Ever since Darwin published and popularized the idea of evolution, researchers began building evolutionary trees — also called phylogenetic trees — branching diagrams that depict the evolutionary relationships between different species that share different characteristics.
It’s a very useful and simple tool, except it can be quite wrong, the authors of a new study say.
Genes don’t lie
If you were a biologist who wanted to classify animals in the 19th or 20th century, your options were limited. You could study the ecosystem and the animal’s role in it, describe the morphological features of the species in detail, but that was about it — you had to rely a lot on things that looked like other things.
But in more recent years, the advent of genetic analysis has opened new doors for classifying species. As rapid genome sequencing became relatively cheap and readily available, researchers had new tools for seeing which species were related to which, and they began to notice that sometimes things weren’t as expected.
Sometimes one species can turn out to be different types of, or species thought to be closely related, may in fact be very different. Matthew Wills, Professor of Evolutionary Paleobiology at the Milner Center for Evolution at the University of Bath, says that “it turns out we got a lot of our evolutionary trees wrong.
“For over a hundred years, we’ve been classifying organisms based on how they look and are anatomically constructed, but molecular data often tells us a very different story.”
The problem is that rather unrelated creatures often evolve in somewhat similar ways. For example, if you only look at flies, you might be tempted to believe that bats and birds are closely related – when that’s no less true. Of course any biologist can see that bats and birds are very different, but sometimes the differences are more subtle and can be difficult to see. For example, many insects exhibit similar mouthparts, even though this is not the case to be closely related† This is called convergent evolution: the independent evolution of similar traits in different groups of animals.
In the new study, Wills and colleagues compared 48 pairs of morphological and molecular data, and found that: convergent evolution is more common than previously believed, and as a result, several “traditional” evolutionary trees are not as accurate as previously believed.
“Our study statistically proves that if you build an evolutionary tree of animals based on their molecular data, it often fits their geographic distribution much better,” Wills said in a press release. “Where things live — their biogeography — is an important source of evolutionary evidence known to Darwin and his contemporaries.”
“For example, little elephant shrews, aardvarks, elephants, golden moles and swimming manatees all come from the same major branch of mammalian evolution – despite the fact that they look completely different (and live in very different ways). Molecular trees have put them all together in a group called Afrotheria, so named because they are all from the African continent, so the group matches the biogeography.”
In addition to helping biologists better understand these biological relationships, this study also shows that we should not rely on things that are similar. Plus, it shows that evolution doesn’t always make new things – instead, it seems to tend to produce somewhat similar things over and over again. Jack Oyston, research associate and lead author of the article, concludes:
“The idea that biogeography can reflect evolutionary history was a big part of what led Darwin to develop his theory of evolution through natural selection, so it’s quite surprising that it wasn’t really viewed directly as a way of assessing the accuracy of evolutionary history. test trees earlier this way.”
“Most excitingly, we find strong statistical evidence that molecular trees fit better not only in groups like Afrotheria, but also in the tree of life in birds, reptiles, insects and plants.”
“It’s such a pervasive pattern, which makes it much more potentially useful as a general test of different evolutionary trees, but it also shows how pervasive convergent evolution has been when it comes to misleading us.”
The study was released in Communication biology†
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