86 SCIENCE PROGRESS 



surface contain the same amount of phosphoric acid. Rich 

 soil has produced highly nutritious food, and conversely rich 

 food produces fertile land. Man's brain was the product of 

 concentrated food — without which children are soon in diffi- 

 culties. 



We have to account for the action of forces which made 

 steadily in the direction of the human hand and foot, the 

 growth of the brain, the non-development of the special senses 

 and the obhteration of instinct. Two manifest conditions of 

 the environment were abundant nitrogenous food and safety. 

 We may further assume that in order to find the food it was 

 an advantage to assume the upright position, and that intelli- 

 gence was of more value in selecting the food than keen powers 

 of smell or great teeth. Pocock has demonstrated the extreme 

 probability that the apes had learned to walk fairly well before 

 they took to the trees a second time. Their object in attempt- 

 ing to perfect the bipedal gait was presumably to set free their 

 hands while searching for food. This food was not berries on 

 small bushes, or otherwise this diet would have left its mark 

 on the teeth and the digestive system. When the common 

 ancestor first came down from the trees he would scamper off 

 on all-fours the same as the monkeys do, and the search for 

 food amongst rocks and under stones seems to have led to 

 the baboon type rather than to the anthropoid. That is, this 

 animal must have always kept one side of its brain alert for 

 possible carnivorous neighbours while it was looking for food. 

 As the apes stand between the baboons and man it is probable 

 that the forces which produced the ape type with its human 

 characteristics continued to act for a longer period on one 

 branch of the common stock and so brought about the evolution 

 of man. In this sense let us assume that the apes left the 

 common ancestral home in succession and began the secondary 

 changes which have made them what they are. 



Life on the Seashore 



Now, the conditions of safety from the carnivora and a 

 perpetual supply of highly nitrogenous food can only be found 

 combined on the seashore. Carnivorous animals track their 

 prey chiefly by scent, and herein Hes the safety of the shore, 

 for the scent vanishes as soon as the sand has been washed 

 by the next wave. Generally speaking, there is a stretch of 

 dry sand between the water and the grass or trees, so that 

 the beach is not frequented by the herbivora. Leopards some- 

 times search the sand between the tide-marks for dead fish, 

 but they do not find much because the birds and crabs are 

 always waiting for anything that may come ashore. Marsupial 



