Precambrian environment (Introduction)

by dhw, Wednesday, October 30, 2013, 18:58 (4019 days ago) @ David Turell

dhw: A rise of up to 10% would be substantial enough to make a difference. But I really don't trust measurements of this kind. You can't help thinking that in a thousand years' time ... or even 100 ... all the calculations will be different.-DAVID: Again they were using isotopes with known half-lifes. Fairly trustworthy if you beliieve scientists.-I like your "if".-dhw: They cannot say how much, but there was PROBABLY ample...If you don't read these articles carefully enough, you come up with conclusions like: "There was lots of oxygen...".-DAVID: Oxygen has been all over the place in concentration. at one point as high as 25% which resulted in huge forest fires, as shown by ash levels at the layer of that time in history.-One theory is that the Cambrian explosion occurred because of an increase in oxygen. I really can't see anything in the article that undermines that theory. But of course it needn't be so. We just feel there must have been a trigger. Presumably your suggestion is that your God suddenly stepped in...but to do what, exactly? Change the environment (back to oxygen), or shove a few extra programmes into the automatons? -dhw: I find this very interesting. "A way of life that tried to evolve into a multicellular life form...", "...microbes that experimented with a way to evolve into some form of multicellular existence..." Margulis's concept of evolution proceeding through cooperation continues to gain ground.-DAVID: With whom? This is just stream of consciousness writing, no substance in fact.-Cooperation between cells and cell communities. That is how innovations take place, whether preprogrammed or not! Cooperation has been observed on a huge scale. You as a doctor are more aware of the science than I am, but even I know that without cooperation between the different cell communities in my body, I would be dead. The question is not whether they cooperate, but why they cooperate. You say they are preprogrammed to do so, and of course once the pattern of behaviour is established (the organ works), each cell ... like each ant ... plays its assigned role(s), but that does not explain how already functioning cell communities came up with new ideas. THAT is the great mystery.-DAVID: We do know what we don't know: how evolution really works.-True. And so we exchange ideas, test them, and argue the hind legs off each other.