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Does Similarity Imply Common Ancestry?

common ancestry

According to evolution, the species arose as a consequence of random events, such as mutations. Yet the biological world is full of repeated designs.

These so-called convergences are ubiquitous. And while a fundamental tenet of evolutionary theory is that similarity implies common ancestry, convergences are similarities found in more distant species — they cannot have arisen from a common ancestor. This falsifies the fundamental tenet that similarity implies common ancestry.

The tension can be further amplified by complexity and multiplicity. With similarities in different species that are highly complex, it can be difficult to explain how they evolved once, let alone twice in independent lineages. Add to this similarities that are found not twice, but a multiplicity of times, and you have what the press release of a new study out of Germany on the evolution of jawed vertebrates called “astonishing examples of repeated evolution.”

Photo: A side-necked turtle, Pelomedusa subrufa, by Johannes van Rooyen (Own work) [Public domain], via Wikimedia Commons.