Comb jellies, not sponges, maybe the first ancestors of all animals, groundbreaking study reveals
11:14 AM EST, January 13, 2024
The first unicellular organisms drifted into the sea. Then, approximately 700 to 800 million years ago, clusters of cells came together, forming the first multicellular animal on Earth, suggests the scientific portal "Science". But what was this first animal?
For over a century, biologists have wondered which animal first appeared in the ancient oceans more than half a billion years ago. They sought answers among the most primitive species, and everything seemed to point to sponges for years. However, recently, researchers stumbled upon a new lead.
Could these have been the earliest animals in history?
Scientists employed an innovative approach based on studying chromosome structure. They uncovered compelling evidence that comb jellies, not sponges as previously believed, are likely the "sisters of all living animals."
The results of this groundbreaking study were published in the magazine "Nature" this week. The research team, led by Darrin Schultz from the University of Vienna, examined the gene patterns on the chromosomes of sponges and comb jellies, which led to surprising conclusions.
Scientists identified 14 gene groups on separate chromosomes in comb jellies. In sponges, the same genes were found to be "merged and mixed" across seven groups, reflecting the pattern observed in all other animals.
This implies that the ancestor of comb jellies was likely the first to diverge from the common ancestor of all living animals. All other animals, including sponges, evolved later, after the fusion of these chromosomes.
"If this is true, then it's quite remarkable. From a biological viewpoint, it's very surprising" – Max Telford, a zoologist from the University College London who was not involved in the project, comments for "Nature".
This is surprising because sponges seemed to be the obvious ancestral species to all animals up to now. They are anatomically simple, lacking muscle or nerve cells, attributes that all other animals, including comb jellies, possess. This discovery leads to far-reaching conclusions.
"This suggests that neuron-like cells likely evolved around 100 million years earlier than we originally thought." explains Darrin Schultz, adding that the new study sheds new light on our understanding of evolution.
