Science

Scientists discover why snake embryos twist into spirals

A physical mismatch between the growth of a snake embryo's body and its gut forces the lengthening animal to buckle and coil.

Updated Sep 1, 2026 · 13:21 UTC1 reports

The short version

An international research team has found that snake embryos coil into right-handed spirals because their rapidly lengthening bodies outpace the growth of their guts, which act as a physical tether.
The study, published in Current Biology, analyzed over 900 embryos across 39 species using CT scans to observe their internal anatomy.
The findings suggest the early coiling is entirely driven by physical forces and anatomy, though embryos can later shift directions once their muscles mature and the yolk shrinks.

An international research team led by scientists at the Canadian Museum of Nature studied more than 900 snake and limbless squamate embryos across 39 species.[ScienceDaily]
The study, published in Current Biology, found that snake embryos initially curl into a right-handed spiral early in development because their bodies grow faster than their guts.[ScienceDaily]
CT scans of the embryos revealed a detached gut structure surrounded by yolk blood vessels that acts as a physical tether, causing the lengthening body to buckle and coil.[ScienceDaily]
The early coiling direction is determined by physical forces rather than muscular activity, as the embryos lack muscle movement capabilities at that early stage.[ScienceDaily]
As the embryos mature, the yolk shrinks and their muscles develop, allowing about half of the near-hatching embryos to shift or recoil to the left side.[ScienceDaily]