All available sources point to the Argalian Empire being extant after more than a thousand years. The race itself is not nearly so old as such a claim, and sporadic evidence would have one believe; dynasties of primitive rulers quickly evolved to meet the demands of their people for change, and the Empire as an entity has persevered through many conflicts, uprisings, and political upheavals. Though other nation states and governments on the Argalian homeworld rose to power, none besides the Empire were able to stand the test of time.
The ban on interstellar trade, communication, and immigration has only recently been lifted. The Empire is slow, and cautious in their approach to exposing their constituents to the influences of the Solarians and Core Worlders. Humans are colloquially referred to as Terrans by Argalians. The xenophobic attitude of the Empire isn’t necessarily shared by her citizens, however, and although the details of life beyond the Empire’s borders have been a secret for decades, details are now coming to light very quickly.
The average Argalian is humanoid on a basic level, but differs fundamentally from each of the other species in the sector. For one, Argalians possess only one ‘sex’, and the distinction between gender identities is nonexistent. The simple reality of the matter seems to be that Argalians have a unique approach to solving the issue of finding suitable mates. Based on their notion of what an Argalian believes a potential partner is both equipped, and attracted to, they will change their physiology to match those preferences.