Yes, I am saying that scientists make the assumption that DNA can be used to map every living thing into a hierarchy.
That's not an assumption. That's a fact. A demonstrable, testable, verifiable fact.
Assuming you acquire the know how on how to do it, YOU could sequence genomes and map the matches.
And it will result in the same nested hierarchy. It will even result in the same nested hierarchy if you map matches from the context of comparative anatomy instead of comparative genetics.
This tree will even match the geographic distribution of species in context of plate tectonics and geological history.
As has been explained to you many times,
multiple independent lines of evidence, even coming from
accross multiple independent scientific fields, ALL converge on this exact same answer.
This is not an opinion. It is a testable fact.
We factually share more ERV's, or other genetic markers, with chimps then we do with cats.
Just like you factually share more genetic markers with your close cousin then with your distant cousin.
This is exactly how relationships between individuals are inferred. Like when you do a paternity test.
Or to see if some person is your actual sibling or cousin.
The fruit flies, and bacteria experiments were used to demonstrate evolution. If they were not considered a population, then evolution did not occur. Correct?
You're going to have to be a bit less vague then that.
I'm pretty sure right out the gates that no sinlge one experiment is going to have as goal "demonstrate evolution". Typically a single experiment will be testing a single
aspect of this HUGE theory.
So I suggest you do some reading and then, preferably in your own words, come back and state which exact experiment you speak off, what the purpose of the researches was and what results and conclusions were reached.
I probably am not getting you fully, on your understanding of population.
I have to go, but I will try to understand you on this later.
A population is a group of interbreeding individuals of a species.
If a population splits in two genetically isolated groups, we now have 2 groups of interbreeding individuals of a single species. This could happen if for example some natural disaster strikes, like a volcano or something or the creation of a river, splitting a population in two. Or part of a population migrates to other area's.
Due to this genetic isolation, genes aren't exchanged between the populations anymore.
Meaning that any mutations happening in population A, will stay in population A. They won't be introduced in population B, because there is no interbreeding going on between members of A with members of B.
If A and B end up dealing with different selection pressures, then A and B will gradually diverge from one another. To the point that members of A and B will no longer
be able to interbreed. Now we have 2 new species. Both are sub-species of the ancestral population species.
If the ancestral species was X, then both A and B are "types" of X. Subspecies thereof.
This is why humans and chimps are both primates. We share a primate ancestor.
This is why humans and chimps and cats are all mammals. We share mammal ancestor.
This is why humans and chimps and cats and crockodiles are all vertebrates. We share a vertebrate ancestor.
See?
This is what the nested hierarchy is.
This is the explanatory power of evolution.
This is how we were able to derive from this model that there must have been a vertebrate with both fish and land animal features, living some 350 million years ago in shallow waters, swamps. Researchers pinpointed rock of that age which would have found themselves in such an environment and started digging. And lo an behold, they found exactly what they were looking for. Tiktaalik. A land walking fish. Or a fish that can walk on land. Whatever your preference is.
Can you even fathom the body of knowledge and explanatory power that was required to make this prediction?