How long does it take to evolve?

Hi, Lamden.Welcome to EvC!I want to point out that I have a lot of skepticism toward any attempts to assign hard numbers to these things. In my opinion, not only is it a difficult answer to get, but it's also a rather meaningless answer to get.Evolution isn't an entirely linear process. At any given time, there are many lineages living, reproducing and mutating simultaneously, and there are many ways in which those separate lineages can intermix their genetic material. So, you effectively have multiple "generations" happening at the same time. So, we'll need a parameter to describe how many lineages are likely to have been going at once throughout Earth's history. We'll also need a parameter to describe what proportion of the accumulated mutation load of a given lineage is likely to be transferred into another lineage. Then, we'll also need some parameter to describe how many of those lineages will go extinct, irrevocably removing their accumulated mutation loads from the equation.To me, the game of parameterizing a model like this feels like sitting in front of a huge panel covered in dials, and arbitrarily dialing up and down until the numbers look reasonable to me. It's probable that any number I might fancy could be achieved by a variety of different combinations of the dials.So, even if this thread resulted in some number that we could take home, it would not satisfy me in the least. As much as I would love to have you convinced of the reality of evolution, I see no point in encouraging you to accept it because of some silly numbers game that we could only fail if we grew bored of constantly turning dials.

Hi, Lamden. Actually, the most primitive light receptor is thought to have been nothing more than a protein that was altered in some way when light struck it. This would result in a few subtle changes to the chemistry inside a primitive cell, which would in turn alter the cell's behavior and introduce selection for various means of exploiting this newfound ability to react to an environmental stimulus.Eyes have come a long way since then, of course. Those primitive proteins that reacted to light could later become the basis of photosynthesis (in which the light energy could be stored in chemical form) and the basis of vision (in which the light would be used to regulate the cell's behavioral rhythms to match the environment).I'd love to walk through the entire (theoretical) process of eye evolution, since it's a topic we've all discussed regularly and really has some cool bits to it; but let's go ahead and take it slow, because there's a lot to cover, and it isn't always obvious from a layman's perspective.Do you understand this "first step" in eye evolution?