THE LINEAGE OF MAN 



be little doubt as to their relatively close relationship. The 

 alternative possibilities, either that fishes were derived from 

 four-footed amphibious animals, much as v^hales have been 

 derived from mammals, or that air-breathing fishes and four- 

 footed animals represent entirely distinct groups of verte- 

 brates, have been carefully considered by those best qualified 

 to vv^eigh the evidence and have been rejected for excellent 

 reasons. 



We must infer, then, that some adventurous pioneers 

 among the early air-breathing fishes managed to crawl out 

 of the muddy waters at times when either the supply of 

 oxygen in the water or the supply of living food there was 

 insufficient; that at such times these creatures wriggled along 

 on their bellies much as some eel-like fishes do now under 

 similar circumstances, except that they used the stout fore 

 and hind paddles to increase their hold on the mud and to 

 assist in pushing the body forward. From that time on, 

 the stout fan-shaped fore-paddles began to be bent at the 

 future elbows and wrists, while the hind paddles were bent 

 in the opposite directions at the future knees and ankles; 

 meanwhile the fan-shaped bony rods of the paddles broke 

 into segments and gave rise to the bones of the fingers and 

 toes. 



In many of the earliest land-living vertebrates there were 

 five principal rods or digits on each hand and foot, and 

 possibly a small nodule or reduced ray in front of the thumb 

 or the great toe, and another behind the little finger 

 or the little toe; but these extra digits in most lines of 

 animals were early reduced to vestiges, so that the five- 

 rayed hand and foot became the standard form. Thus 

 man in common with other vertebrates has inherited the 

 basic pattern of his five-fingered hand and five-toed foot 

 from the earliest land-living vertebrates, perhaps of the days 



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