hrdliCka] GENEEAL CONSIDEEATIONS 7 



orJy secondarily and in a very uncertain manner of the time required 

 for the consummation of the changes. 



Alterations produced in different bones are often seen to be alike, 

 even though the specimens come from different localities and sometimes 

 from apparently different investing conditions. Tliis is explainable 

 only on the assumption that the real conditions in the different places 

 were similar. As the whole process of post-mortem change in bone 

 is largely of the nature of chemical reactions, it will always lead, with 

 the same elements, to much the same result. But such similarity of 

 modification is no index of the quantity of the available reagents, of 

 the facility of their action, or of the period during which they acted 

 in the various cases and places, and hence alone is no measure of 

 time. Two bones that show a hke degree of "fossilization" are 

 therefore not necessarily contemporaneous or even nearly so. This 

 applies even to bones from the same locahty, for some may have been 

 subjected, through differences in depth or locahzed variation in soil 

 or amount of moisture, to considerably different influences. For the 

 same reason even the two extremities of the same bone may present 

 differences in color, weight, and in other qualities. 



Another important point is that each locality, each kind of soil, 

 must necessarily have a limit to its possible effect on a bone, or at 

 least there must be a point beyond which further alterations in the 

 bone, unless new conditions set in, are extremely slow. Such limit 

 reached, the bone may continue in the same place for ages as an inert, 

 neutral object, and resemble closely other bones from the same cave, 

 layer, or deposit, introduced at a much later time, but which hkewise 

 may have reached the limit or nearly the limit of their possible altera- 

 tions under the local conditions. 



The above facts demonstrate the futility of utilizing alterations in 

 bones as a chronologic index. Yet it is this very unreliable factor of 

 "fossihzation" of human bones that is principally responsible for the 

 "peopling" of North America, and especially of South America, with 

 "fossil" ancient human forms. 



The foregoing considerations make it clear that while geologically 

 ancient bones may be confidently expected to show more or less 

 decided alterations of both organic and inorganic nature,* such 

 alterations alone can never become a criterion of antiquity. 



In conclusion, it is necessary to refer to a certain class of other 

 phenomena observed occasionally in connection with human and 

 especially with animal bones, and sometimes brought forward as 

 proofs of man's antiquity. This applies to the split or splintered 

 bones and to those that show various scratches, striae, cuts, or perfo- 

 rations, which appear to be due possibly to human agency. 



' In very rare instances remains of some of tlie most recent but now extinct animals tiave been found 

 apparently but little altered, but the date of death in these few cases has never been accurately determined. 



