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.