Ok, I'll throw in my 2 cents (probably worth less). When I think about suffering, I see that ALL animal life suffers to some extent. The gazelle doesn't WANT to get eaten by the lion. It runs for its life, but doesn't always make it. The fly caught in the spider's web tries frantically to escape, until it is wrapped in sticky silk and its insides are turned to liquid. Ants war with one another, and enslave other ants. People die at the hands of other humans, as well as being killed by animals. Animals also die at the hands of humans.
Then there are natural disasters. We call them disasters, but, for the most part, they are simply the same natural phenomena that have shaped the earth for millenniums. We call them disasters because people or property get caught in the wrong place at the wrong time, and pay the price for this. Animals and humans suffer the same fate in these disasters.
The ONLY difference that I can see between humans and animals in all of this is humans' capacity for abstract thought. That is what seems to truly separate us from our closest animal relatives. With this capacity, we are able to wonder WHY. We are able to give names and identities to phenomena that we do not understand. Even many animals mourn the loss of a mate or child. But only humans have the ability to consider the meaning, if any, behind our experience. That's where god (or gods) comes in. A way to explain, not just natural phenomena like earthquakes, lightning, rain, and sun... but to explain our condition of being. Of course, once god is used as an explanation for these things, this could naturally progress to being a justification for things, with more suffering as a result. The story remains the same. God is used as the reason for suffering, whether at the hands of humans, or because of natural phenomena.
Now, where did this capacity for abstract thought, this ability so unique to Homo Sapiens Sapiens, come from?
I don't know.