Thursday, 10 November 2022
Researchers at the University of Nottingham have solved an important piece of the animal evolution puzzle as their new study reveals that our ancient ancestors were more complex than originally thought.
Way back in our distant evolutionary history, animals underwent a major innovation. They evolved to have a left and right side, and two gut openings. This brought about a plethora of significant advantages in terms of propelling themselves directly forward at increased speed through the early seas, finding food, extracting nutrients, and/or avoiding being eaten. It was such a successful strategy that, today, we share our planet with a huge diversity of other animals with bilateral symmetry and two gut openings just like us. They include animals as diverse as starfish, sea cucumbers, elephants, humans, crickets, and snails. They also include an enigmatic group of very simple marine worms called Xenacoelomorphs, who lack many of the complex features of their fancier looking cousins.
For years, scientists have debated who is more closely related to who in this diverse collection of bilaterally symmetrical animals. Some experts argue that Xenacoelomorphs mark the first group to branch in that major jump in innovation from animals with circular body plans (e.g. jelly fish and corals) to bilateral symmetry. If this was the case, then the first bilaterian itself was also a very simple animal. Others argued for different placements of Xenacoelomorphs on the family tree.
However, a research team, led by Dr Mary O’Connell at the University of Nottingham has found that Xenacoelomorphs branch much later in time, they are not the earliest branch on the bilaterian family tree, and their closest relatives are far more complex animals like star fish. This means that Xenacoelomorphs have lost many of the complex features of their closest relatives, challenging the idea that evolution leads to ever more complex and intricate forms. Instead, the new study shows that loss of features is an important factor in driving evolution.
There are many fundamental questions about the evolution of animals that need to be answered... many parts of this family tree that are not known or not resolved. But what an exciting time to be an evolutionary biologist with the availability of exquisite genome data from the beautiful diversity of species we currently have on our planet, allowing us to unlock secrets of our most distant past.
The paper, titled ‘Filtering artifactual signal increases support for Xenacoelomorpha and Ambulacraria sister relationship in the animal tree of life’ has been published in the peer-reviewed journal, Current Biology. It details the application of a special phylogenetic technique to help in extracting signal from noise over deep time, showing increased support for Xenacoelomorphs being sister to ambulacraria (e.g. star fish) rather than being the deepest diverging of the bilateria.
The research team at the University of Nottingham will now explore other challenging family trees and other connections between genome changes and phenotypic diversity.
Notes to editors:
About the University of Nottingham
Ranked 32 in Europe and 16th in the UK by the QS World University Rankings: Europe 2024, the University of Nottingham is a founding member of the Russell Group of research-intensive universities. Studying at the University of Nottingham is a life-changing experience, and we pride ourselves on unlocking the potential of our students. We have a pioneering spirit, expressed in the vision of our founder Sir Jesse Boot, which has seen us lead the way in establishing campuses in China and Malaysia - part of a globally connected network of education, research and industrial engagement.
Nottingham was crowned Sports University of the Year by The Times and Sunday Times Good University Guide 2024 – the third time it has been given the honour since 2018 – and by the Daily Mail University Guide 2024.
The university is among the best universities in the UK for the strength of our research, positioned seventh for research power in the UK according to REF 2021. The birthplace of discoveries such as MRI and ibuprofen, our innovations transform lives and tackle global problems such as sustainable food supplies, ending modern slavery, developing greener transport, and reducing reliance on fossil fuels.
The university is a major employer and industry partner - locally and globally - and our graduates are the second most targeted by the UK's top employers, according to The Graduate Market in 2022 report by High Fliers Research.
We lead the Universities for Nottingham initiative, in partnership with Nottingham Trent University, a pioneering collaboration between the city’s two world-class institutions to improve levels of prosperity, opportunity, sustainability, health and wellbeing for residents in the city and region we are proud to call home.
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