The new research reveals the humble sponges have the most ancient lineage.
New research led by the University of Bristol has resolved evolutionary biology's most-heated debate, revealing it is the morphologically simple sponges, rather than the anatomically complex comb jellies, which represent the oldest lineage of living animals. Recent genomic analyses have "flip-flopped" between whether sponges or comb jellies are our deepest ancestors, leading experts to suggest available data might not have the power to resolve this specific problem. However, new research led by the University of Bristol has identified the cause of this "flip-flop" effect, and in doing so, has revealed sponges are the most ancient lineage. Professor Davide Pisani of Bristol's Schools of Biological and Earth Sciences led the study, published today in Current Biology , with colleagues from the California Institute of Technology (Caltech - USA), Ludwig-Maximilians-Universität (LMU), Munich (Germany), and other institutes around the world, which analysed all key genomic datasets released between 2015 and 2017. Commenting on the breakthrough research, Professor Pisani said: "The fact is, hypotheses about whether sponges or comb jellies came first suggest entirely different evolutionary histories for key animal organ systems like the nervous and the digestive systems. Therefore, knowing the correct branching order at the root of the animal tree is fundamental to understanding our own evolution, and the origin of key features of the animal anatomy." In the new study, Professor Pisani and colleagues used cutting edge statistical techniques (Posterior Predictive Analyses) to test whether the evolutionary models routinely used in phylogenetics can adequately describe the genomic datasets used to study early animal evolution.
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