As of ME3 it was implied that the Reapers generally destroy civilizations at some point after they've attained the means to create a true artificial intelligence. That being said there was at least one Bronze Age civilization that was possibly destroyed by the Reapers. (We don't know for sure that it was the Reapers)
Assuming for a moment that the Bronze Age civilization was destroyed by the Reapers, than it isn't entirely clear what factors determine whether or not a pre-space flight civilization is spared for the next cycle.
The Reapers do spare some pre-space flight civilizations however. Their invasions don't necessarily wipe the galaxy clean of sapient life. Anatomically modern humans have been around for about 200,000 years. That would mean that not only were humans spared during the Prothean cycle, but they were spared during the Inusannon cycle as well. I'm not sure if a date is given for the cycle prior to the Inusannon, but given that the cycles average out to about 50,000 years apart it is possible that humanity survived a cycle prior to the Inusannon's extinction. The Inusannon went extinct 127,000 years prior to the events of ME1.
We also know that the Asari, Salarians, and Hanar were spared during the Prothean cycle because the Protheans were involved in studying all of them. In the case of the Hanar, it was implied that it was Prothean genetic engineering that gave them sapience.
Other than the Hanar we don't know how old any of the other space-fairing species are in the Mass Effect universe, but its probably safe to assume that most are at least as old as, or older, than modern ****** sapiens. Like humanity, they've might have survived multiple cycles.
Modifié par Han Shot First, 22 février 2014 - 06:56 .