LA JOLLA, Calif. — It was the salamanders.
Juan Carlos Izpisua Belmonte had spent years probing the inner workings of embryos, ferreting out the genes that give a body its shape or allow wings to form instead of legs. He’d tracked wafting chemical messengers that, like traffic police, guide streams of dividing cells either left or right. He’d even found a way to tweak animals to grow extra limbs. But one thing he never stopped thinking about was how salamanders could lose parts of their bodies and then regrow perfect replacements. Was it possible, he wondered, that humans might do the same?
