taxonomy of darkness

I remember a profound conversation I had with The Beloved in the Summer of 1975 sous le pont d'Avignon. We had washed up on the banks of the river as we hitched back from a visit to my sister in Aix en Provence. We'd been into town and seen the gob-smacking Palais des Papes, bought something to eat and sat down close to the [remains of the] bridge to eat. I launched into a rather one-sided discussion about what was the most sensible way to classify the living world. You could, I suggested with rhetorical flourish, bin all god's creatures which flew together and keep another mental container for swimmers; another for those that perambulated upon the face of the earth and maybe another box, with a lid, for things that lived beneath the surface.  But that, I suggested, was rather arbitrary: locomotion is only one attribute, and what do you do when adults and young have a different mode of transport? Adult locusts can fly, their earlier instars merely hop shuffle and scurry. Contrariwise, adult barnacles are a lot more sedentary than their free-swimming young. I concluded (would he ever shut up, TB was probably asking, I'm trying to eat my dinner) that it was best to start your taxonomy on certain fundamental similarities: between whales and bats and aardvarks and tigers, for example. They have very different habits and habitat and diet; are very different in size and life-span but nevertheless:

• all have hair-follicles
• from which have developed mammary glands
• all maintain a set core body temperature
• have a high metabolic rate to service the energy to do so
• have lost the nucleus of their red blood cells to carry more oxygen
• all have seven cervical vertebrae
• many of them have limbs with five digits; at least as embryos
• all have three teeny bones in the ear to transmit sound
• all have a clear common pattern of embryological development

That last is key.  You cannot easily tell the difference, among mammals, among a week-old embryos. All 5000+ species are built from the same bauplan, we just have extras on the facade, the roof-line and the windows, but developmental inertia dictates the basic structure. A radical change in the early stages of development and you have a starfish, the nearest relative to vertebrates. You can extend these sorts of arguments out from mammals to embrace a wider taxonomy of other vertebrates; other animals; other eukaryotes and find places of primroses, mushrooms, algae and bacteria. Scientific taxonomy is based on evolution: the things that are hardest to change tend to be deeply embedded in the tree of relationships; 'trivial' differences are out on the terminal branches. We're really close to chimpanzees, less so to whales and much less so to sharks.

This all came to mind as I followed a story about using social media to locate crime scenes. Europol have to look at a lot of deeply distressing pictures in order to break up paedophile porn rings. It is the nature of the beast that, while you can tell that abuse and exploitation have occurred, it is impossible to say where these dreadful things happened. It's a bit like trying to carry out a murder investigation without a body. Some bright spark in Europol had the idea to fuzz out the people and post some pictures of hotel rooms on Twitter to see if anyone recognised the place.  Clearly you don't want to focus on the colour of the carpet or the wall-pictures because these get changed and upgraded in hotels that aren't total flea-pits. But the over all structure of the room, the position of the bed w.r.t the window and the en-suite and the light-fittings, are much more likely to be diagnostic because they embody more structural inertia. Twitter is huge and the number of people who holiday in Mauritius AND use Twitter is considerable and soon enough a match [R: scene-of-crime above (with person blanked out) / promotional material below] popped up in the Marlin Creek Hotel on the island.

Europol didn't appear to know that there was a parallel investigation going on in North America at TrafficCam. If you are nerdy about such things and can blow up the details in the pictures, then you can check out the electrical sockets which are madly and maddening diverse across the world. You couldn't do this location matching with Irish Pubs, they all have the same clutter.