Scientists May Reorganize the Animal Family Tree

A reshuffling of the animal kingdom may be necessary in light of new genetic findings -- not to lions, tigers or bears, but worms, a recent study suggests.

A team of international scientists including Albert Poustka from the Max Planck Institute for Molecular Genetics in Berlin have found that humans are more closely related to certain genera of marine worms than previously thought.

Biological classification of living things uses a system of six kingdoms (Animalia, Plantae, Fungi, Protista, Archaea, Bacteria). Each kingdom is then further broken down into eight major taxonomic ranks, phylums being the next in line. Scientific names (binomial nomenclature) are composed of the two most specific ranks, genus and species.

But thanks to the new findings, there may be big changes for that taxonomy.

The simple worms, Xenoturbellida and the acoelomorph, were thought to have evolved in linear fashion but by poring over their genome with intensive mathematical models, the researchers have found that these organisms may have evolved essentially in reverse fashion, finding it advantageous to shed more complex genes over time.

The implications, the team argues, are a potential new reorganization of the animal kingdom. One of the major evolutionary lines, the deuterostomes (“second mouth”) may need a new phylum. "Our research shows that Xenoturbellida and Acoelomorpha together form the fourth phylum which we have called 'Xenacoelomorpha'," explains Poustka.