Which of the following provides key evidence that 3.5-billion-year-old stromatolites indicate the presence of life on earth at that time? which of the following provides key evidence that 3.5-billion-year-old stromatolites indicate the presence of life on earth at that time? microfossils found within stromatolites that appear to be individual fossilized microbes the layered structure of the stromatolites because layering can be produced only by life the similarity in structure between the stromatolites and bacterial mats that still live today the presence of living bacteria in stromatolites.