Did Humans Originate from Ancient Jawless Blood-Sucking Fish? Here’s What the New Study Says

Sea lampreys, known for their blood-sucking habits, are now helping scientists uncover secrets of early vertebrate evolution [Image: Canva]

In an astonishing breakthrough, scientists have discovered that jawless, bloodsucking fish like lampreys could hold the key to understanding the evolution of humans and other vertebrates. A study published on July 26 in the journal *Nature Ecology and Evolution* reveals that these ancient creatures, notorious for their terrifying appearance and lack of jaws, possess a crucial cell population that was vital to the origins of vertebrates.

The ancestors of modern vertebrates, including humans, date back to ancient fish that thrived over 400 million years ago in the Devonian era. At that time, jawless fish dominated the seas, while jawed vertebrates were rare. Today, the situation is reversed. Lampreys and hagfish are the only surviving groups of these once-dominant jawless vertebrates, making them invaluable for studying early vertebrate evolution.

According to Carole LaBonne, a professor of molecular biosciences at Northwestern University and lead researcher, "Lampreys could be the missing link to unlocking the secrets of our evolutionary past." She explains that to understand the origins of a particular trait, scientists must look to simpler, more primitive species like lampreys, rather than more complex vertebrates that have undergone millions of years of independent evolution. You need to look backwards to whatever the most primitive version of the type of animal you're studying is, which leads us back to hagfish and lampreys — the last living examples of jawless vertebrates."

The research team compared the genes of lampreys with those of Xenopus, a group of jawed, aquatic frogs. They focused on genes regulating a stem cell population known as the neural crest, which is unique to vertebrates and played a pivotal role in vertebrate evolution. These stem cells contribute to diverse cell types, tissues, and structures essential for vertebrate development.

The researchers discovered a similar gene network in both lampreys and Xenopus, with one significant difference: a stem cell-regulating gene called pou5 was not expressed in the neural crest cells of lampreys. This absence may explain why lampreys lack jaws and other skeletal features found in jawed vertebrates. The study also examined pluripotent blastula cells, primitive cells capable of becoming any other cell type in the body. The presence of an intact pluripotency network in both lampreys and Xenopus suggests that these cells evolved early in the vertebrate lineage.

Joshua York, lead author and researcher at Northwestern University, notes that "the fact that pou5 can trigger neural crest development in frogs, despite being inactive in lampreys, suggests that this gene played a crucial role in a primitive cellular network that existed in the common ancestors of vertebrates, highlighting its significance in the evolutionary history of neural crest formation."

The findings suggest that pou5 was present in the ancestor of both jawed and jawless vertebrates and was later lost from the neural crest of jawless vertebrates. This discovery challenges our understanding of how complex features evolve, indicating that innovation in nature often comes from repurposing existing genetic programs rather than inventing entirely new ones.

The implications of this research extend beyond evolutionary biology. Neural crest cells play crucial roles in human embryonic development, and abnormalities in their development can lead to various congenital disorders. By understanding the ancient origins and regulation of these cells, scientists may gain new insights into these conditions and potential therapeutic approaches.

This study also underscores the importance of preserving and studying diverse species, even those considered pests. While lampreys are often viewed as nuisances in Great Lakes fisheries, they provide a treasure trove of evolutionary information. This research highlights the common evolutionary heritage written in our genes, from jawless lampreys to humans with complex brains and versatile hands.