In 1927, the American Ivan Wallin described symbiosis as an “engine of novelty”. He argued that symbiotic bacteria transformed existing species into new ones, which was the fundamental means through which new species arose. Lynn Margulis echoed his views in 2002, claiming that the creation of new symbioses between distinct organisms – which she called symbiogenesis – has been the main force behind the origin of new species. To her, the kinds of relationships you’ve seen so far in this book were not just pillars of evolution, but its very foundations. She failed to make her case, though. She
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