452 SECTIONAL TRANSACTIONS.—H. 
gravels of these river and stream borders, subject to occasional floods and cloudbursts, 
are we likely to find the fossil remains of primitive man and of primitive elephants 
intermingled in the same fluviatile deposits. We recall that the Piltdown gravels of 
Sussex, obviously of low gradient and fluviatile origin, yielded fossil remains of 
Eoanthropus dawsoni intermingled with those of a supposed ‘ Stegodon,’ which now 
proves to be a true primitive Pliocene elephant, also with tooth fragments of a 
‘Mastodon,’ which now proves to be a highly characteristic Pliocene mastodon of the 
genus and species Anancus arvernensis. Again, in far-eastern Java, cranial and 
dental fragments of Pithecanthropus erectus were found in river-deposited sands and 
gravels associated with the remains of a primitive elephantoid known as Stegodon 
airawana, also with the more progressive elephantoid related to the Hlephas namadicus 
of the Siwaliks of India. Still more recently the Vaal River gravels of South Africa 
have yielded on lower and higher levels three elephantoids of the genus Archidiskodon, 
as recently described by the present author in Science, but no fossil human remains 
have thus far been found of equal antiquity with these primitive elephants of the Vaal 
River terraces. 
It follows that along elephant migration routes we may confidently look for 
human migration routes. There is also evidence that, prior to the Piltdown period, _ 
man hunted the elephant or the mastodon and used the bones in the fashioning 
of tools, but this disputed archzeological problem need not be discussed in the present 
paper. 
Our attention must now be devoted to the bearing which the association of fossil 
remains of man with those of primitive elephants or mastodons has upon the all- 
important question of the geologic antiquity of man. 
From closing Pliocene time onwards man and the elephants evolved side by side. 
While in man the grinding teeth were relatively stationary, in the elephants 
the elevation of the distinctive ridge plates composed of dentine, sheathed in 
enamel and bathed in cement, evolved with extraordinary chronologic precision within 
members of each generic phylum, at precisely the same rate whether in the same region 
or in widely separated regions. For example, we observe, as to the wide geographic 
distribution of the ancestral ‘ southern ’ or ‘ imperial’ mammoth such as Archidiskodon 
planifrons and Archidiskodon subplanifrons, that the ridge plates of a given geologic 
period correspond exactly in height whether measured in South Africa, in southern 
England, or in the Siwalik hills of India. Thus the evolution of the grinding teeth of 
primitive elephants afford an absolutely reliable chronometer whereby the antiquity 
of the successive stages of human evolution even in widely separated geographic 
regions can be precisely determined and correlated. 
The bearing on anthropology of these priceless enamel chronometers is nowhere 
more important than in helping us to determine the respective geologic ages of the 
Pithecanthropus of Java and the Hoanthropus of Piltdown. When Pithecanthropus 
was discovered it was almost unanimously regarded as of Pliocene or lower Pleistocene 
age. When Hoanthropus was discovered it was regarded as of undetermined lower to 
middle Pleistocene age. It now appears that both of these determinations are probably 
wrong. From the observations of Dubois, Dietrich, Freudenberg, Hopwood, 
Bather, and Osborn in his forthcoming Proboscidea Memoir, it would seem that — 
Pithecanthropus was the companion of Stegodon airawana and Paleoloxodon namadicus, 
hence of middle Pleistocene age; Hoanthropus dawsoni was the companion of 
Archidiskodon planifrons and Anancus arvernensis, hence of upper Pliocene or lower 
Pleistocene age. - 
The new preliminary ganometric estimates of the age of the known fossil men and _ 
their contemporary flint industries or cultures are as follows :— 
i a 
Eoanthropus dawsoni - - 3 - 1,000,000 Pre-Chellean. 
Paleanthropus heidelbergensis . : : 920,000 Pre-Chellean. 
Sinanthropus pekingensis, of China. 3 920,000 Unknown. 
Pithecanthropus erectus, of Java . : 500,000 Unknown. 
Paleanthropus neanderthalensis, of Ehrings- 
dorf - 5 , : : . 
Paleanthropus neanderthalensis, of Nean- 
derthal 3 5 : : 70,000 Mousterian. 
Homo sapiens cromagnonensis . : : 30,000 Magdalenian. 
Homo sapiens nordicus, of S. Scandinavia . 12,000 Campignian. 
135,000 Pre-Mousterian. 
