Some of the most interesting evidence for ancient life does not look like a fossil. It can look like a wrinkle. Researchers studying Jurassic rocks in Morocco have identified unusual sedimentary structures that may record microbial communities living on the seafloor roughly 180 million years ago. That would not, by itself, be particularly surprising. Microbial life was already widespread in Earth's oceans. The strange part is where these structures formed. The sediments appear to have accumulated in relatively deep water — around 200 metres below the ancient ocean surface. That raises an important question. If sunlight was severely restricted at that depth, what was providing the energy for these organisms? One possibility is that they were not using sunlight at all. They may have been running an ecosystem on chemistry. And if that interpretation is correct, the discovery provides another reminder that the ancient ocean was probably far more biologically diverse — and far stranger ...
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