Evolution: origin of sympathetic nervous system (Evolution)

by David Turell , Thursday, May 09, 2024, 15:57 (196 days ago) @ David Turell
edited by David Turell, Thursday, May 09, 2024, 16:02

It runs our organs:

https://www.sciencenews.org/article/lampreys-nervous-system-evolution-cells

"With terrifyingly sharp teeth arranged around a circular mouth, lampreys look about as primitive a vertebrate as you could imagine. But a new study finds that the animals have a surprising similarity to people: Lampreys have the nerve cells responsible for the “fight or flight” response. The finding challenges the idea that this part of the nervous system emerged later in evolutionary history, and it puts lampreys closer to complex vertebrates — like humans.

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"Sea lampreys (Petromyzon marinus) belong to a group of fish called jawless vertebrates, which scientists thought lacked nervous system characteristics seen in jawed vertebrates, such as the sympathetic nervous system. This system is what’s behind the “fight or flight” response, and it activates the body by releasing hormones to control body temperature and cardiovascular function.

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"The team used a technique that tags and lights up specific mRNA in individual cells of lamprey embryos. That allowed the researchers to look at three or four genetic factors associated with sympathetic neurons simultaneously. A cluster of cells lining the heart and the trunk of the embryonic lampreys had these genetic factors, indicating that the cells were the sympathetic neurons seen in other vertebrates, the team reports April 17 in Nature.

"Next, the team tracked where these cells originated by injecting a dye to label cells of the neural crest, a patch of stem cells that migrate during development and give rise to cells of the peripheral nervous system. The lamprey’s sympathetic neurons lit up with the dye, showing that the cells came from the neural crest, just like they do in more complex vertebrates.

"But there were also key differences. Compared with other vertebrates, the lamprey’s sympathetic nervous system formed much later in development and the clusters of cells were smaller. Previous studies may have missed these cells by looking for them at the wrong time during embryo development. So even though the sympathetic system is present, it’s rudimentary nonetheless, Bronner says. “It’s very simplified compared to what it would be in mammals.”

"The findings suggest that the sympathetic nervous system was not an innovation of jawed vertebrates, but rather that the blueprint for it has been around since even before lampreys diverged from the main vertebrate line about half a billion years ago, says Shreyas Suryanarayana, a neuroscientist at Duke University who was not involved with the study. (my bold)

“'As you look deeper, it becomes clear that the basic building blocks of these complex systems present in humans are, in fact, very old,” Suryanarayana says. In more complex vertebrates, this system then diversified, expanded and grew larger, he says.

Comment: note my bold. This article shows that what develops in evolution is not a sudden appearance of a new innovation, but a step based upon much older preparatory developments. Viewing evolution from a purposeful point of view, this makes perfect sense. Bake in steps to the future early on. This is what a designer would do. This answers dhw's complaint that God made 99.9% of unnecessary organisms just to throw them away. They were all part of a purposeful development, step-by-step to a goal, or as in evolution steps to many, many goals.