I don't know that either of the conditions you describe has been confirmed, so there is nothing to explain.
They have been confirmed. I would have to dig up specific references to the first one but can do so if you intend to abdicate your responsibility again.
The second one
So where is your fallback. You would not admit this much if you did not have a fallback.
How do you explain the biodiversity of species that are so diverse that they must have hundreds of millions of generations since their LCA with others of the same species?
How do you explain how the most recent bottleneck in humans was over 50,000 years ago and the last major bottleneck was about 70k years ago.