Most current theories are gaining evidence that between 11,500 bc and 9000 bc was a period of heavy flooding and geothermal/tectonic activity. Rather it was melting caps, meteor strike, or divine flooding is still up in the air. In any case, about 12000 years ago the planet changed drastically. This much is supported pretty much universally.
Egypt/phoenicia (sp?) is no longer thought to be the oldest traces of civilization. Instead they are considering some sunken ruins off the coast of Japan, an elevated plateau in South America, and a few other remote locales. They've estimated these new places to date back to the period of flooding, between 12,500 and 9000 bc, but exact findings are still sketchy. This predates the previous earliest traces which dated to about 4500bc (such as the pyramids, and early phonecian settlements).
That a civilization of advanced technical knowledge existed before the 4500bc era is no longer seriously doubted by most historians. Some are willing to entertain that it was 'Atlantis', while others remain certain that it was the forefathers of known early civilizations -mayans, incas, toltecs, etc. The sudden existence of advanced architecture, art, medicine, and other societal tells at around the 6000-4000 bc period is fairly convincing evidence that it all came from someplace.
Furthermore there is an UNCANNY resemblence between egyptian, south american, pacific islander, and asian ultra-early leavings that suggest they ALL had a similar origin.
Some of the more telling evidence I've personally heard:
similarity of 'pyramid' constructs on 4 different continents...all suddenly appearing about the same time.
worldwide tradition of a 'great flood' which cast down previous civilization.
mediterranean literature and other records which discuss vast civilizations to the west, and in many cases even describe Atlantis, it's people, and it's accomplishments.
Orichalcum - DUDE! That stuff is INSANE.
growing geological data concerning MASSIVE changes around 12500-9000 bc.
computer modeling showing possible migration and spread of ideas/people done 'assuming' that a global flood did occur at about the time discussed. It's the first solid planetary evolvement connection I've ever seen.
Anyway, I'm not saying Atlantians were aliens or anything, nor that the bible is true, nor that anything in particular is exactly what happened. I am saying that after a LOT of research it seems obvious that more went on before 4500bc than has ever been talked about before, and it's time to give it more serious scientific study.