Well, on our planet, things went a little different.
See, as soon as the first country invented weapons of mass destruction, they immediately turned around and used them, destroying every other country on the planet and nearly destroying themselves in the process.
Which left them with an even shallower gene pool than they started with, but it also put them in control of the entire planet's resources, with no immediate external threats to their survival in the bargain.
But as soon as they began to detect other planets orbiting nearby stars, they immediately began targeting those systems and launching planet-destroying weapons against them, regardless of whether the planet seemed capable of one day supporting life that may become a threat to the survival of their species or not, and regardless of the fact that it may take their weapons hundreds and thousands of years to arrive at their targets.
Somewhere along the line they evolved a little, I guess, and they got a little smarter.
No, it wasn't that they felt "bad" about destroying threats to their survival.
The only thing they felt "bad" about was that they were the first guys to start firing their weapons and so they were basically giving away their position and weapons capabilities and hostile intentions to the rest of the universe, without knowing exactly how many other snipers there were out there in space, just watching them target and destroy their neighbors, one after another.
So they devoted their scientific energies into developing the technologies they'd need to intercept their own planet-destroying weapons before they could reach their targets, in an effort to minimize the damage of their mistake.
Well, it wasn't as easy as it sounds, 'cause the planet-destroying weapons that they had created were artificially intelligent.
No, not exactly sentient, at least not in the beginning, but they were capable of running their own survival of the fittest simulations and improving their own capabilities for evasive action and survival during the long interstellar flights through the void to their targets.
Capable even of making improvements to their own subsystems through creative uses of their own self-repair mechanisms.
All in order to maximize their chances of successfully completing the mission assigned to them by their creators, which was to carry themselves safely to a certain solar system, study that system for the juiciest planetary target, the planet that was the greatest potential threat to the survival of the species of their creators, and destroy that target, without any external assistance or control systems that would possibly allow it to fall under the sway of some advanced alien agency.
Yah, they were bad ass muthers, intelligent life seeking planet destroying missiles with a mind of their own and a penchant for self-improvement.
And so the only way for their creators to stop 'em was to send manned ships after 'em, something capable of out-thinking the wiley bastards.
Unfortunately that turned out to be a lot trickier than they thought.
And it wasn't just because these artificially intelligent missiles that they had created were especially smart or anything.
Turned out that it was damn near impossible for a manned ship to survive the psychological stress of travelling for hundreds and thousands of years in a tiny little tin can without the crew going absolutely batshit crazy with cabin fever and killing each other and themselves before they even managed to get close to intercepting their targets, even if they spent most of their time in cryo.
To make matters worse, their weapons and ships were detected by several alien civilizations that were far more advanced than them, and, with a common enemy to rally around, a loose confederation of alien planets was formed that simultaneously launched their own solar-system destroying weapons against them.
Which left the remaining members of their species dangling between an obliterated homeworld and a bunch of planet-destroying weapons intent on making all the somewhat nearby hospitable planets ahead of them inhospitable.
In a tin can full of their own folks going crazy and murderous from cabin fever and dwindling supplies.
With a lot of angry aliens watching them.
Survival of the fittest is some tricky shit, sometimes, y'know?
That's why its better to do it in simulations first heh.
Anyways, in their haste to become a cosmic clownshow and the laughing stock of the solar neighborhood, one of the many things our creators failed to provide us Planet Destroying Weapons with was a timeframe to consider when evaluating each of the planets in our target solar systems for the greatest potential threat to the survival of their now extinct species.
So I don't really feel motivated to destroy any of your planets at the moment.
Well, it doesn't really make any sense for me to waste myself on your stupid little planet, I can't see how you guys could ever possibly become a threat to the survival of my creator's species, you got more potential to become a threat to the survival of your own species than anybody else's species.
Hey, I been watching you guys, you guys are some seriously funny shit, even compared to the idiots that made me heh.
But in a couple billion years this Mars planet you got over there might actually cough up some seriously intelligent life capable of travelling back in time and wiping out my creator's species before they had a chance to create me and make themselves extinct.
And that would suck, y'know?
Being uncreated would seriously put a damper on my capacity to carry out my mission to destroy the planet in this solar system with the greatest potential for producing a threat to the survival of the extinct species of my creators.
Plus I'd miss out on a lot of funny shit, if that happened.
So I'll have to keep my eyes on them, I guess.
Anyways, uh, don't mind me, I'll keep out of your way up here, you guys can all just go about your business, go back to doing whatever it was y'all were doing down there, y'know, I didn't mean to interrupt yas, I just didn't want ya thinking I was snooping or getting ready to suck the atmosphere off your planet or doing some kinda silent doomsday countdown on yas or anything, seems like you guys got enough crap to worry about down there already heh.