Page:American Journal of Sociology Volume 3.djvu/423

 REVIEWS 409

implies no idea of progression or regression but denotes all forms of transformation, whether favorable or unfavorable, and state their gen- eral conclusions as follows :

1. All evolution is at once progressive and regressive. The transformations of organs and of institutions are always accompanied by regression. The same is true of transformations of organisms and of societies : all existing forms, organic or social, have undergone transformations, and in consequence of these transformations have lost certain portions of their structure. This universality of regressive evo- lution may be proven either by comparison or by showing that all organisms bear reduced organs and that all societies contain survivals.

2. Regressive evolution does not operate in a predetermined order and does not involve a return to a primitive state. It is sometimes true when the same cause of dissolution operates with equal intensity upon all parts of an institution or organism that the most complex and fragile structures disappear first ; but we cannot frame a general law that the most complex structures are at the same time the most recent, and that regression consequently transpires uniformly in the inverse order of progression. When an institution or an organ once disappears it does not reappear. An institution or an organ reduced to a vestigeal state cannot develop anew and resume its former func- tions, and cannot assume new functions.

3. Regressive evolution is caused by a limitation of means of subsistence nutriment, capital or labor. In biology its principal or sole factors are the struggle for existence between organs and the struggle for existence between organisms. In sociology artificial selection plays a preponderant r61e, natural selec- tion a secondary r61e. Occasional causes of regressive evolution are inutility of function, insufficient nutrition or resources, and (in biology alone) lack of space. An institution or an organ which has ceased to function and lost its utility, direct or indirect, may nevertheless persist if one or the other of the factors of atrophy variability or selection -does not operate. WILLIAM I. THOMAS.