“How does soul interface with body”.

Well as the 'soul'has never been identified, tracked, measured or even fully explained as a concept.....I would argue that it is what we call concsiousness.

The subject is huge, with many new insights over the last 10 years. You are your brain and one of it's functions, amongst many, is conciousness. eg breathing is not concsious.
The human race, as far as we know, is the animal with the highest developed area of consiousness but research is discovering a sliding scale of this area in other animals we share the planet with.
All life forms are related and it will be possible at some point to track the evolutionary development of consiouness over geological time.