The discussion about which animal was the first on the Ground, continued for over a century.
It is believed that the first were sea sponges, because of their inherent biological simplicity of the structure. But a new genomic study suggests that the sponges were preceded by the ctenophores, even though they are more complex life form.
“A modern method that scientists use to phylogenomic research is the analysis of large volumes of genetic data, which then build relationships. This works very well in 95% of cases, but leads to irreconcilable differences in the remaining 5 percent,” said biologist Antonis Rokas of Vanderbilt University.
These irreconcilable differences can be seen in various studies of competing groups of scientists, whose conclusions contradict each other. A number of researchers argue that sponges are the most ancient branch of the family tree of animals, a number of scholars are of the opinion that the Ctenophora. Now to find out why the studies give such conflicting results, Rokas and his team have developed a new method of comparison of genes shared between the different animals They tested the approach on 18 controversial relationships in the field of evolutionary biology between animals, fungi and plants.
“In this analysis we used only those genes that are common to all organisms. The trick is to explore sequences of genes from different organisms to find out who they identificeret as their closest relatives,” — said Rokas.
Scientists found that the more genes shared, the more likely it is that the animal is a relative of another. The researchers found that the ctenophores show a much more common genes than a sea sponge. Thus, the results of a new study suggest that the first animals were ctenophores.
Scientists also explained the difference in results from different studies. According to them, this is due to “very strong” genes, which affect the statistics overall. The exclusion of these genes from the analysis avoids such errors.
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