j6o POPULAR SCIENCE MONTHLY. 



we are warranted in dismissing them from further consideration 

 in this place. 



Anthropologists have endeavored for a long time to find the 

 cause of these differences in the color of the skin.* Some have 

 asserted that they were the direct effects of heat ; but our map 

 shows that the American stock, for example, is in no wise affected 

 by it. A consideration of all the races of the earth in general 

 shows no correspondence whatever of the color of the skin with 

 the isothermal lines. The Chinese are the same color at Singa- 

 pore as at Pekin and at Kamchatka. Failing in this explanation, 

 scientists have endeavored to connect pigmentation of the skin 

 with humidity, or with heat and humidity combined ; but in 

 Africa, as we saw, the only really black negroes are in the dry 

 region near the Sahara Desert, while the Congo basin, one of the 

 most humid regions on the globe, is distinctly lighter in tint. 

 Others have attempted to prove that this color, again, might be 

 due to the influence of the tropical sun, or perhaps to oxygenation 

 taking place under the stimulation of exposure to solar rays. This 

 has at first sight a measure of probability, since the color which 

 appears in tanning or freckles is not to be distinguished physio- 

 logically from the pigment which forms in the main body of the 

 skin of the darker races. The objection to this hypothesis is that 

 the covered portions of the body are equally dark with the ex- 

 posed ones, and that certain groups of men whose lives are pecul- 

 iarly sedentary, such as the Jews, who have spent much of their 

 time for centuries within doors, are distinctly darker than other 

 races whose occupations keep them continually in the open air. 

 This holds true whether in the tropics or in the northern part of 

 Europe. This local coloration in tanning, moreover, due to the 

 direct influence of the sun is not hereditary, as far as we can 

 determine. Sailors' children are not darker than those of the 

 merchant, even after generations of men have followed the same 

 profession. Each of these theories seems to fail as a sole explana- 

 tion. The best working hypothesis is, nevertheless, that this col- 

 oration is due to the combined influences of a great number of 

 factors of environment working through physiolof^ical processes, 

 none of which can be isolated from the others. One point is cer- 

 tain, whatever the cause may be that this characteristic has been 

 very slowly acquired, and has to-day become exceedingly persist- 

 ent in the several races. 



Study of the color of the skin alone has nothing further to 

 interest us in this inquiry than the very general conclusions we 

 have just outlined. We are compelled to turn to an allied charac- 



* Th. Waitz: Anthropologie der Naturvolker, vol. i, p. 55 seq., contains some interesting 

 remarks on this subject. 



