The earliest known relative of humans is… a sponge?

Scientists have determined that humans likely descended from sponges that lived in early oceans 750 million years ago. According to the researchers, these creatures are the eldest ancestors of all animals.

This new discovery challenges the previous belief that comb jellies are the oldest members of the animal kingdom. Researchers from the University of Bristol used a new method to statistically test evolutionary models for accuracy. They found that the more precise evolutionary models indicated that sponges are at the root our lineal descent.

Professor Davide Pisani is the lead author of the study.

“Phylogenomics, the use of genomic data in phylogenetics, is a relatively new science,” explained Professor Pisani. “Evidence for comb jellies as the earliest branching animal lineage first emerged in 2008, a decade ago, in the first, large-scale, phylogenomic analysis of the animal phyla. We have now better analytical tools and data and this study seriously challenges the accepted status quo.”

Professor Pisani pointed out that sponges and comb jellies represent completely different evolutionary backgrounds of animal organ systems such as the digestive and nervous 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,” he explained.

The prehistoric sponge was a filter feeder with no complex organs. While it is not clear what the first-ever animals looked like, Professor Pisani said it was most likely a lot simpler than modern sponges and possibly resembled a blob.

“I found it pretty exciting to find that something as simple as a sponge might have kick-started modern ecosystems,” said Professor Pisani.

The research is published in the journal Current Biology.

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By Chrissy Sexton, Earth.com Staff Writer