Geological Aspects of Evolution 103 
Germany. On this basis, Father Richarz concluded that the mini- 
mum figure for the existence of man is 19,000 years plus 11,000 
years, which equats 30,000 years. Father Richarz regarded this 
figure as a minimum, for many authorities including Hugo Ober- 
maier, Abbé Breuil, Father Teilhard de Chardin, S.J., G. Elliot 
Figure 4. 
N §—/OWA—w1 $ Central towa sibel 
TooAY — Tay 
2 W 2Seqoyears | o SARS Southeastern lowa 1° 
= z PEORIAY 4 "Yin 6 
s a2 31000 years | > Q “s* oO, 
WISCONSIN 
100,000 — fe) 
SANGAMON fa) e = | 
120,000 years 
200,000 — rm 
30.000 — 
s Cc YARMOUTH 
300,000 years 
400.000 — 
HI ly ae Hs 
be dee 
500,000 — 
baie’ 1 fe) oO Pre) ° 
HSI H Tey 
600, 009 — AP TONIAN enasebeenet . 
200,000 years a umbotil 04 
i Q e - 1” 
Nee ase fa) a. 64 Till Gravels in gravels ad 
Figure 4: Minimum Duration of Pleistocene Period in Iowa. After G, F, Kay. 
Based on relative depths of leaching in upland gravels. The diagram indicates 
relative depths of leaching of upland gravels in Iowa and the estimates of 
minimum duration of glacial and interglacial ages and of the 
as a whole. 
Pleistocene Period 
Smith and Henry F. Osborn consider that man existed during 
the earliar interglacial stages. As a consequence this figure must 
be increased many times, if it is to include the earliest record 
of fossil man. 
