For many years, scientists have looked for the earliest split on the animal tree of life. This event happened about 600 million years ago, marking the split of all living animals—from mammals to mollusks—from a common ancestor. A major debate has been about which lineage branched off first: sea sponges or comb jellies.
Sea sponges and comb jellies are simple aquatic creatures. They were thought to hold clues about early animal life. However, it was tricky to determine their exact positions on the evolutionary tree because their genomes have changed over time.
Recently, researchers introduced a new method. Instead of just comparing the types of genes organisms have, they looked at where those genes sit on chromosomes. According to Popular Mechanics, as species evolve, their genes shift around. Once they move, they usually stay in their new spots, providing a clearer picture of their evolutionary history.
In this study, scientists analyzed 14 gene groups in both sponges and comb jellies, comparing them to closely related, single-celled organisms. They found that comb jellies and their one-celled relatives had these gene groups on separate chromosomes, suggesting limited rearrangement. In contrast, sponges had these 14 gene groups clustered into just seven. This indicates that sponges split from the common ancestor after the comb jellies did—showing more genetic changes.
This research determined that comb jellies were the first to branch off. They now stand out as the most genetically distinct animals today. This finding not only settles a long-standing debate but opens new doors for understanding how complex life evolved. The study positions comb jellies as a “sister” lineage to all other animals, meaning their evolutionary path diverged early and independently.
This distinction could influence how scientists study the development of complex features, like nervous systems and digestive tracts, in other animals. It also emphasizes that unique traits in comb jellies may actually be evolutionary advancements, rather than mere primitive characteristics.
The implications of confirming the comb jelly’s position go beyond just categorizing animals. It gives researchers a clearer lens to examine the evolution of the entire animal kingdom. By focusing on gene location instead of just content, progress can be made in understanding evolutionary mechanisms not only for animals but also for other life forms.
This innovative approach may help scientists tackle other unresolved questions in biology, making it a significant development in the field.
