Actually, it is a fairly straightforward process to construct a phylogenetic tree and determine what traits the original population had, and traits of descendent populations. The process works so well that you do not even need to know which DNA sequences come from the parent population. Once you run the analysis, you know exactly which sequence came from the original, and the order in which the child populations emerged.
The techniques of evolutionary biology are used a lot, in many contexts.
There are no known, verified truths ontologically dependent on those aspects of evolutionary biology which are imaginary or fabricated.
So there should be millions of transitory fossils and species yet there are none. You have to have a lot of faith to believe in evolution.
How did life begin?
Since I am obviously not as educated as you, I will have to take the word of other genetic scientists, who say that the process you are talking about still depends on the original assumptions that were made when the process was first figured out.
However, there will come a day when we will know the truth.
Please show one that has not been shown to be a fraud.