CHAPTER XIII 



THE ALLEGED INFLUENCE OF ORDER OF BIRTH 

 AND AGE OF PARENTS UPON OFFSPRING. 



Our information on the subjects treated in the present chapter 

 is in a most unsatisfactory state. It is with some hesitation that 

 I have ventured to discuss them at all, but on account of their 

 importance for the general problem of human evolution it was 

 thought that it might be useful to treat them briefly, even though 

 little more was done than to exhibit the imperfections of our 

 knowledge and to point out some of the pitfalls into which the 

 unwary have so frequently fallen. 



In regard to the influence of order of birth upon offspring 

 there is one conclusion which we may feel warranted in drawing 

 with some confidence. The first born children are apt to be 

 lighter in weight and shorter in height than those of later births. 

 Nothing is involved in the establishment of this conclusion 

 beyond the collection and comparison of data on the weight 

 and size of newly born infants and there is no reason to doubt the 

 generality of the conclusion just expressed. Dr. Matthews Dun- 

 can gives the following data on the weights and lengths of infants 

 according to the order of their birth : 



Pearson submits the following table on the weights of 2,000 

 babies, excluding twins and illegitimate births, from the records 

 of the Lambeth Lying-in Hospital : 



Birth Order 



Boys. 

 Girls. 



Mean Weight 



7.40 

 7-15 



297 



