Snake Evolution: Did We Have it Backwards?
Snakes may not have evolved in the way that researchers have long thought. That is, where snakes evolved to become more simple over time, losing the limbs that their reptilian ancestors may have boasted. Now, a new study suggests just the opposite, finding evidence that snake vertebrate is not all that "simplified" after all.
That's at least according to a study recently published in the journal Nature, which details how paleobiologists Jason Head of the University of Nebraska-Lincoln, and P. David Polly of Indiana University Bloomington found distinctions among snakes' vertebral bones that matched those found in the backbones of four-legged lizards.
These results indicate that snakes still boast genes which govern the distinctions between the neck, trunk, lumbar, sacral, and tail regions of limbed animals - called Hox genes.
It was long through that snakes evolved from limbed semi-aquatic ancestors after the expression of these genes was disrupted in snakes, leading to a simplification of their bodies and the development of their remarkably efficient side-winding form of locomotion.
But when Head and Polly took a closer look at the vertebral columns of snakes, they found that snakes boast an unexplained level of complexity.
"If the evolution of the snake body was driven by simplification or loss of Hox genes, we would expect to see fewer regional differences in the shapes of vertebrae," Head explained in a statement. "Instead, what we found was the exact opposite. Snakes have the same number of regions and in the same places in the vertebral column as limbed lizards."
More amazing still, when the researchers compared the genetic regions in snakes and lizards thought to be associated with Hox gene expression, they found that the information matched.
"Our findings turn the sequence of evolutionary events on its head," Polly added, suggesting a new theory. "It isn't that snakes have lost regions and Hox expression; it is that mammals and birds have independently gained distinct regions by augmenting the ordinary Hox expression shared by early amniotes."
However, if the researcher pair is right, new theories concerning genital development among reptiles will also have to be called into question. You can read more about that controversial theory here.
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