I doubt this is original but it is worth going through because strange right-leaning people keep shouting about biology at me. Oddly though, I was prompted to write not by an argument about nature v nurture but a different argument about invention v discovery in mathematics. I’m not an expert on blood groups (which is sort of the point) so apologies for any biological errors.  Note also this is a description of one specific relationship between a social construct and biology. Others may have things in common but that doesn’t mean they are the same or have the same relationship between a biological aspect and the associated things that a society may construct around it [i.e. neither the social constructs of gender nor ‘race’ is directly analogous to blood group]. Anyway, here we go.

You probably know your blood group. Once upon a time I regularly gave blood and felt a moral obligation to do so. I’m O negative, which is a handy default blood type for donation as it contains neither A, B or Rh factors and hence shouldn’t trigger an immune reaction in most people of other blood types.

But ABO and Rh are just two blood typing systems and even with those two systems, there are variations. Group A can be further subdivided into approx 20 subgroups of which A1 and A2 account for most type-A people. In terms of inheritance, there are also exceptions to the commonly understood rules – CisAB (https://en.wikipedia.org/wiki/Cis_AB ). More generally there are tens of other blood typing systems that categorise other factors that can exist in human blood and which can potentially complicate blood transfusion.

The ABO/Rh system is a very effective simplification of a set of much messier, more organic categories. Yes, it is determined by your biology (you don’t get to pick) but the significance of whether you are “A” or “AB negative” etc depends very much on the existence and practicalities of a blood donation system. That system also has practical constraints but it is effectively something societies choose to do and requires political and social support as well as the existence of hospitals and an infrastructure to support them.

I also said that I used to give blood. I’m not allowed to currently because I lived in the UK during the height of the BSE/Mad cow disease outbreak. Concerns about the transmission of a prion disease via blood transfusion have meant that many countries place restrictions on blood donations. That rationale makes some sense given the extent to which prions are not well understood. What makes less sense is the restrictions imposed on men who have sex with other men (phrased that way to match the eligibility questions). Rules on blood donation to prevent the spread of HIV prevent people who have engaged in ‘at risk’ sexual behaviours (e.g. http://www.donateblood.com.au/faq/sexual-activity ). Such rules prevent many gay men in long-term monogamous relationships donating blood. The rules arise out of medical and practical considerations but such rules also have a social impact and arise because of social aspects (from international travel to personal and sexual relationships).

You should note another trick I employed above: I said ‘type-A people’. Once we have categories that can be applied to aspects of ourselves it is easy to see them as categories of people. I’m O negative, well no, no *I* am not, not really – my blood is O negative for the purpose of blood donation, it really isn’t much of a thing about who I am beyond that. The notion of me being O negative only really makes sense in the context of donating blood or receiving a blood transfusion (or a few other related circumstance). Prior to the development of safe blood transfusion and large scale blood donation, your blood group is not something people would know or care about. Even that history is entwined with complex social factors including the development of modern healthcare infrastructure but also the development of modern warfare.

Blood groups have also generated their own pseudosciences and racist theories – a kind of inevitable consequence of any system that allows a categorisation of people entails a dark desire to identify that categorization with other aspects including personality or as a means of identifying some inherent purity. Suffice to say there is little evidence of blood group actually determining anything other than the most likely blood needed in a blood transfusion (and as we’ve seen even that is a simplification – although a very effective one).

In most developed countries blood donation is voluntary but even such a primarily altruistic system has social implications. It isn’t had to imagine a situation in which blood donation was more heavily required or in which there were more significant socio-economic implications to donating blood. In such a situation the layers of social significance to blood type would be greater both in a direct sense and in the sense in which any social division generates its own myths and stereotypes. A world in which blood transfusions had to be more common and was connected to economic status, would with a capitalist-style economy lead to more weird (and unpredictable without knowing more details) stratifications by blood group.

So what’s my point if it isn’t a point about gender or race? The point is very much NOT that other social construct work the same way as blood group might in a fictional society. However, a broader point remains true. Critics of the term ‘social construct’ treat it as if a person is saying ‘wholly arbitrary’ or ‘completely made up’ or ‘fictional’. Treating the term like that makes it an easy strawman to knock down. No society exists in a vacuum*, so the things that our societies construct** are things that have practical limits and which are influenced by the environment that is constructed in INCLUDING the existence of other constructs. But the physical, ‘real’ influences on how a social construct has evolved over time do not mean that the categories, stereotypes or social expectations that arise apply in a deterministic way to individuals – some elements might (e.g. O- blood is safe for me to receive), others less so (e.g. whether there is a greater moral imperative for ‘O- people’ to donate blood) and others not at all (e.g. pseudoscience blood-group personality types).

tl;dr Societies and social attitudes are shaped by ‘real’ things including biology, but that does not imply that biology (or physics or chemistry) somehow validates them, makes them somehow extra true, or makes departure from them (either as an individual or as a direction for society) some kind of revolt against reality or science.

*[OK maybe there is a society of space squid, plying the void between the stars but that is a separate issue.]

**[You’d think that was obvious from the term ‘constructs’. Anything we physically construct has physical limits and depends on physical rules but can still be a work of creativity in which arbitrary, non-determined choices are made.]