Disappointment about our own species

Where would you begin? GR? QM?
I don't think I'd start at the abstract level, attempting to define and describe "science." I'd pick some Stone Age technology that the fellow is familiar with (flint napping, starting a fire, brewing an alcoholic beverage, throwing a spear) and try to identify the specific basic principles of the universe that make this particular technology work reliably.
I am confident that any native warrior is familiar with trajectories, even as they don't understand the dynamics. It should not be hard to teach gravity, as a start.
There you go, good idea.
As a substitute teacher, I taught photography a for a while. I started with the question "what is photography" and then explained the various parts of a camera and their function in the system, all the while demonstrating each function, such as focal point, shutter speed, aperture control, composition. I must have done something right, after the second session I tasked the students with taking a picture of their favorite subject and "show and tell" how this picture was taken and what the main subject was. The improvement in all respects was noticeable and I had several compliments from the students, because they were proud of their work. It seems that this gradual introduction of fundamentals of photography had an immediate positive effect. Understanding the fundamental principles of anything seems to help in "analyzing" the subject and make "knowledgeable decisions" of how to approach the problem.
Great! You know what you're doing.