I'd never seen this information posted anywhere, so I thought I'd share it with everyone. Hopefully it'll be new to some people (and hopefully it's accurate).
If you've been playing Tremulous for a while then you've probably noticed that Aliens can receive multiple evos for a single kill. So how much is that human worth, anyway? It depends on the weapons and upgrades he's carrying. The cutoff points, based on information in the source code, are 300 credits and 600 credits.
0 to 300 credits: worth 1 evo
301 to 600 credits: worth 2 evos
601 and higher: worth 3 evos
What does this mean for humans? Be careful with what you purchase! A simple shotgun with light armor is very cheap and effective, and gives the aliens only 1 evo if you die. But if you include a helmet then you're worth twice as much to them!
The mass driver, all by itself, is worth 2 evos to the aliens. The lasgun is only worth 1 evo by itself, but if you add ANY kind of armor then you're worth twice as much to the aliens. The battlesuit, at a whopping 400 credits, means that you're worth 2 evos unarmed and 3 evos with any weapon larger than shotgun.
Conclusion? Be careful when carrying expensive equipment! Also, give serious consideration to using cheap weapons (rifle, shotgun, painsaw). An upgrade may give you a a 20% boost in killing power, but a 100% boost to Alien evolution!