Studies have found that the ancestors of giant pandas may not be ＂vegetarian＂： there used to be many kinds of diets.

　　Reference message networkReported on February 5Foreign media said that the study found that compared with modern giant pandas, the ancestors of giant pandas had a wider diet, not just eating bamboo.

　　According to the British "Economist" website reported on January 31, the giant panda is the darling of environmentalists. It is the mascot of WWF and one of the most recognizable large animals in the world. In evolution, it is also very strange. It is a bear. According to their usual eating habits, it should be a carnivore, but it is a herbivore. This is very rare.

　　Wei Fuwen, an academician of the China Academy of Sciences and a researcher at the Institute of Zoology of the Chinese Academy of Sciences, published a paper in Contemporary Biology, saying that compared with modern giant pandas, the ancestors of giant pandas had a wider diet.

　　Giant pandas are not only herbivores, but also only eat a single kind of food — — Bamboo. Wei Fuwen wants to know when the change to eating only one kind of food took place. The answer is that it is closer than anyone expected.

　　According to the report, in the past, the speculation about the diet changes of giant pandas relied on the study of their skulls and genes. The mandible fossils of 4 million years ago show that the ancestors of modern giant pandas had eaten a lot of hard plants by then. Analysis of a gene named Tas1r1 shows a similar situation. This shows that the selection pressure in favor of this gene began to ease about 4.2 million years ago. According to the traditional theory, about two million years ago, the giant panda had completed the transition to the eating habit of eating only bamboo. However, Wei Fuwen provided a third piece of evidence. This is the isotopic composition of the giant panda’s bones and teeth.

　　The most common elements in food are carbon, oxygen and nitrogen. Each element has several isotopes. The two main isotopes of carbon are 12C and 13C, and the two main isotopes of nitrogen are 14N and 15N. These isotopes have different proportions in different plant species — — These proportions are often preserved in the tissues of animals that eat these plants. Oxygen isotopes 16O and 18O have different proportions according to the local climate.

　　According to the report, Wei Fuwen studied the carbon and nitrogen isotopes in the bones of 12 giant panda ancestors, which can be traced back to 11,000 to 5,000 years ago, and compared them with the carbon and nitrogen isotopes of modern giant pandas. Compared with modern giant pandas, the proportions of 15N/14N and 13C/12C in the ancestors’ bones of giant pandas are larger, which indicates that they have a wider diet. Oxygen isotopes collected from tooth fossils show a similar situation. These giant panda ancestors had more 18O/16O variables, which indicated that they lived in more diverse environments than modern giant pandas.

　　It is not clear whether these giant panda fossils studied by Wei Fuwen were still carnivorous at that time. However, it is clear that they did not eat only bamboo as they do now. They lived on the edge of forests, subtropical areas and open land, not just in bamboo forests. (Compile/Yin Xia)