Sunscreen, as we know it, is barely 100 years old (see https://pubmed.ncbi.nlm.nih.gov/33583116/ https://pubmed.ncbi.nlm.nih.gov/33583116/) and we have a lot of

Sunscreen, as we know it, is barely 100 years old (see https://pubmed.ncbi.nlm.nih.gov/33583116/ https://pubmed.ncbi.nlm.nih.gov/33583116/) and we have a lot of information up to that point. We can also deduce from many sources that humanity did not just "managed to reproduce before keeling over".