How long does it take to evolve?

What was the most primitive form of life and when did it appear?What was the earliest "human being" and when did it appear?Lamden's question, with multiple undefined terms and assumptions, is the kind of question usually followed by a creationist "Gotcha!" to any honest attempt at a reply: any numerical answer is vulnerable to the critiques outlined in this thread; refusal to speculate can be met with charges of "then you have no case."If he has looked into the debate with creationists at all, and he suggests that he has, then he should be familiar with this adversarial context and honestly admit both the question's unanswerable nature and the good reasons for wariness.

I actually knew those answers, more or less, but I was curious about Lamden's take on the questions. An honest reply from Lamden would have been revealing, I think.But I apparently put myself beyond the pale earlier, and no longer merit his replies.I will soldier on.

Why would you want to join a club that would accept you as a member?

Mind your humility: 5.0 of that is for Calvin & Hobbes.

Your level of incredulity is high, Lamden, but only with regard to science. I assume there are religious tenets at work. I don't deal well with that kind of preemptive obduracy, so I'll post this as an exit from the thread.You balk at the notion of gradual stages of eye evolution, because you think there must be a brain for any of those stages to confer any benefit.But photoacceptors, molecules that react to light, exist in single celled organisms like E. coli; in fact, some wavelengths of light promote population growth and others inhibit it. In a local environment, this has the effect of shifting the (now larger) population toward the beneficial light source.In addition, E. coli can be motile. So only one change would be required to produce a bacterium that moves toward the good light: essentially, the detection of that light already exists (in the stimulated metabolic pathway) and the ability to move to that light already exists. Add a tropism, with the motile bacteria reacting to and thus moving 'upstream' a gradient of goodness (light), and you've got productive 'vision' with nary a brain.Every benefit of vision that you think requires a brain is exhibited in single cell organisms: photoacceptors, photosensitives, phototropics, photophilics...and keep in mind that bacteria can exchange packets of beneficial genes. What seems impossible to you for evolution to achieve in vertebrates was sketched out by single cell organisms long before vertebrates existed. What were the odds when you consider those billions of years and add an incalculable number of organisms working on the problem sharing steps in its solution?It took me 20 minutes on Google to trace the discovery that some broad wavelengths promote and some inhibit bacterial growth (19th century), that monochromatic lasers can refine the effect (1980s), that optimal levels of intensity, pulse frequency and wavelength can be determined for an effect (1990s), and that precise correspondences can be established between specific wavelengths and specific metabolic pathways in E. coli--an organism that cannot long survive outside the darkness of our guts. Light got in the picture early.Beware of how easy it is to believe what you'd like to believe. Look around. Life is infinitely more clever than theology.Edited by Omnivorous, : No reason given.