Ever try to pass someone only to have them speed up to block you out? Asshole! Well, have you ever been that asshole? Why do people drive like it's a race?
The explanation seems obvious on the face of it - it's rude to try to get ahead of someone. People don't like being passed.
We all know it's not a race. We all understand that we'll all get to our destinations faster if we cooperate. We all know that letting someone pass you doesn't slow you down at all. We all know Wal-Mart will probably still be there when you get there, and you're going to spend 5 minutes comparing brands of socks, anyway. So why the hell don't we all act like we know these things we clearly all know? Why are we willing to speed up and greatly increase our chances of dying horribly just to stop this stupid douche in his lame-ass Camaro from passing me before his lane ends?
Think about it this way - why in our ancestral past, and in fact, why anywhere in nature, would one animal overtake another, running? I can think of two scenarios right off the bat - they're a) going after some food or b) evading some predator. If you recognize that this is happening, what's a [read: the only] reasonable course of action for your limbic system to take in competitive situations that may mean life or death, especially where you may want a sudden burst of muscle strength? Rage circuitry, activate! Adrenaline++. Gaaah, you motherfucker! A mechanism that did this simply in response to any situation where another animal is trying to run past you would be an easy, effective response, and in nature, it would almost always be appropriate.
So what is the use of this information, supposing I'm even remotely correct?
This is an example of why I think Evolutionary psychology, while admittedly sort of ad hoc, can be useful. If you think this way habitually, you may catch yourself thinking irrationally in response to some vestigial mechanism in your brain that you or someone else has been able to point out and hopefully back up with some evidence or at least sound reasoning. If it's true (if its use always produces good results, then it probably is), you may learn to set aside emotions that might otherwise lead you to waste time and effort or risk harm, ultimately over nothing. Your brain makes mistakes, but other parts of your brain can correct those mistakes. Reason is our mind's tool for correcting them. Of course, you first have to recognize that they're mistakes. Evo-psych is one way of going about it, as I hope this helps to demonstrate.