Gustavo Barja is Professor in the Department of Animal Physiology-II at Complutense University of Madrid, Spain. The researcher at the Faculty of Biological Sciences of the Complutense University of Madrid, addresses the relationship between aging and the production of compound molecules known as reactive oxygen species (ROS). Reactive oxygen species include free radicals, molecules that Barja has been studying for a long time. Specifically, his work has focused on finding out the relationship between free radicals and the longevity of animals, both in those that live long as pigeons and cows and in others that have a shorter life cycle. "As a result of these experiments, it has been observed that long-lived animals, rather than having a lot of antioxidants (ROS neutralizing substance), as previously believed, have little production of radicals in their mitochondria - a part of the cell where cellular respiration occurs ", explains Barja. Barja tends to emphasize studies that indicate that antioxidants do not control the speed of aging, which conclude that this factor is determined by the production of radicals rather than their elimination (action carried out by antioxidants).