I just gave you an example of one way it could be measured objectively. As far as emotion goes, I disagree that it should be the basis for determining the value of something for the reasons you already pointed out. But if I were to take that position, I think it would still apply for my example. The foster mother would promote a much greater amount of positive emotion (love) in the children she cares for than would a serial killer chasing them around with a big knife (fear).

Would you be willing to prove the depth of that conviction? Think of the thousands of maggots that could grow and reproduce off of just your one single body. Yet here you sit typing on the internet while millions of flies, rats, bacteria, etc. starve to death. Shame on you. ;)

And that intelligence also affords us the opportunity to use that in ways which would benefit both parties. If we were to discover tomorrow that a doomsday comet will soon hit the earth, we alone are capable of attempting to ensure the survival of all species. Animals would not and could not make the same attempt.

I would argue that there is in fact a way to objectively determine the value of a life; by comparing and contrasting the effects one life has in relation to others. An easy example would be comparing a serial killer to a foster mother. One decreases the total amount of life in the population as well as ensuring the loss of his own life when he is caught and executed, while the other protects life and encourages those lives to be successful and thus spread more life.

And not much else. How many herds of deer have rallied to save an endangered species lately? Humans care about a great deal more than just their own lives and that of their families. So if caring is your measurement of worth, we have more it.

This is silly, they don't use roads. I'll play along anyways. Train a bunch of chimps to drive, stick them in cars, observe the increased level of blockage. If all things were equal in regards to road use, humans would cause much less trouble than they.

The fact that this question is asked in the first place provides the answer. Animals would not consider any such thing. Humans have the ability to act in an altruistic manner. We have the unique position of being able to safeguard and foster all life in general; assuming that is what we choose to do. A human can be seen to put forth effort in maintaining the well-being of a pet cat for example. Reverse the roles and the same could not be said under most circumstances. One human life may lead to the growth of not only more humans, but animals as well. An animal on the other hand, has neither the compulsion nor the intellectual context in which to put forth any effort which does not benefit itself or it's offspring.