EVOLUTION AND MANKIND. 293 



trial creatures with limbs lifting the body off the ground. They 

 were somewhat lizard-like on the one hand and mammal-like on 

 the other. The teeth in some were differentiated into incisors, 

 canines and molars. Pariasanrns, from the Karroo formation, 

 attained a length of ten or eleven feet. 



The origin of birds from reptilian ancestors has been con- 

 clusively demonstrated on anatomical and embryological grounds. 

 They developed a special dermal cm^ering of feathers. The 

 skeleton of the earliest-known bird, Archaeoptcryx , was found 

 in the lithographic slates at Solenhofen in Bavaria, belonging to 

 the Upper Jurassic age. Archaeopteryx was about the size of 

 a rook, and had teeth, which are absent in the modern bird. The 

 digits of its anterior limb or wing are not so much reduced as in 

 modern birds. 



Mammals appeared at an earlier date than birds. Their 

 remains have been found as low down as the Trias, but the group 

 (lid not attain much importance before the Tertiary epoch, when 

 it replaced the reptiles as the dominant group of vertebrates. 

 Mammals probably arose from some primitive group of reptiles 

 such as the Theromorphs, which themselves show affinities with 

 extinct Labyrinthodont Amphibia. 



As an example of the completeness of the geological record in 

 some cases, brief reference may be made to the ancestry of the 

 horse. The Equidae are generally considered to have originated 

 from a primitive five-toed Ungulate, appearing in early Eocene 

 times. Passing through the Eocene to the Oligocene and Miocene 

 epochs are a series of horses which gradually increased fri >ni 1 1 

 inches in height in the Eocene to 48 inches at the end of the 

 Miocene. The modern horse is about 64 inches high. Contem- 

 poraneously there was a continual reduction in the numljer of 

 toes, the Eocene horse having four toes in front and three behind, 

 the Miocene horses being three-toed, while the modern one- toed 

 horse — ^with its splint bones- — made its appearance at the same 

 time as three-toed horses were disappearing in the Pliocene. 

 With increase of stature came increase of swiftness, their necks 

 became longer, their teeth more complex, and their brains larger. 

 Thus has evolved the modern horse, running on tiptoe on Mie 

 middle digit of its original pentadactyl limb. 



The elephants probably originated from the same primitive 

 Ungulate group as the horses. Correlated with the development 

 of special characters came increase in size. In the skull the occi- 

 pital or back region gradually began to grow upwards, the nasal 

 opening in the skull passed ftirther back, the second incisor teeth 

 fonnecl tusks, but ultimately only those of the upper jaw re- 

 mained. The chin at first lengthened, but afterwards shortened, 

 in order to allow greater flexibilit}- to the proboscis. 



It may be asked, why did so many of the animals just tnen- 

 tioned die out? Probably their extinction was due to their lack 

 of power of adaptation to their environment, to which their huge 

 size often contributed. This increase in size may. perhaps, be 

 correlated with disturbance in the development and function of 



