The Consequences of Evolution - 559 



Fig. 29-4. Probable interrelations of the primates, and the fossil forms most closely in the 

 line of human ancestry. 



ferent phyla, have been classified in accord- 

 ance with their blood and tissue reactions, 

 and generally speaking, these tests indicate 

 the same relationships as were derived from 

 structural and developmental studies. Thus 

 these biochemical relations — which were dis- 

 covered long after the theory of evolution 

 had gained general acceptance — strikingly 

 confirm the conclusions that were based 

 originally upon totally different grounds. 

 Apparently the biochemical similarities be- 

 tween related species come from the same 

 sources as their structural and developmental 

 similarities — the possession of a common 

 fund of genes derived from a common an- 

 cestry. 



PALEONTOLOGY: THE FOSSIL RECORD 



A fossil is any sort of remnant, or trace, 

 left by an ancient pre-existing form of life 



Fig. 29-5. The serum of a rabbit "immunized" with 

 wolf blood will cause a heavy precipitate of the pro- 

 teins of wolf plasma when this plasma is added to the 

 rabbit serum in a test tube. The chemically similar 

 proteins of dog blood give a faint precipitate, but 

 the quite different ones of cat blood react scarcely at 

 all. (From Gerard, Unresting Cells. Permission of 

 Harper and Row.) 



