A rapidly evolving sequence from the human genome drives gene activity in the developing thumb, wrist and ankle of mouse embryos, suggesting the sequence may have contributed to key evolutionary changes in the human limbs that allowed us to walk upright and use tools.

An indication of their biological importance, many of these non-coding sequences have remained similar, or “conserved,” even across distantly related vertebrate species such as chickens and humans. Recent functional studies suggest some of these “conserved non-coding sequences” control the genes that direct human development.