Evolution from Worms: 70 Percent of Human Genes Trace Ancestry to the Acorn Worm

Researchers have sequenced the genomes of two species of small water creatures called acorn worms, and have found that humans may have more in common with them than first thought. It turns out that humans share about 70 percent of their genes with these tiny worms.

About 650 million years ago, a great variety of animals evolved during a time period called the Cambrian explosion. This evolutionary explosion resulted in several new animal body plans, and changed life on Earth forever. Thanks to the genome sequencing of multiple contemporary animals of the deuterostome group, scientists are now unveiling aspects of long-lost ancestors of this diverse group of animals.

Acorn worms are actually marine creatures that live on the ocean floor and feed by filtering a steady flow of sea water through slits in the region of their gut between the mouth and esophagus. These slits are distantly related to the gills of fish, and represent a critical innovation in evolution not shared with animals like flies or earthworms.

In addition to sequencing the two acorn worms in this latest study, the researchers also identified ancient gene families that were already present in the deuterostome ancestor. The researchers compared the genomes of the two acorn worms with the genomes of 32 diverse animals and found that about 8,600 families of genes are evolutionarily related across all deuterostomes.

"Our analysis of the acorn worm genomes provides a glimpse into our Cambrian ancestors' complexity and supplies support for the ancient link between the pharyngeal development and the filter feeding lifestyle that ultimately contributed to our evolution," said Oleg Simakov, one of the researchers, in a news release.

The findings are published in the journal Nature.

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