Actually, the theory of evolution does explain how all animal life developed. Though evolution doesn't explain how life itself began (the moment of inception), natural selection is sufficient to explain every form of animal life as we know it. Once you have microorganisms able to reproduce themselves, the rest is history, so to speak.... Played out over immense periods of time, the mechanism of natural selection is sufficient to explain biological diversity. Hundreds of millions of years is a difficult time frame to fathom. That's why our current degradation of the environment is so alarming. We're destroying ecosystems that took millions and millions of years to develop and that allowed us to develop and flourish as a species.

Religion in my opinion resulted from the traumatic gap that emerged between human consciousness and material reality. We cannot reconcile our minds and language with our finite, mortal bodies. We are painfully aware of our own mortality, individuality. Our consciousness does not have a home in this world. We need some way to sustain meaning accross the generations, independently of any particular individual. Thus, as humans, we build elaborate symbolic structures that offer our individual and collective consciousness a home. These symbols (which are fundamental to society, culture, and religion) offer us the security, stability, and lasting meaning that cannot be found in this world. They are often anxiously sustained by violence (both physical and psychological), since they create identity over against the world, others. Interestingly, at their most profound, the great religious traditions (Judaism, Christianity, Buddhism) actually challenge these symbolic structures, teaching us to set aside the futile attempt to secure an illusory symbolic identity and opening us up to the more uncanny, indeterminate reality of love and compassion. In other words, they make us aware of the reality actually in front of us.

Of course, if your talking about the origin of life itself, that remains a mystery...