Even with all our adaptations we still get cancer from sunlight on a regular basis.
It is easy to understand why, UVB light is near ionizing has enough energy to damage human DNA causing cancer.
Below UVB there is not enough energy to cause DNA damage through a known mechanism except heating.
Heating directly related to power absorption, a 1500 watt microwave will cook you a 300 milliwatt pulsing microwave transmitter will not heat your flesh enough to cause any damage.
We have a pretty good grip on how various frequencies of radiation affect human biology and cell phone emissions are orders of magnitude lower power that whats needed to heat flesh enough to cause damage you literally get more heat directly from the phone being warm than RF absorption.
I don't propose we stop looking for any possible biological activity due to microwave (or any other spectrum) but repeated test have not shown this to be the case and to do so would mean there is some new mechanism for this to do so.
If you are scared of 300 milliwatt RF emissions I would be more scared of multi-watt LED light emissions due to higher energy levels (terahertz vs gigahertz).