英国爱丁堡大学Stephen L. Brusatte、Ornella C. Bertrand小组近日取得一项新成果。经过不懈努力，他们发现白垩纪末期大灭绝后胎盘哺乳动物大脑迅速增大。该研究于2022年4月1日发表于国际学术期刊《科学》杂志。

研究人员使用计算机断层扫描对新发现的古新世化石进行了扫描，结果表明，与哺乳动物大脑随着时间推移稳步扩大的惯例相反，在早期胎盘初期哺乳动物会减小它们的相对大脑大小，因为这时体重增加速度更快。在始新世后期，多个谱系通过感觉区域的显著增长独立地获得了高度脑化的大脑。研究认为，随着稀有幸存者填补空缺的生态位，胎盘辐射开始超过体型增加。随着生态位的饱和和竞争加剧，大脑最终变得更大。

据悉，哺乳动物是脑进化程度最高的脊椎动物，和体型相比哺乳动物的大脑最大。胎盘哺乳动物的大脑特别大，新皮层用于感觉整合，但其起源尚不清楚。

附：英文原文

Title: Brawn before brains in placental mammals after the end-Cretaceous extinction

Author: Ornella C. Bertrand, Sarah L. Shelley, Thomas E. Williamson, John R. Wible, Stephen G. B. Chester, John J. Flynn, Luke T. Holbrook, Tyler R. Lyson, Jin Meng, Ian M. Miller, Hans P. Püschel, Thierry Smith, Michelle Spaulding, Z. Jack Tseng, Stephen L. Brusatte

Issue&Volume: 2022-04-01

Abstract: Mammals are the most encephalized vertebrates, with the largest brains relative to body size. Placental mammals have particularly enlarged brains, with expanded neocortices for sensory integration, the origins of which are unclear. We used computed tomography scans of newly discovered Paleocene fossils to show that contrary to the convention that mammal brains have steadily enlarged over time, early placentals initially decreased their relative brain sizes because body mass increased at a faster rate. Later in the Eocene, multiple crown lineages independently acquired highly encephalized brains through marked growth in sensory regions. We argue that the placental radiation initially emphasized increases in body size as extinction survivors filled vacant niches. Brains eventually became larger as ecosystems saturated and competition intensified.

DOI: abl5584

Source: https://www.science.org/doi/10.1126/science.abl5584