8 EVOLUTION MADE PLAIN 
Naturally, fossils of land animals are few 
compared with those of marine annuals. Practi¬ 
cally all the remains of the latter sank and 
wGie covered with the slowly accumulating 
sediment, while the bones of the former only 
rarely were swept out to sea and lake. Rarest 
or all fossils are those of man. A few have 
been found antedating history by several thou¬ 
sand years, but we get a far more complete 
knowledge of our primitive ancestors from the 
tools and weapons that they left in sediment 
and drift before the dawn of the present era. 
We can trace his progress upward through all 
degrees of culture from the rude old stone age 
of a hundred thousand years ago, through the 
new stone age, the copper and bronze age, and 
the iron age to the beginning of written records. 
Yet, so old is our planet and so long ago 
since life dawned on it—so long even since the 
first mammals appeared—that man’s arrival a 
hundred-or-so thousand years ago is but as yes¬ 
terday. To paraphrase an illustration by,Slade 
and Ferguson: “Suppose we take the earth 
as 365 million years old, and consider this 
period as a year, one million years being taken 
as a day.” Then, on this scale the vertebrates 
came into existence late in the summer or 
early fall, the mammals not earlier than the 
end of November, and “the whole period of 
man is not likely to have been further back 
than the evening of December 31st, and the 
earliest historic evidence (in Egypt) is not 
more than ten minutes before the last mid¬ 
night”—“the last midnight,” of course, being 
the present. 
