of course waves have existed long before humans existed.
And yes, radio waves existed long before the invention of radio. Yes, science have allow people to harness them through various technology.
You are stating the obvious, but you really you don’t understand, that scientists already know this, and you would know too if you bother to learn physics.
What do you think electromagnetism are?
They are electromagnetic waves. They are radiations. EM waves include radio waves, microwaves, X-ray, gamma ray, ultraviolet, infrared, visible light. How they differ from each other, are known by the respective ranges of their wavelengths.
Radiation is emission or transmission of waves (or the radiation can be emission of particles, eg photons, radioactive decay, etc), which are propagated through space or through medium.
Yes, they can be harnessed, so the source of transmission of these waves, can be man-made, but there are natural sources of emissions, such as from radioactive elements, eg uranium, or many of waves come from the sun itself. The sun not only radiated heat, light, and ultraviolet, but also gamma rays, radio waves.