Although I have some specific questions, there aren’t definitive answers for them probably, so I’m putting this in MPSIMS.
I’m watching “The Origins of Life,” on Hulu. The photography is stunning. And already, 15 or 20 minutes into it, I am stricken by the fact that we know a whole lot of the “whats,” but (necessarily, I guess) hardly any of the “hows.” The narration says things like, at this point, single-celled organisms began to join together for mutual benefit. Or, x years ago, organisms started reproducing sexually. But I have all these questions.
The example they showed of symbiosis-which-led-to-a-single-organism was coral. As I understand it, they were suggesting that a similar process may have led to the formation of new organisms, for instance, I have heard it speculated that mitochondria are likely to have originally been bacteria that entered into symbiosis with other cells. I know it can’t be proven, but are we pretty sure that that’s what happened? Are there other examples where we know for sure that one organism incorporated another, different organism, and produced a new creature altogether?
And about sexual reproduction – it’s hard to picture the steps leading up to this development, but it couldn’t have happened all at once, could it? Did the immediate predecessors to the first sexual reproducers just divide themselves, and the next generation do something new? What kinds of things could have precipitated such a development; I mean, how did organisms prepare to begin reproducing differently?
I have a good friend who insists that all evolution is the direct result of natural selection, pointing to the Peppered moth as an example. But I wonder if it is possible that a given population might sometimes respond to changes in their environment with an innovation that is not merely the result of a random mutation being better equipped for survival. Is it currently believed that sexual reproduction was introduced as a mutation?
(I don’t mean to tick off any actual scientists with foolish questions or ideas. This is just one of those situations where I find that my curiosity far outstrips my education.)