Presumably they were in posession of older maps left behind by a civilisation that predates our own.

It is quite similar to the story of the Piri Reis map. Charles Hapgood noted that this map, focussing mainly on the Western coast of the African and the Eastern coast of the South American continent and Northern Antarctica, contained data which was not known to 'us' yet at that time.

Piri Reis compiled this map in 1513 AD. Antarctica wasn't officially 'discovered' until 1818.
Furthermore, the map outlined quite accurately the Princess Martha Coast of Antarctica, an area which is covered with an ice-sheet over a mile thick for the last 6000 years. Estimates say the last time this area was free of ice would have been prior to 4000 BC. We now know how accurate the map is because a seismic survey of this specific area (Queen Maud Land) was done in 1949, giving us the opportunity of detecting the make-up of the landmass under the ice.

This means that the original map (which Piri Reis used to compile his own) either predates 4000BC, or the ones who mapped the region had technology similar to our own, e.g. the possibility of doing a seismic study.

What we do know is that, despite confirmed existance of this map, no known human being physically reached the Antarctic continent until 300 years after it was compiled.

Handwritten notes on the map by Piri Reis himself inform us that he did not do any of the original surveying and cartography, but that he compiled it using a large number of older existing maps. Some of which he claims date back to the 4th century BC.

Strange stuff...

This proves for me that we know very little of our own past. Whether or not our Earth was mapped out by ET's or by older lost civilisations, we may never know. What we do know though, is that we inherited certian knowledge. This is a fact and the map stories prove this.

Too bad the library in Alexandria was burned to the ground. Apparently a lot of ancient scriptures / knowledge was lost then.

Well, although it of course is nothing new, it does concern a quite specific topic so in that regard I'm not surprised this is something not many people are aware of.

To be honest, I'm quite happy with the idea that the BBC is taking note. This sort of information should be brought into the public's view more often.

However, we must not forget that 'we' (with that I mean historians and scientists alike) aren't too fond of rewriting history. Especially if we can't explain certain phenomena using conventional thinking.

The Piri map for some people proves the existance of Atlantis to name an example. This is of course blasphemy, as it is common knowledge that Atlantis is a myth.... right?

Weathering patterns (marks of heavy rainfall) on the Sphinx shows it to be in existence already in 7000 BC yet we continue to deny this possibilty, despite our knowledge on historic environmental data of the region. Guess we are just too much indoctrinated to really find out the truth around such anomalies.

Let's hope 'news' like this triggers more people not to take what they learn in school for granted and keep an open mind.