Hi John
Until common ancestry is clearly defined we will be talking over each other. Without a clear definition the current post does not make any sense.
If common ancestry is simply represented as explaining the pattern of the changes (tree) this explains very little.
The fix here is maybe to start evolutionary theory assuming the existence of populations and don’t try to explain their origin as physics is not trying to explain the origin of matter.
Starting with populations takes away the problem of trying to explain the dramatic observed differences in the diversity of life.