Say you accidentally cut the tip of your finger off. Especially if this happened to you as a child, there’s a good chance it would regrow—skin, nail and all. The same is true for other mammals such as monkeys and mice. Unfortunately, however, our regenerative abilities stop there. While some other creatures, most notably salamanders and starfish, can regenerate entire limbs, mammals don’t have this evolutionary superpower.

Part of the reason why our cells only have a limited ability to regenerate may have to do with our genes. But according to new research, two key environmental mechanisms may be at play, too.

Oxygen and hyaluronic acid may play a role in tissue recovery and regeneration, two new studies suggest.

By Jackie Flynn Mogensen edited by Claire Cameron.