You're in my seat

What is it about humans that makes us so territorial?

In college, there aren't assigned seats, yet did you notice that you always chose the same seat everyday?  And if someone was in "your" seat, you gave them a dirty look and called them a "jerk" under your breath.

At my first day at a TV station in Indianapolis, I went into the daily editorial meeting and sat down.  Not long afterwards, a producer came in and stood next to me.  I could feel him shooting a death glare my way.
Then he said, "Um, you're in my seat."
I said, "Oh, are these assigned seats?"
He replied, "No."  I looked around, and the other producers looked at me sheepishly.  They all knew he was being a little douche-y, but didn't want to say anything.  I got up and sat down in the seat next to him.

I find that this same kind of territorial nature exists at the gym.  At the YMCA I used to belong to, there were clipboards on each treadmill so you could sign up to use one.  This was helpful when the gym was really busy, but didn't apply to me because I worked out in the afternoons.  (Really the only advantage of being a morning reporter and getting up at 2 a.m.)  One day when I was working out, there were at least 10 open treadmills, but a woman came over to mine, and looked at the clipboard.
She scanned the list, looked at me, and said in an accusatory tone "Did you sign up for this treadmill?"
I looked around at all the empty ones, and said, "Are you serious?"
She huffed and walked away.

I notice the same thing at my new gym in Chicago.  Yesterday when I was on the treadmill, I saw the hairiest and sweatiest man I've ever seen walking towards me.  In my mind, I kept thinking, "Dear God, please don't let him come close to me."
Sure enough, even though there were plenty of empty treadmills, Mr. "I Don't Wear Deodorant" plopped on the one next to me.  The stench from his 'pits made me throw up a little in my mouth.  Today I noticed he was on the same treadmill.

Note to self?  Avoid any treadmill that's close to the 3rd one on the left, and on a first day of work, let everyone sit down before you to avoid an awkward encounter.