Alan doesn’t believe that there are any other proposed explanations to rival ‘evolutionary theory’. At least none that so effectively account for the facts.
It is often said that there is no single theory of evolution, there are a group of mutually consistent theories. Be that as it may, I think we all understand the point Alan is making.
Evolution is a process whereby life has somehow emerged from a lifeless physical world and there is no overall teleology involved in its diversification. The reproductive processes produce a natural variety of forms which can take advantage of previously unoccupied niches. The basic sequence of events from primal to present are: lifeless minerals, water systems and gaseous atmosphere, followed by the arrival of simple prokaryote life forms, followed by multicellular organisms. Life is solely the product of physical and chemical processes acting on lifeless matter.
In this view life is nothing special, it just occurred because physical matter chanced to arrange itself in a particular way. And consciousness is just a by product of life.
But I suggest that there is an alternative way in which life as we perceive it could have come about.