In my view of history, all hand to hand combat is the same in one way, the human body is general vunerable in the same areas on everyone, to defeat someone you try to strike those areas. Martial arts define certain set of technquies used to hit those areas. So in my opinion as soon as one person said I have a better way to hit this person then you, you see martial arts formed. So in that way everyone can claim that all martial arts have been going on since the dawn of man.
As for those who site acient Korean History, I give one word of warning, most of the original text of history was destroied over time so what you are siting is the generally accepted history. Historians are currently debating the real history and some views may change over the next two decades. The basic stuff that is taught in middle school/high school will be the same but detials that go in college course may. As one of my history professors in my Asian Civ. Class use to say, "History is written by the winners and who knows what really happened any more"
I personally believe that Tae Kwon was created by General Choi, did he create every technquie? No but I believe that he orginazed it to what it was started to use to train the military. According to an interview from 2000 in the Tae Kwon Do Times, the late general studied Karate while he was a student in Japan and he did say that had some influence on him but he added that he wanted to give Korea an martial art that they could claim on his own. He admitted in the artical to force other schools to take the name and the South Korean Government didn't orgianlly want Tae Kwon Do because the president at the time liked Tang Soo Do and wanted that as the name and some the Kwans went with that.
In my opinion what has happened in Tae Kwon Do with the ITF and WTF riff, Choi didn't want that to happen. My School's Grandmaster Woo Jin Jung has stated that he hopes that Tae Kwon Do will become unified. In my view the only way to do that is that we forget parts of the past (personal fueds and governmental influence) and start working on a unifyed future were compermise is reached. We can sit and argue history or we can get up and work on the future.