Human symmetry

One of my favourite subjects in undergrad chemistry was Symmetry. Chemistry has a whole maths and nomenclature focused on the the symmetry of molecules. In order to get into this subject you have to have Asperges syndrome. Which I don’t and therefore my surprise (to this day) at my enjoyment of the subject.

That last paragraph was an attempt to enforce my credentials on what I am about to posit. Which is to say the lady is protesting before she even starts.

Here goes; have you ever noticed that we humans are supposed to be symmetrical on the outside but inside we are far less symmetrical? For example various organs are placed to one side or the other; the heart is on the left side, the right lung has more lobes than the left, the stomach and spleen lie to the left, and the liver has a single right lobe

As an aside, there are rare people who are ‘flipped’ and have these organs on the opposite side. A surgeon’s nightmare.

My suspicion is that the benefits of social cohesion have enforced external symmetry – it is easier/quicker to recognise a symmetrical friend or family member, and throughout history this benefit must have been enforced through the usual evolutionary processes.

No such benefit applies to internal organs so they have been free-er to wander about the body looking for the most efficient arrangement, but somewhat constrained by the external symmetry requirements.