Philip Cunningham writes to say (and quote),
Michael Levin, a Distinguished Professor in the Biology department at Tufts, after giving several examples of top-down ‘biological form’, not bottom-up ’emergence’, being the ruling factor in embryological development, states that…
“OK, so one very canonical example of this that we discovered a few years ago is this. So here’s a tadpole, the gut, the brain, the nostrils, and the eyes here. This tadpole needs to become a frog. In order for a tadpole face to become a frog face, things have to move. So the jaw has to move, the eyes have to move forward, everything has to move. And it used to be thought that this process was hardwired because if you are a standard tadpole and you want to be a standard frog, all you have to remember is which direction and by how much every piece of the face moves. We suspected that there was more intelligence to this process than that, and so we did an experiment. We created so-called “Picasso’ frogs. So these are tadpoles in which everything is messed up. The eyes are on the side of the head, the jaws are off to the side, the nostrils are too far back. I mean everything is in the wrong position. And we found that these animals still, largely, make pretty normal frogs. Because all of these pieces will move in novel paths, sometimes they go too far and have to double back, to give you a normal frog.
“So what the genetics give you is not some hardwired system that always moves in the same way. What it specifies is a really interesting error minimization machine that, however you start it off, obviously within some limits, will try to minimize the error and get to the correct final shape. If we had a robotic swarm, a collection of robots that was able to do this we would call this a prize winning example of collective intelligence, but we don’t have such technology yet.
“So we started trying to understand this process. How does all this work? And so to this standard feed-forward, kind of open, process of developmental biology that you would read about in class, where there are genes, they make proteins… there’s some physics and chemistry, and then there is this ’emergent’ outcome (i.e. of the ‘anatomy’). Add to these feedback loops, whereby this is actually a homeostatic system. If that anatomy is disrupted in some way, by injury, by mutations, by teratogens, by parasites, whatever, then these feedback loops will kick in and try to minimize error. The cells will do what they can to try to get back to the correct shape. It’s a thing about your thermostat. It is a basic homeostatic circuit. Now, on the one hand, this is pretty expected. Biologists know all about feedback loops and so on. On the other hand, there are two kinds of weird and unusual things here. The first is that every homeostatic process has to have a set point. So, if you are going to try to get back to where you need to be, you need to remember where the right position is. You have to store a set point. We are used to thinking about scalars, single numbers, as set points, temperature, PH, things like that, but in this case the set point is some sort of a large scale geometry, It is a coarse grain descriptor of some kind of anatomy. A complex data structure. And, in general, biologists don’t love to think about goal directed processes. The idea is that there is supposed to be emergence (of anatomy), and that kind of emergent complexity, but this idea that things are working towards a goal, as any navigational system fundamentally does, is not something that is very comfortable, certainly for molecular biology.
“So how would something like this work? How could we have a navigating system that can have goals in anatomical space?” — Michael Levin – Where is Anatomy Encoded in Living Systems? – 11:33 minute mark
Well, when science is not comfortable with the evidence, either something is wrong with the science or something is wrong with the evidence. One solution is to ignore — or deprecate — the evidence. There is another solution but it’s controversial just now…
Merry Christmas to all, especially those stranded by bad weather! This is for you: