from what did the ancestry originate? how did the early cells assemble, what is the driving force behind the continued evolution, is it an advancing event? how often should we expect to evolve? is it possible to de-evolve at some points such as happens with diamonds back to graphite:
How far back do you want to go?
The first cells were little more than the self-replicating ribonucleic acid, contained in a fatty acid lipid.
If two of these cells came into contact, then the one that contained the larger amount of RNA would absorb the fatty acids from the other cell's lipid. As the RNA grew, the shell needed to grow too, so the one with more RNA would've absorbed the lipid from the other one, increasing the size of its own shell. As it grows, parts of it break off, forming new cells, with a copy of the genetic material.
Already you've got a "cell" that can replicate itself, genetic material included, and a "cell" that needs smaller cells to absorb, to keep on growing.
It's pretty complicated, and a a lot factors into it, such as what chemicals certain lipids would allow into the shell, whether or not the chemicals, when forming RNA would double over and loop, things liek that that would effect how much the genetic material replicated.
If it's single-celled organisms becoming multi cellular organisms, well, there's two ways it can happen. There are some species of single celled organisms that do it, and single cellular to multi cellular evolution has been witnessed in a lab.
Here's the one that was most likely the first:
As a cell divides, it's possible for a small part of the new cell to remain attached to the old one. Obviously, this isn't
actually a single organism, because there's no communication between the two cells. But because these two cells are now bigger, they would be better adapted to survive, because they're much harder for other cells to "eat", so over time, they'd get more and more advanced at being attached together. They'll grow new cells that won't detach, like the original two, and that'll happen a lot, until you've got a lot of related cells, all with the same genetic code, all attached together. It'd only be a matter of time until communication between the individual cells developed.
And well, that's pretty much the beginning of our ancestry.
The "advancing force" is simply to survive and copy as much genetic material as possible.
It's not possible to de-evolve, either, that'd mean having to lose genetic material in the order you gained it, and considering mutations are random, the chances of that happening are astronomical. Although, our DNA houses most of the traits we've had throughout our entire ancestry, so occasionally you end up with things like atavism, where these genes regress back to an earlier stage in their evolutionary history. Such as dolphins with hind limbs, humans with fully functional tails, snakes with legs or birds with teeth. What you'll never see, though, is an atavism which an animal has never had in its evolutionary history. You'll never see a hippo with feathers, or a komodo dragon with mammary glands or hair follicles.
