io8 The Descent of Man. Pabt I. 



continue to exist, and thus unintentionally to commit suicide. 

 Every one knows how strong the maternal instinct is, leading 

 even timid birds to face great danger, though with hesitation, 

 and in opposition to the instinct of self-preservation. Neverthe- 

 less, the migratory instinct is so powerful, that late in the autumn 

 swallows, house-martins, and swifts frequently desert their 

 tender young, leaving them to perish miserably in their nests.'^' 



AYe can perceive that an instinctive impulse, if it be in any 

 way more beneficial to a species than some other or opposed 

 instinct, would be rendered the more potent of the two through 

 natural selection ; for the individuals which had it most strongly 

 developed would survive in larger numbers. Whether this is the 

 case with the migratory in comparison with the maternal instinct, 

 mp.y be doubted. The great persistence, or steady action of the 

 former at certain seasons of the year during the whole day, may 

 give it for a time paramount foi'ce. 



Man a social nuimal. — Every one will admit that man is a 

 social being. We see this in his dislike of solitude, and in his 

 wish for society beyond that of his own family. Solitary con- 

 tinement is one of the severest punishments which can be 

 inflicted. Some authors suppose that man primevally lived in 

 single families ; but at the present day, though single families, 

 or only two or three together, roam the solitudes of some savage 

 lands, they always, as far as I can discover, hold friendly 

 relations with other families inhabiting the same district. Such 

 families occasionally meet in council, and unite for their common 

 defence. It is no argument against savage man being a social 

 animal, that the tribes inhabiting adjacent districts are almost 

 always at war with each other ; for the social instincts never 

 extend to all the individuals of the same species. Judging from 

 tlie analogy of the majority of the Quadrumana, it is probable 

 that the early ape-like progenitors of man were likewise social ; 

 but this is not of much importance for us. Although man, as 



" This fact, the Rev. L. Jenyns hatched. Many birds, not yet old 



states (see his edition of 'White's enough for » prolonged flight, ai-e 



Nai. Hist, of Selborne,' 1853, p. likewise deserted and left behind. 



204) was first recorded by the illus- See Blackwall, 'Researches in Zoo- 



trious Jenner, in 'Phil. Transact.' logy,' 1834, pp. 108, 118. For some 



1824, and has since been confirmed additional evidence, although this 



^y several observers, especially by is not wanted, see Leroy, ' Lettres 



Mr. Blackwall. This latter careful Phil.' 1802, p. 217. For Swifts, 



observer examined, late in the Gould's 'Introduction to the Birds 



lutnmn, during two years, thirty- of Great Britain,' 1823, p. 5. Simi- 



six nests ; he found that twelve lar cases have been observed in 



contained voung dead birds, five Canada by Mr. Adams ; ' Pop. 



contained eggs on the point of being Science Review,' July 1873, p 



hatched, and three, eggs not nearly 283. 



