Classifying animals by anatomy may not be the best system, study finds

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As scientific knowledge advances, researchers often find that their old assumptions — even those that underlie centuries of work — no longer apply.

The same principle is at play when it comes to evolutionary trees, suggests a study in the journal Communications Biology. Researchers say the the method by which animals are sorted into evolutionary categories is flawed – and that it might be time to build new trees based on modern molecular science and geographic distribution.

Evolutionary trees have been around since Charles Darwin, who used the idea of ​​a “tree of lifeto map relationships between humans and primates. Other researchers have continued his work by developing what are called phylogenetic trees.

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But a recent look at the actual genetic relationships between organisms in these trees reveals that the anatomy-based classification system might be missing the mark. Trees have historically been mapped using morphology – the similarities and differences in the anatomy of organisms. Beneath the surface, however, creatures may be more genetically similar to organisms not on their traditional tree.

Although biologists have created “molecular trees” that map genetic similarities between species, they often completely contradict morphological classifications that group organisms based on their appearance. When the researchers compared the two types of trees and mapped them according to where the animals live, they found that those with molecular similarities were more likely to live next to each other than those that just looked alike.

“For example, tiny elephant shrews, aardvarks, elephants, golden moles, and swimming manatees all came from the same major branch of mammalian evolution – despite the fact that they look completely different from each other (and live very differently),” said Matthew Wills, a paleobiologist at the University of Bath and co-author of the study, in a press release. .

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These animals share more than molecular similarities – they all come from Africa. The researchers say the geographical distribution is a way to validate, and perhaps upset, evolutionary trees.

Research has also shown that convergent evolution – when unrelated species develop characteristics independently – is far more common than previously thought. The study implies that scientific methods continue to evolve, as do the ways in which we examine past attempts to make sense of animal relationships.

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