Do humans really mark the pinnacle of evolution, or do viruses? While we’ve evolved along a pathway of ever-increasing complexity, viruses have streamlined, successfully jettisoning all but a handful of essential genes, research published in Science Advances in September suggests.

Gustavo Caetano-Anolles and his colleagues at the University of Illinois reached this conclusion after pioneering a new way to map the microbial family tree. Viruses did not evolve first, they found. Instead, viruses and bacteria both descended from an ancient cellular life form. But while – like humans –  bacteria evolved to become more complex, viruses became simpler.

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