[33]Bird brains and traffic accidents

感谢收听,期待你对本期节目的评论留言哦～ 2017.4.01 Economist Science and Technology Bird brains and traffic accidents Small is not beautiful A new evolutionary[ˌi:vəˈlu:ʃənri]进化的pressure maybe at work in the avian [ˈeɪviən]鸟类的 world. Natural selection is a harsh interrogator [ɪn'terəɡeɪtə(r)]质询者 at the best of times. But if you are a bird, it has an extra question, not asked so forcefully of animals that cannot fly: “is that extra gram of weight really necessary?”Contrary to the insult “birdbrained”, birds are not notably显著地 more stupid than mammals, but the pressure to keep organs light applies to the cerebrum[səˈri:brəm]大脑 as much as it does to anything else. For the past century, though, birds have faced a new enemy that might require them to get smarter: the motor car. These days, cars and other motorised vehicles kill around 250m birds a year. That sounds like a significant selective pressure, so Anders Moller, an evolutionary biologist at the University of Paris-Sud, in France, decided to find out whether it really was. Dr Moller’s hypothesis[haɪˈpɒθəsɪs]假设，前提 was that avoiding vehicles needs intelligence, and intelligence needs a big brain. The conclusion of this syllogism [ˈsɪlədʒɪzəm]演绎推理 is that small-brained birds are more likely to be road-kill than largebrained birds are. To test this idea, though,he needed data on a lot of dead birds. That serendipity[ˌserənˈdɪpəti]机缘巧合 plays a part in science is undeniable. Fleming’s chance observation of Penicillium[ˌpenɪ'sɪlɪəm]青霉菌 mould on bacterial plates led to antibiotics抗生素. Kekulé’s dream of carbon atoms dancing in rings led to his model of the structure of benzene[ˈbenzi:n] 苯. Dr Moller’s serendipity was to meet, 30 years ago, a taxidermist（动物标本）剥制师[ˈtæksɪdɜ:mɪst] called Johannes Erritzoe. Mr Erritzoe has, during his career, exhaustively用尽一切地 recorded details of the specimens样品[ˈspesɪmən] that have passed through his hands. These details include the weights of the internal organs, and likely cause of death, of 3,521 bird specimens of 251 species. Since they met, Dr Moller and Mr Erritzoe have collaborated on many papers. This time, they asked whether there was a difference between the weights of the organs of birds killed by traffic and of those that had died of other causes. They found, as they report in Royal Society Open Science, that there was not—with a single exception. The smaller a bird’s brain, when controlled for its body size, the more likely it was to have been road-kill. Some 60% of the smallest-brained birds Mr Erritzoe handled had died this way. Among the largest-brained, death by traffic was unheard of. All this suggests a selective pressure on birds in parts of the world with lots of traffic to acquire bigger brains, even at the cost of the extra energy required to keep those brains airborne. It also leads to a prediction, in a field of science—evolutionary biology—that is rarely in a position to make them. This is that the average weight of bird brains may rise over coming decades. Whether anyone with Mr Erritzoe’s enthusiasm for data collection will provide the means to test that prediction is, though, a different question. 1.The clouds in Camarillo----Brazzaville