Humans were not meant to die on earth. In order for us to appreciate, benefit and learn all we can from physical life, we seemingly have to rediscover what we knew before, only in physical ways, and discover how to return to God. The reason humans die physically is because they have fallen away from nature and violated its laws. To survive, humans must relearn the harmonic balance with nature. This is the next goal for humanity.
All souls are equal at the spirit level.
The spirit doesn't evolve, the personality of the soul does. Humans have a group soul, but have also evolved to have an individual conscious. Animals have only a group soul and reincarnate in groups. The races of humanity are actually personality clusters. Nations and cities also form their own clusters.