The Atlanteans were governed by a council, who were apparently quite stern and conservative -- no doubt hardened by years of war with the Wraith, which they had recently given up any hope of winning.The elder Elizabeth uses the term "Lantean," the same used by the Wraith in reference to the former residents of Atlantis ("The Defiant One").With the exception of Janus, the inventor of the time travel device, the Ancients were strongly opposed to messing with the causal implications of time travel. The Atlantean Council condemned Janus's experiments in time travel and censured him; he was ordered not to build the time ship, and after Weir's arrival they ordered the remains of the ship and all research material to be destroyed. Janus disobeyed (again), taking his research with him back to Earth.
It is apparent that the Ancients maintained colonies throughout the Pegasus Galaxy -- perhaps because they outgrew Atlantis's planet during the millions of years they were there, or because they are explorers at heart (as Dr. Weir observed). (The latter is more likely, as the team in our time have yet to discover any Ancient cities on the planet outside Atlantis.) We know that, in addition to seeding the Pegasus Galaxy with human life, some Ancients also lived among them ("Sanctuary"). Thus the human colonies throughout the galaxy know the Ancients as their ancestors.Some of these planets also likely did not possess Stargates, otherwise the refugees returning to Atlantis in transport ships could have simply gated into the city. Janus was apparently the first Ancient to perfect time travel technology, though others of his species had apparently been working in this field of research millions of years ago. SG-1 once found a world where an Ancient colony had developed a device that uses multiple Stargates to loop time -- but they could not perfect time travel technology before they were wiped out by a plague (SG-1: "Window of Opportunity"). Melia, the female leader on the Atlantean Council, is the same woman who recorded the holographic message discovered by the expedition in our timeline, in which she described the Wraith war and the Atlanteans's ultimate decision to submerge the city and evacuate through the Stargate to Earth ("Rising, Part 1"). Despite their rejection of Janus's plans, they remained concerned about the future of the city and hopeful that humans might one day return.
Janus confirms that humans are the second evolution of the Ancients's form of life, something that has been speculated since the Ancient Ayiana was found frozen in Antarctica nearly three years ago ("Frozen").The Ancients who last lived in Atlantis 10,000 years ago were not ascended. They were mortal humans who escaped the Wraith by travelling to Earth through the Stargate. They had at some point studied ascension in Atlantis, however ("Hide and Seek"), though it is not clear whether any Ancients had ascended by this time. Some who remained in the Pegasus Galaxy did ascend at some point ("Sanctuary"), either prior to or after the Atlantean's escape.There was a small potted tree at the bottom of the stairs in the gate room when the last of the Atlanteans left, but it is not there when the expedition arrived from Earth. Obviously the tree died in the intervening millenia; the only explanation for the pot's absense is that Weir took it upon herself, either before entering the stasis or during one of her revival periods, to get rid of it.The Ancients who went to Earth through the Stargate 10,000 years ago likely integrated themselves into ancient human society, and brought more than the story of the city of Atlantis: They likely procreated with humans on Earth, introducing their evolutionarily advanced genes into the human gene pool -- resulting in the rare gene possessed today by Sheppard, Jack O'Neill, and others.
Janus brought his research with him to Earth and planned to continue his time travel experiments, though he was not sure he would get very far with the Atlantean Council watching his every move. He apparently did: SG-1 discovered one of the same model of time ships on a planet in the Milky Way Galaxy. | 
