126 PROBLEMS OF EVOLUTION 



Many species of birds owe their success in the world to their 

 sociability. Rooks (Gorvus frugilegui) in their crowded rookeries 

 or as they fly in large flocks are able to beat off their enemies. 

 When a party of curlews (Numenius arquata) are feeding, it is 

 almost a certainty that one of the number, by means of some 

 sense or other, will become aware of any danger that is 

 approaching and give warning to the rest. And the sociability 

 that thus protects them we cannot regard as entirely instinctive : 

 it is partly habit learnt in each generation by the young from 

 their elders. And thus it comes about that the tradition of the 

 species to some extent decides the course of its evolution by 

 deciding the manner of life that its members are to lead. Those 

 to whom life in a community proves uncongenial probably fall 

 victims to enemies. 



Does this Can this newly-discovered principle help to heal the feud 

 recondle Detween t ^ ie followers of Weissman (the Neo-Darwinians) and 

 Neo-Dar- the Lamarckians ? If it can, then the Lamarckians must have 

 ith^Lam 1 a sm g u ^ ar power of mistaking an utter rout for a compromise, 

 arckism? For what the new principle shows is not that acquired character- 

 istics can be transmitted, but that Natural Selection can without 

 such transmission do what Lamarckism claimed that it had the 

 exclusive right and power to do. Each generation decides in 

 the main the environment of the next and insists that it shall 

 live in that environment. Those of the young survive who, 

 with the aid of some training, are able to accommodate them- 

 selves to the environment in which they are put. The similarity 

 of environment in each generation leads to selection for similar 

 characteristics : modifications and accommodations in the in- 

 dividual though not transmitted are followed by variations and 

 adaptations in the race, the very phenomenon which has always 

 been the Lamarckian's most formidable weapon. This can now 

 be explained on Neo-Darwinian principles, and if you can show 

 that your opponent's theory is not the only nor the best way of 

 accounting for the facts which he himself adduces, you cut the 

 ground from under him. A simile may perhaps make it clear 

 how the principle works. We may look upon a species as a 

 huge herd of animals that are being driven along a road : the 



