414 ANNUAL REPORT SMITHSONIAN INSTITUTION, 193 3 



All this naturally stimulates the inquiry into the causes of these 

 phenomena. And the first direction of the inquiry turns to the 

 skull. Is not a low or high forehead conditioned by low or high 

 frontal part of the skull ? Observation shows that exceptionally low 

 or high front is to some extent attended by low or high forehead 

 in the living; but if such extremes are eliminated it soon becomes 

 manifest that there is but little correlation between the two. What 

 differs is not so much the height of the bony front as the extension 

 downward of the hairline. The variation in the height of the fore- 

 head in the living is essentially a variation in the height of the 

 hairline, regardless largely of the underlying slmll. 



What causes the variation in the normal hairline can only be de- 

 termined by further research. It is certain that low or again high 

 foreheads " run in families." And it is plausible to accept that under 

 the influences of segregation, isolation, and perhaps some form of 

 conscious or unconscious selection, lower or again higher foreheads 

 may become generalized in a locality or in a racial group. The case 

 of the Indians suggests that an important part may have been 

 played by sexual selection. 



In addition, some causes of different lowness or height of hair 

 insertion over the forehead may possibly lie in the hair system itself, 

 with its blood supply and innervation; but it would be difficult to 

 state precisely any definite factors in this connection. 



