If you listen carefully, History Channel doesn't actually say that. (implied heavily, and maybe it was different in earlier seasons, but I think "Ancient Aliens" ought to be required viewing for anglophone school children[1], because each episode starts from presenting factual information and slowly works its way towards very carefully hedged wild "conclusions"[2]. as with the sorites paradox the question to keep in mind while viewing is: when does the shark jump occur?)

[1] compare interpretation of reported speech in https://news.ycombinator.com/item?id=23614277

[2] "Ancient alien theorists conclude X. What if it were true?"