

Four 



• • • • • • ■ • 



Uncles and aunts 



Cousins 





grandparents VZX o ? 





Father 



Mother 



Brothers 



Sister 



Uncles and aunts 



Ernest 



Cousins 



WHAT RUNS IN FAMILIES? 



Ernest has blue eyes, although both his parents and his sister and his brothers have 

 dark eyes — like his cousins and his uncles and his aunts. Some say he gets his blue 

 eyes from his grandmother Brown, but others say he gets them from his grandfather 

 Green. How can we tell? 



improve the stock by breeding from the swiftest. And the modern race 

 horse is indeed a great improvement upon the progenitor of only a few decades 

 back. Do- the training and racing of horses influence the performance of 

 their offspring? Or does the performance reveal the possibilities of the 

 stock? Or how is the stock improved? 



What people have believed about the connection between parent qualities 

 and offspring qualities has influenced their treatment of pregnant mothers. 

 There has been a widespread belief, for example, that if a pregnant female 

 experienced a violent shock or a violent pleasurable emotion, the unborn child 

 would somehow show the effects. Birthmarks, deformities, and even special 

 talents were often ascribed to such experience. Many animal-breeders tried 

 to influence the coloring or markings of their calves or lambs by exposing the 

 mothers to appropriate scenery. Similarly, many human mothers today hope 

 to ensure beautiful features for their unborn babies by gazing on the pictures 

 of beautiful women or men. 



People generally think of "heredity" as a strange, mysterious force, which 

 may or may not strike, like lightning or good luck or a pestilence. It is only 

 in modern times that systematic research has attempted to solve the larger 

 problems of heredity. For example, how can we measure degrees of resem- 

 blance among individuals? Houj far can selection be carried? Can a stable, 



473 



