The Ancient Aliens Debunked documentary aims to debunk not just some but all of the claims made in the 2010 history channel series, Ancient Aliens which has only fueled the fire on this theory. The Ancient astronaut hypothesis as it is also commonly known says that at some time in the distant past intelligent beings have visited Earth and made contact with human beings. The evidence to support such a hypothesis is how the meetings with these beings shaped how the human race developed in the areas of culture, technology, building design and religion.
The theory has in fact been around for a very long time as it was first proposed in 1919 by Charles Fort whose work has subsequently been followed up ever since. The idea of Ancient astronauts surely stimulates the mind but it has never really gained any credible endorsements from academics and remains in the realm of science fiction for many. Its presence is still very strong on the internet though.