Robots are going to do many things for us in the future. It makes sense for them to be mechanically robust to impacts while working in an unknown environment. As this video from DLRRMC shows, developing a flexible spine for humanoid robots is one way to approach this problem.
As the developers explain:
Compared to the human spine stabilized by ligaments, intervertebral discs and muscles, we use a continuum mechanism based on silicone and tendons for actuation… a modular multiple DOF prototype is built which can easily be equipped with different tendon routing and elastic continuum shapes.
More information is available here.