How to Get A Head in Life: Scientists Unveil When Humans’ Ancestors Developed Noggins
23:28 GMT 20.05.2022 (Updated: 13:32 GMT 06.08.2022)
© Sputnik / Alexey Filippov
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Scientists in Australia discovered in 2018 the existence of a string of brain cells existing in the human colon, which they called a “second brain” operating independently of the rest of the central nervous system to push waste out. However, it’s likely it evolved first, they said, before the actual brain.
A research team led by the University of Oxford has revealed how vertebrates developed heads. Their study was published on Wednesday in Nature.
It might seem like common sense to us since we have heads, but animals didn’t always have them, we had to evolve them, and that process took an immensely long time. The scientists’ study looked at just how that process happened in vertebrates, including developing a superior head to that of invertebrates, which allowed their evolution to take off.
According to Science Alert, heads give us a lot of advantages, including a place where concentrated sensory nerve nodes can be located, which in their very first stages were clusters of cells called Cranial Sensory Ganglia; today we call them ears, nose, and eyes. To study how vertebrates went from having no definitive head to having one, the scientists looked at vertebrates' closest invertebrate relative: tunicates, also known as sea squirts.
"Tunicates are like an evolutionary prototype for vertebrates," explained Ute Rothbächer of the University of Innsbruck’s Institute of Zoology in a news release.
"There is a large anatomical gap between the adults of these subphyla, as they are adapted to ecological niches. This complicates research on their evolution. Common structures and mechanisms can only be identified at the embryonic stage,” he explained, adding that “our common ancestor was probably very similar to a tunicate larva."
As a comparison, they looked at the DNA of a lamprey, a boneless fish that hasn’t changed much in 360 million years - only about 200 million years after vertebrates first developed something of an eye.
Using the gene technology CRISPR-Cas9, the researchers isolated the gene that develops Bipolar Tail Neurons in tunicates, called “Hmx,” finding that it’s almost the same gene that causes Cranial Sensory Ganglia to form in vertebrates.
"Hmx has been shown to be a central gene that has been conserved across evolution," University of Innsbruck zoologist Alessandro Pennati said in the release. "It has retained its original function and structure and was probably found in this form in the common ancestor of vertebrates and tunicates."
In other words, the gene that tells lampreys to grow heads is the same gene that tells sea squirts to grow tails.
