How did humans avoid skin cancer and sunburns in the past when there weren’t houses ?

They used mud or charcoal on their skin, or they stayed in the shade, or wore clothing that protected them from the sun. You should watch Naked and Afraid, that will give you some idea of what life with out sun screen is like. 

I have fair skin too. I have to apply sunscreen every 2-3 hours when I'm in the sun for long periods of time. 

White people with fair complexion originally lived in the extreme northern hemisphere where the sun intensity was low.  They were also outside all year round, so they had time to build up a summer tan as days lengthened in spring. 

They didn't.   And shade has existed LONG before man.

maybe they used some kind of lotion to avoid sunburns