quen­cies), Bayesian infer­ences about what oth­ers will do, and by norm­at­ive beliefs about what oth­ers should do.