Including a side note on the lifespan of Humans. Destiny is an overturning collection of alien species that, in my opinion, put the Elites and Grunts of Halo to shame. In this case, each species has different classes and ranks that vary so much more than color and shield strength. My question, an open-ended discussion-worthy concept, where did these species come from?
Origin of the Enemy
We've already seen that Bungie is more hesitant to venture outside of our solar system in Destiny.
In Halo, there were thousands of inhabited planets that humans reached using, naturally, a made-up science-ish sounding method of transport called slipspace. My guess is Bungie, when first planning Destiny, realized that slipspace was just another warp speed or hyperspace. Additionally, it's scientifically unlikely humanity will ever venture beyond the solar system physically - it's more than 143 billion kilometers from the sun to the outer edge of the Oort cloud. So naturally, if Destiny wanted to remain realistic, it's unlikely the Cabal came from Deneb or Altair or Sirius.
So where did they come from, given we don't venture beyond our system's walls? Well, it's a different story for each species, naturally, so we'll find out.
The Vex seem to be the easiest species to point fingers on their origins. Bungie describes them as a time-traveling bio-mechanical race of mysterious intentions. If we remove the limits of time, the Vex could be from almost anywhere - from a Terminator-like future Earth to a planet that exists long after our Sun is extinguished.
The Cabal are a little trickier. They appear to be a strict military species situated on Mars. It's possible they existed from an earlier time when Mars was habitable, and were in cryostasis for many years under the surface. Mining operations during the Golden Age could have been a major cause of their domination.
The Hive and Fallen species are even harder to pinpoint. The Hive are somewhat easy, due to the Bungie "Moon" trailer implying that they lived deep beneath its surface until, as was suggested with the Cabal, mining operations unleashed them, possibly contributing the the Collapse of legend. The Fallen could have been from anywhere, though it seems like they lay dormant for a long time until humanity was at its weakest.
All of these are plausible ideas, but there is one that could explain the existance of all of the evil species. They could have come with the Collapse - from ancient and distant star systems, swept here in the wake of a huge and destructive blow on Humanity caused by the Darkness. They may have found a way to make it from their star systems to ours (each unique methods, likely), and saw our abandoned planets as a chance to create new homes. Of course this implies the aliens were indeed from distant systems, contradicting my earlier statement, but I contradict my contradiction by stating they may have lay dormant in ships for a while - drifting endlessly between star systems, like the Cassini, until they were awoken by the effects of the Darkness.
Keep in mind that the aliens came individually, and weren't part of any sort of team, because the Vex are at war with the Cabal, and the Hive are at war with the Fallen. We're not on two sides here.
But, in a Guardian's sense of things, who cares what side they're on or how they interact, really? This is our solar system, and they took our beautiful planets away from us. It's our job to take them back!
Origin of the Ally
So we have multiple ideas how the bad guys got to our system. But what about the good guys?
Humanity, as we all know, originated on Earth, evolving slowly over millennia into the most intelligent species of our world. But where did the others come from - our sister species, the Awoken, or the mysterious Exos?
First, and foremost I'd like to state that I seriously doubt the Awoken came from far away. Just look at this guy on the right (I think he's the Crow, but there's been no confirmation) - five fingers, hair, eyes, a nose, just like a human, only bluer. How can we just sit and think he's from a distant star system? My guess is he's from very close. But where?
One guess is they're related the the Traveler somehow. Maybe some humans were transformed into an alternate organism by its power, but somehow on accident. Or it could be just the opposite - the Darkness mutated some humans.
I really have no idea about the Awoken, but I do think I know what the Exos are.
They began as androids, created by Humanity to perform simple tasks. Over time new technologies made them powerful enough to become self-aware, and their structure was considered alive. After all, humans are basically nothing more than animate compilations of oxygen and hydrocarbon elements. Over time, the Exos developed a sort of co-civilization, living alongside humans. But something happened. During the Collapse, the Exos lost their memories, their emotions, and forgot about their past entirely. Because humans relied highly on Exos to preserve their legacy, humanity lost much of its history too, which is why Warlocks and other scientists are forced to rediscover the Golden Age. Exos are now cold, empty shells with nothing to live for.
A Note on Human Lifespan
I find it interesting to note that Bungie mentioned humanity's lifespan tripled in the Golden Age. Because the average lifespan in the USA is about 78.64 years, that means the human lifespan average would be 235.92. If this remains true to the Age of Reclamation, would that mean some humans could have lived to see the Collapse? If the game is set in the 2700s (let's say 2730), that means people could have been born as early as 2494. What would they have seen and done? Could they know where the Fallen and Vex came from, or recorded the lives of Exos before the Collapse?
Just a thought. Please comment with your thoughts on the origin of Destiny species or on my side-note on human life expectancy in the distant future. Thank you.