Petroglyphs are carved in a material called rock varnish, the origins of which have been debated for years. Now, scientists argue it’s the result of bacteria and an adaptation that protects them from the desert sun’s harsh rays.
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Petroglyphs are carved in a material called rock varnish, the origins of which have been debated for years. Now, scientists argue it’s the result of bacteria and an adaptation that protects them from the desert sun’s harsh rays.