Possible rewriting: New Study Suggests Comb Jelly Might Be the Oldest Known Animal on Earth

A groundbreaking study published in Nature has revealed that scientists may have identified the first animal to have inhabited Earth 700 million years ago. The study, conducted by researchers at the University of California Berkeley, suggests that the earliest animal was likely a comb jelly, or ctenophore – a predator that traverses the ocean in search of food.

While comb jellies resemble jellyfish, they are distinct creatures that use cilia, rather than tentacles, to propel themselves through water. These unique animals are still present in marine ecosystems today and can be found in waters across the globe.

Daniel Rokhsar, a co-author of the study and a professor at UC Berkeley, stated, “The most recent common ancestor of all animals probably lived 600 or 700 million years ago. It’s hard to know what they were like because they were soft-bodied animals and didn’t leave a direct fossil record. But we can use comparisons across living animals to learn about our common ancestors.”

For a long time, there has been a debate regarding which animal came first – the ctenophore or the sponge. Sponges are stationary creatures that filter water through their pores to collect food particles. Many have argued that due to the sponge’s primitive features, it came before the ctenophore. However, this new research has determined that while sponges did appear early, they were likely second to ctenophores.

Scientists made this determination by analyzing the organization of genes in the organisms’ chromosomes. The chromosomes of ctenophores differ significantly from those of sponges, jellyfish, and other invertebrates. This difference led researchers to suspect that ctenophores either appeared much earlier or much later than the other animals.

Rokhsar explained, “At first, we couldn’t tell if ctenophore chromosomes were different from those of other animals simply because they’d just changed a lot over hundreds of millions of years. Alternatively, they could be different because they branched off first, before all other animal lineages appeared. We needed to figure it out.”

The “smoking gun” for researchers was when they compared the chromosomes of ctenophores to non-animals. It was discovered that ctenophores and non-animals shared specific gene-chromosome combinations, while the chromosomes of sponges and other animals were rearranged in a distinct manner.

This new insight is invaluable for understanding the fundamental functions of all animals, including humans, such as eating, moving, and perceiving our environment.