How Much of a Role Does Limber Regeneration Play?

Limb regeneration or the ability to grow back pairs of legs is not unheard of in the animal kingdom. The champions of regeneration though turn out to be sea spiders. They can also rebuild their digestive tract and even their reproductive organs some even survive off to being cut literally in half. So what could be behind this amazing regenerative biology and why don't we see such a useful adaptation more often in biology for instance among us humans will tingle spoke to University of Vienna's Gerg Brinise.