It is known that the earth's magnetic field reverses every few millenia. was there any mass extinctions or anything that happened like that at the time.
You mean every few hundred millennia. And no, there is no connection. If any reversals coincided with a mass extinction, the connection is a correlation, not a causation.
soo I wonder...how is there evolution during the reversals, seeing as during a reversal almost all of the suns deadly radiation is let into the atmosphere..?
As for evolution, perhaps role reversals occurred with cavemen as their women became effected by such pole reversals.
no extinction, but evolution.