Resumen de Letters.

Soeren Hansen, Jon D. Sobotka, Martin J. Greenwood, Deepak Chopra, Sandor Frecska

• Several letters to the editor are presented in response to articles in the September 2016 issue, including "A History in Layers,” by Jan Zalasiewicz, "Where Will All the New Neuroscientists Go?,” by Gary Stix and "At the Boundary of Knowledge,” by Michael Shermer.