Nightmare fish may explain how our 'fight or flight' response evolved

Lampreys are the stuff of nightmares, complete with long, slimy bodies; circular mouths filled with teeth; and parasitic tendencies. But lampreys are also vertebrates, which means they have bacKBOnes and share a common ancestor with humans — and new research is revealing that we have more in common with these slippery bloodsuckers than scientists previously thought.

Lampreys belong to an ancient vertebrate lineage known as Agnatha, or jawless fish. Previous research suggests that lampreys and their relatives represent the most primitive group of vertebrates still in existence, having evolved an estimated 360 million years ago. These living fossils can give us a window into how some of our distant ancestors likely evolved.

For the last 150 years, scientists assumed that lampreys lacked a jaw because they were missing a structure known as the neural crest. This group of stem cells is unique to vertebrates, and in the womb or the egg, it develops into a wide array of structures. These structures include both jaws and the sympathetic nervous system, which controls our involuntary fight-or-flight response that kicks on in dangerous or stressful situations.

But a new study, published Wednesday (April 17) in the journal Nature, reveals that lampreys have sympathetic nerve cells after all — suggesting that the vertebrate flight-or-flight response is more ancient than scientists expected.

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"Studies like this help teach us how we were built over evolutionary time," Jeramiah Smith, a computational biologist at the University of Kentucky who was not involved in the research, told Live Science.

The new study did not begin as a search for sympathetic nerve cells.