Thank you for such an honest answer, in a sea of confusion.
The idea is that until "speciation" happened, the two (or more) subspecies could interbreed.
Which brings up the question, why would the interbreeding of say, a sub-simian and a sub-human produce an advanced (today's) human?
Now, regarding "intermediate forms", we don't know that a change of "form" is required at the time of "speciation".
Conversely, then, a change of form is no proof of speciation.
You got mom and dad of one species, and junior and his sisters are another ~ but they look pretty much alike ~ maybe identical.
You lost me on that one.
P.S. Thank you for the challenging responses.
Whatever "advanced" might mean, we need tests, evidence, results, experimentation ~ time for someone to visit the zoo.