Facts supported by fiction in the game.
Vasudans are not ancients. There was attempts and subtle hints made at a connection between the two races, likely leading to the prophesy that spurred the HoL to go on its rampage and to give both species a hint about the coming destruction.
Ancients were as technologically evolved as the Terrans and Vasudans were when they were attacked by the Shivans with one critical difference. They were masters of subspace technology, by fluke, circumstance, or otherwise. This comes from the horses mouth...when asked about the Ancients, several people at Volition reported to us that Ancients were not any better than the GTA or the PVE.
The first attack that we know about from the Shivans was in Ross128 at GTI Rivera. The installation was destroyed by the Shivans and several scout wings engaged both Vasudan and Terran forces destroying them completely except for the ill fated pilot who made it back to Rivera.
Shivans took several weeks or months to find Vasuda Prime before they finally surrounded and destroyed the planet. There is little likely to support a previous attack 8000 years ago. The planet was always arid and inhospitable. The Vasudans evolved spaceflight probably out of a need to support their lack of resources. Its unlikely that the Shivans just zeroed in on it. Follow the rough order of events in FS2...Ross 128, Antares, Ikeya, Ribos, Vega, Deneb, Vasuda Prime, and so on. Thats definately not homing straight in but systematically wreaking havoc on many fronts at the same time.
According to everything we know from the Ancients narratives, their race was completely destroyed (although thats not something we can trust completely - we can assume that the story writers intentions were that the race was gone, finished, done for). There is absolutely nothing to suggest that the Ancients were Vasudans...a linkage is there in mythology, but it seems like the Vasudans were perhaps treated like children and ignored by the Shivans during their rampage the 8000 years before - no subspace, no threat.
The linkage between the first ever ship attacked in a mission bears no consequence. The first ever installation attacked was Terran...the first ever fighter to be attacked goes to a tie (the pilot reporting that "they slaughtered everyone" and refered to the Vasudans being destroyed too). The equal destruction is well noted in the storyline...neither side was spared any courtesy in any way regardless of what the mission tells us. The Aten destroyed by the first Shivan attack was more likely a story effort to show the player that Vasudans were also under attack, leaving no doubt that the Shivans were only after Terrans.