critical transition of modern mammals from premammalian ancestors.” Of much closer relation to modern mammals were the rodent-like multituberculates. Named for the numerous bumps and cusps on their teeth, multituberculates were by far the most successful mammals of the dinosaur age, appearing continuously in the fossil record from around 170 million years ago until their extinction 35 million years ago. Despite this success, early fossils were fragmentary — a gap filled by Luo and his team when they found the earliest-known complete multituberculate skeleton, described in Science. Similar in size and diet to a modern African dormouse, Rugosodon roamed lakeshores around Asia 160 million years ago. Its surprisingly mobile anklebones suggested that it was an agile, fast runner. Luo points to this adaptation as the basis for all versatile locomotor adaptations, ranging from tree climbing to tunnel digging, that allowed later multituberculates to be so successful. Rugosodon’s teeth were ornamented by numerous ridges and wrinkles, indicating a diet of seeds and insects. Interestingly, the later rise of numerous herbivorous multituberculates seems to have originated from this omnivorous ancestral state. “Multituberculates were able to exploit parts of the ecosystem that were not accessible to many other vertebrates. With Rugosodon, we can finally paint a coherent picture of the evolutionary origin of these prolific and ancient mammals,” Luo said. Luo’s most recent discoveries further illuminate what our ancient mammalian relatives looked like and how they lived. They also serve as evidence that many “mammalian” feeding and locomotor adaptations, as well as such features as hair, arose long ago. However, Luo’s work also reminds us that although these adaptations were widespread, they were certainly no guarantee of evolutionary success. “In a sense, the three big modern mammal branches — monotremes, marsupials and placentals — are all accidental survivors among many other lineages that perished in extinction, like Megaconus or Rugosodon,” Luo said. To hear a podcast featuring Zhe-Xi Luo, PhD, visit http://bit.ly/ScienceLifePodcast. uchospitals.edu/midway
B E H AV I O R A L N E U R O S C I E N C E
A matter of trust How do we decide to trust another person?
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ew research by Margaret Wardle, PhD, research associate (assistant professor), in the Department of Psychiatry and Behavioral Neuroscience, showed that a part of the brain called the caudate may help guide decision-making based on reputation. Wardle worked with K. Luan Phan, MD, professor of psychiatry at the University of Illinois at Chicago, who collected data on a group of adults who underwent fMRI scanning while playing a trust game with different partners. The images showed that the caudate — a small area involved in other kinds of decision-making located near the center of the brain — activated strongly when the subject was dealing with unfair or
indifferent partners, but not with partners who “played fair.” “It’s important to be able to understand what goes on in a normal brain when you are deciding to trust someone, or when you are realizing that this is a bad bet,” Wardle said. The findings may help shed light on how these processes go awry in some conditions such as autism or social phobia, which are characterized by difficulties building interpersonal relationships and trust. This could lead to better understanding of how treatments impact these processes by modulating activity in that part of the brain. The study was published in PLOS ONE. Read more at sciencelife.uchospitals. edu.
N S F G R A D U AT E E D U C AT I O N C H A L L E N G E
BSD team thinks outside the TA box A team of graduate students in the Department of Ecology and Evolution and the Committee on Evolutionary Biology took third place in the National Science Foundation Graduate Education Challenge. Team members were Sebastian Heilpern, Courtney Stepien, Benjamin Krinsky, Robert Arthur and Colin Kyle. Their project, “Beyond the Academy: Enhancing STEM Education through External Graduate Assistantships,” developed a graduate assistant program that will create opportunities for graduates to serve society in a variety of nonacademic settings while expanding the range of career choices for STEM graduates. MEDICINE ON THE MIDWAY
FALL 2013
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