I am interested in theories.
A theory does not need to be solid - theories are always works in progress.
One area that interests me is around brain development and evolution. It is observable through dissection that there is similarity across animals. Crocodile brain structure is found in more recently evolved animals. Crocodiles reached an evolutionary end. They evolved to perfection within their environment and so have remained where they are. Still we must have shared common ancestors and the same structures do the same job in our brains. They even look the same. Inside the human brain is a section like in a crocodile brain.
This old brain structure fulfills the same functions in horses and humans. It deals with satisfying basic needs like protection of territory, food and sex. Crocodile stuff. In horses are further brain structures dealing with sociability and higher functions not available to crocodiles. Again brain dissection reveals there are sections of the horse brain are replicated in the human brain and they do the same job.
Finally in human brains there are further brain sections not present in crocodiles or horses. These deal with higher intellectual functions.
Comparing brains in this way is crude. Yet to me is compelling. From it we can conclude we are evolved from common ancestors. We can conclude our brains are modular not of singular design.
I think that the interaction of the various inheritances is somewhat different in different people. Maybe under stress we become more crocodile like? I often think the crocodile is dominant in some people. Sometimes I think the horse and the human are almost absent. Crocodile people frighten me!