I can't prove it but if you have a better theory which is empirically testable and repeatable I'm all ears.
I can't repeat the dawn of life on earth but we can observe the development of life as the mutual arising of the nervous system alongside the skeleton, muscles and cartilage - in cases where life can be categorised in such a fashion. I can observe it in my own body as I grow. If I arrived on this earth with my current physical appearance as I am now but with no control at all over my body which I slowly gained control of, or I arrived as a fully functioning nervous system around which bones and cartilage began to develop I may see some point in you asking if 1 or 2 came first, even have a good answer for you. As it is it seems like an arbitrary dichotomy which isn't really of much use to anyone. As I play the guitar, practice kung fu or explore how to sharpen steel on stone there is a mutual arising of physical development alongside neurological control.
The use of 1 develops 2, but 1 is not possible without 2. I would contend your question is a false dichotomy.
I'm not sure what your theory on the origins of life and humanity are but if you could explain them whilst answering your own question about whether 1 or 2 came first, without the imaginings of mutual arising, and only using empirical repeatable evidence without any imagination I'd be keen to hear.