414 THE INSCRIPTIONS AT COPAN. 
the remaining 11, on stylistic grounds 4 are surely earlier than Stela 3,! 
3 as early,? and only 3 are later.* That is to say that whereas at Copan we 
have only 1 stela (Stela 20) which may be earlier than 9.2.10.0.0 (Stela 24), 
at Tikal we have at least 4 (Stele 4, 7, 8, and 13), and possibly 3 more 
(Stele 1, 2, and 9), which are earlier than 9.2.13.0.0 (Stela 3). 
This evidence at Tikal, coupled with that at Uaxactun, where we have 
one monument (Stela g) if not two (Stela 5) recording dates actually 140 
years earlier than the earliest possible contemporaneous date now known 
at Copan, proves on the chronologic side almost conclusively that Uaxactun- 
Tikal is considerably older than Copan. This is established not only by the 
actual priority of the Uaxactun dates, but also by the mass of the evidence, 
more earlier monuments being known at Tikal, although not exactly dated, 
than at Copan. 
Finally, the geographic location of these two great Maya centers is such 
as to make it extremely probable that Tikal is the older. Not only is Tikal 
nearer the center of the Old Empire, and Copan far out on the southeastern 
frontier (see plate 1), but also the general trend of early Maya migration 
was from northwest to southeast, the earliest dated Maya object known 
being found 300 kilometers nearer Tikal than Copan. 
Summing up these several lines of evidence as to the origin of the Maya 
civilization, it appears as not improbable that the introduction of agricul- 
ture from the highlands of central Mexico to the Gulf Coast-plain may have 
been the primary factor in releasing the Maya from complete absorption in 
the continuous struggle for bare existence. 
Cultivation applied to this naturally rich region yielded a far more 
abundant return than in the arid highlands, and the exigencies of the agri- 
cultural year, the clearing, planting, and harvesting seasons, must soon have 
turned the minds of the Maya priesthood toward the accurate measure of 
time and the study of the seasonal year and of the sun and moon. 
After many generations of recorded observations on these bodies, cer- 
tain natural laws became deducible therefrom, and then some Mayan 
Hipparchus invented the calendar, possibly first a 260-day Sacred Year (the 
tonalamatl) built up on the permutation of 13 numbers and 20 names, per- 
haps next a 365-day solar year (the haab), composed of 18 periods of 20 
days each and a closing period of 5 days, and still later a combination of the 
two, in which the 260 differently named days were fitted into the 365 posi- 
tions of the year, giving a new period (the Calendar Round) composed of 
18,980 dates, 52 years of 365 days each or 73 years of 260 days each. Still 
later some one devised the remarkable Maya vigesimal numerical system, 
numeration by position, 7. ¢., from bottom to top, and the ingenious Maya 
arithmetical notation of bars and dots, and probably later the head-variant 
numerals, and thus the calendar and chronology gradually took shape. 
Some time prior to these discoveries, however, the Maya would seem 
to have begun a general movement southeastward, in which the possibly 

1 Stele 4, 7, 8, and 13. 2 Stelz 1, 2, and 9. 3Stela 10, 12, and 17 
