A new study suggests that more animals changed their behavior when non-avian dinosaurs no longer walked on the face of the Earth.
Mammals Evolved After Dinosaurs Disappeared
In the study conducted by University College London and Steinhardt Museum of Natural History of Tel Aviv University, it was noted that the extinction of non-avian dinosaurs 66 million years ago resulted to an explosion in the number of mammals several thousand years after.
Fossil records show that the types and number of mammals ballooned in the absence of dinosaurs. Researchers found out that this growth was due to more animals coming out of the dark and exploring their surroundings during daytime — a behavior that provides a glimpse on mammalian evolution.
Researchers used information gathered from 2,415 mammalian species that still exist today. By applying computer algorithms, they retraced steps of the animals' ancient ancestors and recreated the most probable behavioral patterns.
By analyzing family trees from two different mammals from varying time lines, study proponents deducted that mammals literally let go of their nocturnal existence and switched to more daytime activity as dinosaurs were wiped out. The change was not rapid, however. Over millions of years, the animals went through an intermediate state of mixing daytime and nighttime activity.
While the study is not entirely conclusive, the researchers find the correlation significant.
"It's very difficult to relate behavior changes in mammals that lived so long ago to ecological conditions at the time, so we can't say that the dinosaurs dying out caused mammals to start being active in the daytime. However, we see a clear correlation in our findings," Professor Kate Jones of the UCL Genetics, Evolution and Environment and coauthor said.
Simian Primates Developed Better Visual Acuity And Color Perception
Among all other mammals, the ancestors of simian primates such as gibbons, gorillas, and tamarins were among the first to come out of the dark. This strongly correlates with the knowledge that these simian primates are the ones with comparable visual acuity and color perception with diurnal birds and reptiles.
The researchers believe that populating the mammalian family tree will provide a better picture of this behavioral evolution and that the study could greatly strengthen its claim by conducting another research including an actual observation of a living mammal.
Professor Tamar Dayan, coauthor and chair of The Steinhardt Museum of Natural History of Tel Aviv University, says that fossil evidence alone cannot give a concrete information whether a particular animal exists nocturnally or not. Dayan reiterates that evidences of eventual evolution on daylight existence lie in soft tissues.
The study is published in Nature Ecology & Evolution on Nov. 6.
