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Most of our evolutionary trees may be wrong

An evolutionary tree, or phylogenetic tree, is a branching diagram that shows the evolutionary relationships between different biological species based on similarities and differences in their characteristics. Historically, this was done using their physical characteristics – the similarities and differences in the anatomy of different species.

However, advances in gene technology are now allowing biologists to use genetic data to decipher evolutionary relationships. According to a new study, scientists have found that molecular data leads to very different, sometimes overturning, results of centuries of scientific work in classifying species by physical characteristics.

New research led by scientists at the University of Bath’s Milner Center for Evolution suggests that defining the evolutionary trees of organisms by comparing anatomy rather than genetic sequence is misleading. The study was published in the journal Communication biology On May 31, 2022, it shows that we often need to tear down centuries of academic work classifying living things according to their form.

“This means that convergent evolution has been fooling us – even the smartest evolutionary biologists and anatomists – for over 100 years!” – Matthew Wells

Since Darwin and his contemporaries in the nineteenth century, biologists have attempted to reconstruct the “family trees” of animals by carefully examining differences in their anatomy and structure (morphology).

However, with the development of rapid genetic sequencing techniques, biologists are now able to use genetic (molecular) data to help piece together the evolutionary relationships of species very quickly and inexpensively, often proving that organisms we once thought closely related to reality belong to a completely different set of tree branches.

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For the first time, scientists in Bath compared phylogenetic trees based on morphology with those based on molecular data and plotted them according to geographic location.

They found that animals grouped by molecular trees lived together more geographically than animals grouped using morphological trees.

“It turns out that many of our evolutionary trees are wrong,” said Matthew Wells, professor of evolutionary paleobiology at the University of Bath’s Milner Center for Evolution.

“For more than a hundred years, we’ve categorized organisms according to their shape and grouped them together anatomically, but molecular data often tell a slightly different story.

“Our study statistically proves that if you build an evolutionary tree of animals based on their molecular data, it better fits the geographic distribution.

“The place where things live – their biogeography – is an important source of evolutionary evidence that was familiar to Darwin and his contemporaries.

“For example, shrews, pigskins, elephants, golden moles, and swimming manatees all come from the same large branch of mammalian evolution—even though they look very different from one another (and live in very different ways).

“The Molecular Trees put them together into a group called Afrotheria, or whatever that’s called because they all come from the African continent, so the group matches biogeography.”

Molecular phylogenetic trees show that elephant shrews are more closely related to elephants than to shrews. Credit: Danny Ye

The study found that convergent evolution — when a trait develops separately in two groups of organisms that are not genetically related — is more common than biologists previously thought.

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Professor Wells said: “We already have many famous examples of convergent evolution, such as flight that evolve separately in birds, bats and insects, or complex camera eyes that evolve separately in squid and humans.

“But now, with the molecular data, we can see that convergent evolution is happening all the time — things that we thought were closely related are often farther down the tree of life.

“People who make a living as imitators often don’t identify with the celebrities they represent, and people within a family aren’t always the same — it’s the same with evolutionary trees too.

“This proves that evolution keeps reinventing things, coming up with a similar solution each time the problem is found on a different branch of the evolution tree.

“This means that convergent evolution has been fooling us – even the smartest evolutionary biologists and anatomists – for over 100 years!”

Jack Auston, co-author and first author of the paper, said: “The idea that biogeography could reflect evolutionary history was a big part of what drove Darwin to develop his theory of evolution through natural selection, so it’s pretty surprising that he didn’t…a simple way. Extremely.[{” attribute=””>accuracy of evolutionary trees in this way before now.

“What’s most exciting is that we find strong statistical proof of molecular trees fitting better not just in groups like Afrotheria, but across the tree of life in birds, reptiles, insects, and plants too.

“It being such a widespread pattern makes it much more potentially useful as a general test of different evolutionary trees, but it also shows just how pervasive convergent evolution has been when it comes to misleading us.”

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Reference: “Molecular phylogenies map to biogeography better than morphological ones” by Jack W. Oyston, Mark Wilkinson, Marcello Ruta and Matthew A. Wills, 31 May 2022, Communications Biology.
DOI: 10.1038/s42003-022-03482-x