The environment as it settles into place is the determining factor. In a die off the environment is taken out of the equation…at least for the remaining survivors. They are then able to fill all the spots and voids…but is this through a lengthy process mutation and natural selection primarily? Or is the primary driver cross transfer where life remaining had to be given help and variation for change shared all over, across all domains of life?
We can all see mutation and natural selection maintaining for the environment. The groups that found their niche settle in more and more. But filling each corner of the current environment takes time. There’s descent from the original groups. They had that variation within them all along…it just needed exploitation. That’s where epigenetics steps in. It too is passed down through progeny…along with any alterations the environment hands out (if not too dramatic) and also any advantages. This is still maintaining for environment. The genes already developed within the group is turned on or off…and after time every single corner of our base current environment is filled. What was once thought to be the main driver of…all of this, that Darwinian model tree has been reduced to just one mechanism. It’s the maintenance guy or janitor cleaning up the place. And that’s why it’s now a bush of life, the variation for change coming from all over BUT at some point in all species past.
The genomes of all life shows a sharing of variation throughout it’s history. Even now it is still actively sharing and making changes but a small trickle. They know genetically there had to be a ton of sharing going on…because it’s within all domains of life. And…there’s quite a bit of ils or incomplete lineage sorting within descent. At the base of the BUSH of life…there are more than one trunk branching off, with intricate foliage covering the entire thing. When they say all domains that’s what it means.
Nested hierarchies still exist but within each main group, starting off with a lot of change then dwindling off as it’s used or exploited by nature. It’s always been there…but by epigenetics is turned on or off. The transition from each of these main groups though…is not something anyone can prove. It can’t be observed not genetically or by fossils. It remains a belief and interpretation.
Did life get plopped down here as the Bible says in each group…with large scale swapping of variation which resided within each…only to be expressed as time went on to fit the environment? Life Be! Multiply according to kind…
Or do you believe there exists transition from each group in a systematic manner over deep time?
What do you believe happened?