There was more harmony between themselves, their other-selves, and the earth.  Therefore life wasn't as hard to live back then, more harmony = longer lifespans.  Look at how short the Egyptians and the early colonists in America lived.  I think about the whole 6000 years old stuff just has to deal with the old testament existing.  I mean the great flood was about 11,000 years ago, lets see what Ra has to say about 2 great civilizations before the Old Testament was even thought of, the Lemurians, and the Atlanteans.

"Ra: I am Ra. This is the last question of this working. The civilizations of Atlantis and Lemuria were not one but two. Let us look first at the Mu entities.

They were beings of a somewhat primitive nature, but those who had very advanced spiritual distortions. The civilization was part of this cycle, experienced early within the cycle at a time of approximately 53,000 of your years ago. It was an helpful and harmless place which was washed beneath the ocean during a readjustment of your sphere’s tectonic plates through no action of their own. They sent out those who survived and reached many places in what you call Russia, North America, and South America. The Indians of whom you come to feel some sympathy in your social complex distortions are the descendants of these entities. Like the other incarnates of this cycle, they came from elsewhere. However, these particular entities were largely from a second-density planet which had some difficulty, due to the age of its sun, in achieving third-density life conditions. This planet was from the galaxy Deneb.

The Atlantean race was a very conglomerate social complex which began to form approximately 31,000 years in the past of your space/time continuum illusion. It was a slow growing and very agrarian one until approximately 15,000 of your years ago. It reached quickly a high technological understanding which caused it to be able to use intelligent infinity in an informative manner. We may add that they used intelligent energy as well, manipulating greatly the natural influxes of the indigo or pineal ray from divine or infinite energy. Thus, they were able to create life forms. This they began to do instead of healing and perfecting their own mind/body/spirit complexes, turning their distortions towards what you may call negative.

Approximately 11,000 of your years ago, the first of the, what you call, wars, caused approximately forty percent of this population to leave the density by means of disintegration of the body. The second and most devastating of the conflicts occurred approximately 10,821 years in the past according to your illusion. This created an earth-changing configuration and the large part of Atlantis was no more, having been inundated. Three of the positively-oriented of the Atlantean groups left this geographical locus before that devastation, placing themselves in the mountain areas of what you call Tibet, what you call Peru, and what you call Turkey."

So there you see that the Old Testament is just a history book, nothing really spiritual about it.