Most of our evolutionary trees could be wrong

Elephant shrews are more closely related to elephants than shrews, according to molecular evolutionary trees.

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

However, advances in genetic technology now allow biologists to use genetic data to decipher evolutionary relationships. According to a new study, scientists are finding that molecular data lead to vastly different results, sometimes overturning centuries of scientific work in classifying species by physical traits.

New research from scientists at the University of Bath’s Milner Center for Evolution suggests that determining the evolutionary trees of organisms by comparing anatomy rather than gene sequences is misleading. The study, published in the journal Communications Biology May 31, 2022 shows that we often need to overturn centuries of scholarly work that classified living things based on their appearance.

“That means convergent evolution has fooled us – even the smartest evolutionary biologists and anatomists – for over 100 years!” — Matthew Wills

Since Darwin and his contemporaries in the 19th century, biologists have attempted to piece together 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 formerly thought to be intertwined actually belong to completely different organizations. tree branches.

For the first time, Bath scientists compared evolutionary trees based on morphology with those based on molecular data, and mapped them according to their geographic location.

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

Matthew Wills, professor of evolutionary paleobiology at the Milner Center for Evolution at the University of Bath, said: “It turns out that we got a lot of our evolutionary trees wrong.

“For over a hundred years we have classified organisms based on their appearance and anatomical assembly, but molecular data often tells us a rather different story.

“Our study statistically proves that if you build an evolutionary tree of animals based on their molecular data, it often matches their geographical distribution much better.

“Where things live – their biogeography – is an important source of evidence for evolution that was familiar to Darwin and his contemporaries.

“For example, the tiny elephant shrews, aardvarks, elephants, golden moles and swimming manatees all descended from the same large branch of mammalian evolution – despite the fact that they look completely different from each other. (and live in very different ways).

“The molecular trees put them all together in a group called Afrotheria, supposedly because they all come from the African continent, so the group fits the biogeography.”

Molecular evolutionary trees Elephant Shrew

Molecular evolutionary trees show that elephant shrews are more closely related to elephants than to shrews. 1 credit

The study found that convergent evolution – when a characteristic evolves separately in two groups of genetically unrelated organisms – is much more common than biologists previously thought.

Professor Wills said: ‘We already have many famous examples of convergent evolution, such as flight evolving separately in birds, bats and insects, or complex camera eyes evolving separately in squid and insects. 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 often turn out to be far apart on the tree of life.

“People who make a living as look-alikes aren’t usually tied to the celebrity they impersonate, and individuals within a family don’t always look alike – that’s also the same with evolutionary trees. .

“It proves that evolution keeps reinventing things, coming up with a similar solution each time the problem is encountered in a different branch of the evolutionary tree.

“That means convergent evolution has fooled us – even the smartest evolutionary biologists and anatomists – for over 100 years!”

Dr Jack Oyston, research associate and first author of the paper, said: “The idea that biogeography can reflect evolutionary history was largely what prompted Darwin to develop his theory of evolution by natural selection, so it’s quite surprising that it hasn’t really been considered directly as a way to test the[{” 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.”

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

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