Where have you gotten your information about the intensity of solar radiation over time? The studies I have seen project some degree of solar variation, and some degree of fluctuation in terrestrial temperature as a result of this and other factors. However, I have seen nothing that indicates that temperatures on Earth at the time life is presumed to have begun (about 3 to 3 1/2 billion years ago) were as hot as you claim.

The sun, being a medium-size yellow star, has a long and relatively stable life cycle. Solar radiation reaching Earth at that time was probably not too different from today.