The core difference between Science and Theology is how they deal with statements of "truth" without evidence.
Theology starts with "it's true because I said so"
Science starts with "it's true because I can demonstrate it"
That humans were complex in the past is a good hypothesis. It needs evidence before it can be accepted as fact, or even necessarily expect respect from others. The lack of recent skull changes would seem to be a good start.
If someone believes the hypothesis to be true, they will go explore and find evidence to back their claims. If there was a complex society in the English Channel, it's likely well preserved, just waiting to be found!
To believe this is to cut yourself off from an unfathomably rich collection of human knowledge, and it is sad to see someone committed to it.
God speaks to someone. That someone says "It's true because God told me so."
I have read religious works, I'm not cut off from them. It's impossible to be cut off from theology in the USA. However, they all start with "it is true because I (the author) say so".
I think at least some of the people in this thread would argue against that, seeing as how it is about the idea of advanced or at least extant cities in the distant past. That would be exactly one of the points being argued on.
Similarly to biological evolution, on any sufficiently long time scale the descendents aren't more advanced, simply better adapted to different conditions. Our ancestors' societies reflected wildly different contraints and path dependence, not primitiveness.
I understand what you mean, yet I refuse to call concepts like universal human rights, rule of law and the unacceptability of war crimes as simply different adaptations, as opposed to being strictly more advanced than the predecessor ideas.