THE ANIMAL ANCESTRY OF MAN ^^ 



when he may have read elsewhere that scientists are still 

 disputing whether this or that particular fossil is or is not the 

 missing link. The argument may be compressed into the 

 following brief statement: When we study the recent and 

 fossil vertebrates as a whole, and when we study at the same 

 time the comparative anatomy of their organs, we fmd 

 that the vertebrates fall into larger and smaller natural 

 groups which may be arranged in the form of a tree, with 

 main trunk, boughs, branches, twigs and leaves. Mankind, 

 by all the evidence of comparative anatomy and kindred 

 sciences, belongs on one of the small twigs nearest to the 

 anthropoid apes; the man-ape branch surely belongs in the 

 Old World or catarrhine division of the Primates, and thus 

 the groups, one by one, may be traced down to the main 

 vertebrate trunk. 



Again, the record of fossilized organic remains, or palaeon- 

 tology, imperfect as it is, offers fully concordant evidence 

 that the main stages of ascent from fish to man have occurred 

 in the following order: 



I. Proterozoic ("Age of Primitive Life") 



1. Pre-Cambrian: first definite traces of hfe (algae, worm- 

 tubes, etc.). 



II. Palaeozoic ("Age of Invertebrates and Fishes") 



2. Cambrian: early stages of main phyla of invertebrates. 



3. Ordovician: first traces of fish-like forms. 



4. Silurian: earliest well-known fish-like forms (ostrac- 

 oderms). 



5. Devonian: lobe-fmned, air-breathing fishes. 



6. Lower Carboniferous: swamp-living amphibians. 



7. Upper Carboniferous: land-living primitive reptiles. 



8. Permian: mammal-like reptiles of several ascending 

 grades. 



III. Mesozoic ("Age of Reptiles") 



9. Triassic: cynodont reptiles or pro-mammals. 



10. Jurassic: archaic insectivorous mammals. 



11. Cretaceous: primitive placental insectivores. 



IV. Caenozoic ("Age of Mammals") 



12. Eocene: primitive lemuroid primates. 



13. Oligocene: proto-anthropoid stock. 



