Elephant Shrew

Convergent evolution fools us: most of our evolutionary trees could be wrong

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

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 features – the similarities and differences in the anatomy of different species.

However, advances in genetic technology allow biologists to use genetic data to decipher evolutionary relationships. Scientists find that the molecular data leads to many different results, sometimes negating centuries of scientific work classifying species by physical characteristics, according to a new study.

New research led by scientists at the Milner Center for Evolution at the University of Bath suggests that determining evolutionary trees of organisms by anatomy rather than comparing gene sequences is misleading. The study, published in the journal Communication biology on May 31, 2022, shows that we often have to overthrow centuries of scientific work that classified living things based on how they look.

“It means convergent evolution has been fooling us – even the brightest evolutionary biologists and anatomists – for over 100 years!” † Matthew Wills

Since Darwin and his contemporaries in the 1800s, biologists have attempted to reconstruct the “family trees” of animals by carefully examining the 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 construct evolutionary relationships for species very quickly and cheaply, often proving that organisms we once thought were closely related. , actually in completely different branches of the tree.

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

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

Matthew Wills, Professor of Evolutionary Paleobiology at the Milner Center for Evolution at the University of Bath, said: “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.

“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.

“Where things live — their biogeography — is an important source of evolutionary evidence with which Darwin and his contemporaries were familiar.

“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’re all from the African continent, so the group matches the biogeography.”

Molecular evolutionary trees Elephant shrew

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

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

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

“But now with molecular data, we can see that convergent evolution happens 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 their living as lookalikes are usually unrelated to the celebrity they’re impersonating, and individuals within a family don’t always look alike — it’s the same with evolutionary trees, too.

“It proves that evolution keeps reinventing things, and every time the problem arises in another branch of the evolutionary tree, it comes up with a similar solution.

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

dr. Jack Oyston, Research Associate and lead author of the paper, said: “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’s not really directly considered as a way to get 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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