As far as I can see it, any predictions about future evolution can only be as strong as our predictions on what the environment and other relevant factors will be like in the future. Anything else is just speculation. We might be able to see why a particular species has evolved when we look back through evolutionary history, but even then we can be wrong on occassions.
A goal or purpose for life is propogating life itself, I think that's it really. If life had any other 'purpose' would suggest intelligent design. I don't think that because life is the sole purpose of life necessarily means that brain development in humans is a foregone conclusion. Perhaps, for example, we develop a mechanism - such as lungs or gills - that allow only humans to process high levels of nitrogen, or something, over other species of animals. More simply, maybe a virus will wipe out all traces of human life. Would this mean the virus had the bigger brain, that they out-smarted us?
