You answered your question already. There's no info on exactly how long an Ur-Quan's lifespan exists. For all we know, a typical lifespan for them might last 5,000 years. Their culture certainly is highly evolved, and in typical games/sci-fi, the more evolved races tend to have longer lifespans, and thus would make sense.
And the Ur-Quan can't possibly be so long-lived -- the Kohr-Ah line when they first talk to The Captain when he has the neo-Dnyarri is "We sense... something... something ancient... a sickly smell... a chilling wind. My ancestors scream from within their chambers in my mind but I cannot understand their words. This feeling... a memory? It sickens us, and for the first time in our lives, for the first time in generations... We fear."
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Does anyone else pity the ur-quan in the end?.
Thanks for that I had a feeling that someone had mentioned something that related to genetic memory but couldn't remember who it was.
If The Quans (black and green) have genetic memory of the Dynarri then it explains everything. They could remember being enslaved in the few moments in which they were free, even generations later which would sort of lead to their extreme response which allowed them to truly defeat the Dynarri.
It also if you think about it supports all the theories about why the Ur-Quans' philosophies (or Doctrines) came about. To someone with genetic memory they KNOW the fear the suffering and the agony of generations and generations of being enslaved and being forced to destroy all they had once cared about. How can you not feel pity for them. With our 'normal' memories we only have our own experiences to bother us, imagine if we had all the memories of our ancestors, all the wars the pain and the suffering of each and every of our predecessors, wouldn't that cause us to become insane?
The Kohr-Ah's doctrine to 'cleanse' the galaxy of anything not Kohr-Ah is a sign of an unreasoning mind. The Kohr-Ah are literally insane from the experience of being enslaved and as such fight blindly to try and prevent it happening gain, to prevent themselves from being controlled again. While most of the races that the Kohr-Ah wish to wipe out cannot control them the Kohr-Ah cannot afford to make any kind of emotional attachments which would cause them pain if they were controlled again. (okay ill try and explain that a bit better)
*explanation* Losing friends because you are forced to exterminate them has got to be extremely painful. In the Ur-Quans case they were part of the Mileu and explored the galaxy with their other ally races. This leads me to believe that there were emotional links between the Ur-Quans and the members of the other races. (I remember that the Ur-Quans felt guilty for exterminating the races of the Mileu I cant remember where it was said so if anyone wants to dig that up I'd appreciate it). The Ur-Quans being forced to exterminate their friends by the Dynarri would be one of the worst kinds of pain imaginable. If the Ur-Quans have genetic memory that pain is eternal for them.
The Kzer-Za on the other hand are not insane with the memory but still fear the same result and as such anyone who threatens them, who doesn't submit to their rule is slave shielded. Not only does this prevent the Kzer-Za from being controlled it also means they don't have to suffer the guilt of genocide again.
I know that I REALLY pity the Ur-Quans'. While their actions are less than pure they have suffered horribly and if they can be reasoned with (and it wouldn't be easy, especially with the Kohr-Ah) I imagine that they could quite easily go back to their old exploration ways.