Franken food and roundup

I learned the other day that it is possible to have wheat with a gene that is resistant to the weedspray "roundup" as a component of it so as to make it resistant to the weedspray. It seems crazy to me to change the path of evolution, change the format of a food that has fed mankind for thousands of years.What havoc will be created by making the change? The body has evolved over thousands of years and become acclimatized to consume food prepared in a particular format. So what happens when the food is different?

Have studies been done of the long term effects of a change in diet?

Is it really needed to feed humans with an anti-roundup gene?

Article on roundup ready wheat