The first vertebrates to crawl out of the water onto land about 380 million years ago had extremely stiff necks and could barely turn their heads, according to an international team of paleontologists and biologists from Pennsylvania State University, Uppsala University and Canadian research centers whose study was published in the journal Nature, infohub.kz reports.
The work overturns a long-standing scientific hypothesis that the neck evolved in ancient creatures specifically to let them scan their surroundings and hunt for prey, ScienceDaily writes.
For a long time it was believed that separating the skull from the shoulder girdle, as in the fossil fish Tiktaalik roseae found in Arctic Canada, allowed early tetrapods to look around without turning their whole bodies. However, the spine of these organisms consisted mostly of soft tissue and a notochord, which are poorly preserved in fossils.
To reconstruct the biomechanics of the ancient species, the authors measured the stiffness of the notochord in modern sturgeons, which retain an archaic skeleton, and built computer models of the fossil animals.
The modeling showed that even with the head anatomically separated from the shoulders, the structure of the spine, muscles and skin severely limited movement, preventing the first tetrapods from either nodding their heads or raising them higher than ordinary fish do.
According to study co-authors Tom Stewart and Dana Korneisel, the neck originally arose as a byproduct of skeletal restructuring needed for support and movement on the forelimbs. Neck flexibility took shape much later, once the basic anatomical framework had already become fixed in the course of evolution.