THE LINEAGE OF MAN 



To return to the fossil mammals: Our knowledge of the 

 very long period after the mammals first appeared, during 

 the ages when the dinosaurs and other reptiles dominated 

 the scene, is extremely meagre. From a study of recent 

 mammals Huxley predicted that the remote common ances- 

 tors of all the highly diversified placental mammals would 

 be found to be small insectivorous forms, not unlike some 

 of the recent insectivores, such as the Madagascar tenrec 

 (^Centetes) in general appearance and habits. From a study 

 of the teeth of later mammals Professor Henry Fairfield 

 Osborn likewise predicted that the ancestral placentals, liv- 

 ing perhaps in the Lower Cretaceous period, would have 

 teeth of the generalized insectivorous type. Quite recently 

 Dr. Roy C. Andrews and his colleagues have contributed 

 important evidence in favor of this view by discovering in 

 a Lower Cretaceous formation in the Gobi desert in Mon- 

 golia the fossil skulls of several kinds of small mammals. 

 Some of these combine features of the later insectivores and 

 primitive carnivores and thus appear to afford a generalized 

 pattern for the divergent evolution of the insectivores, carni- 

 vores, herbivores, tree-shrews, and primates, all of which are 

 first definitely known to have lived in Palaeocene time in 

 North America, at the beginning of the Tertiary period, or 

 so-called Age of Mammals. 



Palaeontologists are confident that these already diversified 

 mammals were not suddenly created in Palaeocene time, 

 holding that they were derived by evolutionary changes from 

 the more primitive mammals of the Cretaceous and Jurassic 

 periods, from some of which they inherited certain striking 

 characters of their dentition. 



Once we have passed out of the obscurity of the very long 

 period during which the reptilian hosts dominate the fossil 

 record and the mammals remain far too inconspicuous, we 



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