Why do animal testing

Reports today that the FDA is looking at human foods to see if they have been contaminated by the pet foods being recalled. Some of the pet foods under recall have been fed to pigs and chickens. But it turns out that we do not know if this chemical is bad for humans. Animal testing has been performed and it has made animals sick. But the effects on humans remains unknown. So my question is why test on animals in the first place? Why not test on humans? Is it some kind of cruel punishment to do so? And if so,why? Can anyone tell me why its cruel to test on humans but not cruel to test on animals? What makes us as people more special than animals? Religious people, myself included, believe God created heaven and the earth. Yet very few religious people are strong environmentalist. And even fewer are animal rights activist. Why? Would it not make sense to protect all that God has created? Humans, animals and the environment. And how can a religious zealot be anti-abortion but yet pro-war and pro-death penalty? I favor the death penalty but again I do not have a problem testing chemicals on people either. Why not use prisoners? People in prison with life sentences, let them do some good for society, test chemicals on them and see how they react. At least they would be able to say its hurts or I don't feel good. Animals just cry out in pain and then get stuck back in small cage to die in agony. The alternative if prisoners did not participate in testing we could send these life term prisoners to Iraq, we need more troops over there anyway. So what if they escape, where are they going to go?