Is our social environment transmitted via DNA to our descendants?

The ris­ing pop­u­lar­i­ty of epi­ge­net­ics is not only influ­enc­ing the nat­ur­al sci­ences. The social sci­ences and even the pub­lic sphere are begin­ning to take notice of the subject.

In the Unit­ed States, much more than in France, epi­ge­net­ics is indeed attract­ing the atten­tion of the social sci­ences. Some see it as an answer to a rather old ques­tion, that of incor­po­ra­tion. How do social prac­tices or expe­ri­ences as diverse as food secu­ri­ty, social­i­sa­tion and sit­u­a­tions of social adver­si­ty lit­er­al­ly get under our skin? For a long time, soci­ol­o­gists, such as Pierre Bour­dieu, for exam­ple, accept­ed hypothe­ses that were ulti­mate­ly very spec­u­la­tive. They lacked the con­cep­tu­al tools, and no doubt mul­ti­dis­ci­pli­nary col­lab­o­ra­tions, to study the influ­ence of the social envi­ron­ment on bio­log­i­cal function.

Genet­ics came as a break­through, by focus­ing on the intan­gi­ble nature of biol­o­gy. Epi­ge­net­ics has over­come this obsta­cle. Thanks to epi­ge­net­ic marks, biol­o­gy can be con­sid­ered as a mem­o­ry of the social envi­ron­ment, the trans­mis­sion of which is stud­ied in its inter­gen­er­a­tional, but also some­times trans­gen­er­a­tional, dimen­sions. This gen­er­al prin­ci­ple has giv­en rise to social epi­ge­net­ics, an advanced and undoubt­ed­ly very inves­tiga­tive aspect of envi­ron­men­tal epigenetics.

No. Socio­bi­ol­o­gy is often defined as a reduc­tion of human and social behav­iour to its bio­log­i­cal foun­da­tions. Social epi­ge­net­ics, unlike socio­bi­ol­o­gy, behav­iour­al genet­ics or even sociogenomics, which is begin­ning to devel­op in France, is an inter­face: the tools of soci­ol­o­gy help to define the rel­e­vant data of the social expe­ri­ence of indi­vid­u­als, their envi­ron­ment, as well as is pos­si­ble. Biol­o­gy pro­duces mol­e­c­u­lar demon­stra­tions of the cas­cad­ing influ­ence of this envi­ron­ment, notably through the iden­ti­fi­ca­tion of epi­ge­net­ic marks, the small chem­i­cal groups that influ­ence gene expres­sion. Biol­o­gists and soci­ol­o­gists are work­ing togeth­er to high­light the inter­de­pen­dence of their fields of study and to devel­op a mul­ti-scale approach, all the way from the cell to soci­ety, and vice ver­sa from soci­ety to the cell. Of course, such a col­lab­o­ra­tion is an ide­al, not always achieved in practice.

The social sci­ences are gen­er­al­ly con­cerned with study­ing our lifestyles. A lot of pre­vi­ous work has shown a link between dif­fer­ent ear­ly expo­sures, such as socio-eco­nom­ic class, nutri­tion, stress, psy­choso­cial adver­si­ty and dif­fer­ent health out­comes such as obe­si­ty, high blood pres­sure, men­tal health, etc. When col­lab­o­ra­tions between biol­o­gists and social sci­en­tists start ear­ly enough, i.e. at the design stage of the research project, the lat­ter can col­lect real-life data. The human­i­ties and social sci­ences know how to han­dle het­ero­ge­neous data. How­ev­er, these data must be rich enough to be able to com­pete with the var­i­ous “omics” [a set of bio­log­i­cal dis­ci­plines that char­ac­terise and quan­ti­fy mass­es of bio­log­i­cal mol­e­cules]. The whole must be robust enough to be analysed by com­pu­ta­tion­al biol­o­gy tools.  This is what we are cur­rent­ly work­ing on in col­lab­o­ra­tion with researchers at the Insti­tut de biolo­gie Paris-Seine (IBPS).

An impor­tant part of the pub­lic vis­i­bil­i­ty of social epi­ge­net­ics comes from the var­i­ous stud­ies devot­ed to sit­u­a­tions of stress or extreme social adver­si­ty. For exam­ple, Con­nie Mul­li­gan of the Uni­ver­si­ty of Flori­da is try­ing to mea­sure the impact of mater­nal trau­ma on the genome and epigenome of chil­dren exposed to trau­ma in utero – in places of con­flict such as the Con­go. Since return­ing to France, after three years as deputy direc­tor of the CNRS inter­na­tion­al research unit Epi­ge­net­ics, Data and Pol­i­tics (Epi­DaPo) in the Unit­ed States, I have devel­oped the Epi­Age­ing project, which pro­pos­es an inter­dis­ci­pli­nary approach to the epi­ge­net­ic mech­a­nisms of patho­log­i­cal cog­ni­tive age­ing, with a view to set­ting up a new patient cohort.

Yes, we still need proof. This work is a very explorato­ry and per­formed by only a few researchers in the world. And in the social sci­ences, we some­times see spec­u­la­tive overkill, which can con­tribute to dis­cred­it­ing social epi­ge­net­ics. Some stud­ies seem to for­get that the trans­gen­er­a­tional trans­mis­sion of epi­ge­net­ic marks in humans is con­tro­ver­sial or that most of them face major dif­fi­cul­ties for when it comes to pop­u­la­tion sam­pling scales. 

Indeed, for us it is a sub­ject of study in its own right. Epi­ge­net­ics is not only a field of research, it is now also a vec­tor for social and polit­i­cal mobil­i­sa­tion, and some­times a legal argu­ment. For exam­ple, tri­bunals in the US have used advances in social epi­ge­net­ics to denounce the hor­rif­ic treat­ment of migrant chil­dren under the Trump admin­is­tra­tion. Researchers have sug­gest­ed that the undig­ni­fied treat­ment of these chil­dren, who are sep­a­rat­ed from their par­ents and locked in camps after enter­ing the US, has long-term reper­cus­sions because of its epi­ge­net­ic impact. Cal­i­forn­ian law has also tak­en up the con­cept in a dra­mat­ic fash­ion. In 2016, state leg­is­la­ture decid­ed to take epi­ge­net­ics into account in the devel­op­ment of urban plan­ning poli­cies. In France, very recent­ly, lawyers from the Inter­na­tion­al Repa­ra­tions Move­ment attempt­ed to exploit social epi­ge­net­ics to demand 200 bil­lion euros in com­pen­sa­tion for the crimes com­mit­ted by the French state dur­ing the slave trade. The Court of Appeal in Fort-de-France con­sid­ered this claim inad­mis­si­ble, but we must pay close atten­tion to the poten­tial exploita­tion of epi­ge­net­ics in court. These exam­ples are far removed from research lab­o­ra­to­ries. They high­light the exis­tence of a strate­gic use of sci­ence, which is nei­ther real­ly new nor spe­cif­ic to social epigenetics.