Phylogenomics research confirms that sponges are the oldest animals

A sea sponge of the species Aplysina aerophoba
A sea sponge of the species Aplysina aerophoba

An article published in the journal “Current Biology” describes a research that through a cutting-edge statistical analysis tested evolutionary models commonly used in the field of phylogenetics to understand which is the most ancient group of animals that appeared on Earth. A team of researchers concluded that it’s the group of sponges (photo ©Yoruno), confirming some previous research and contradicting others that indicated ctenophores as the oldest in a dispute that’s been going on for years.

Advances in genetic analysis have greatly improved the understanding of the relationships among the various animal families, yet there’s still much to be clarified. Increasingly in these cases, technical terms are used related to new technologies that brought these advances but also greater complexity in data analysis and in the understanding of research that take advanteg of the continuous changes.

Computers have been used for a long time to perform biological data analysis, that’s why we talk about bioinformatics. The genetic researches based on it for data processing are part of a new branch of molecular biology that was called genomics. In recent years, genomics was also applied to phylogenetics, the study of the various ramifications of a group of organisms, leading to the birth of phylogenomics.

Phylogenomic research was already conducted to try to understand which is the most ancient group of animals that appeared on Earth with different results. According to the one described in an article published in the journal “Nature Ecology & Evolution” it’s the group of ctenophores – phylum Ctenophora – but in recent years there was a kind of flip-flop in this field. The different conclusions are due to the different methods of analysis, which have become more sophisticated over the years and are based on larger amounts of data.

In this new research the latest developments of statistical techniques were applied to the datasets used in the field of phylogenetics in the study of the evolution of the first animals. Various possible models were created that describe different evolutionary stories in which sponges or ctenophores emerged first with the consequence that there are different relationships between the various groups of animals.

In the test carried out, the researchers evaluated which hypothesis between sponges or ctenophores being the first animals better described the available datasets. The result is that the models that best describe the available datasets favor sponges hypothesis while the models that fail to describe the datasets favor ctenophores.

According to the researchers this test is evidence that closes the discussion but in these cases it’s difficult to establish it without further confirmation. Unfortunately it’s impossible to look for evidence in fossils because ctenophores have gelatinous bodies so their fossils are rare. Scientists have to resort to indirect research and the consequence is that each new study can offer different conclusions and it’s not known if a final word will ever arrive.

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