﻿POPULATION 
  OF 
  ANCIENT 
  AMERICA 
  SPINDEN 
  

  

  461 
  

  

  dependent 
  upon 
  the 
  second 
  plane 
  of 
  distribution.^^ 
  In 
  general 
  this 
  

   follows 
  Harshberger's 
  botanical 
  evidence 
  on 
  the 
  dissemination 
  of 
  

   maize. 
  *^ 
  In 
  Mexico 
  and 
  Central 
  America 
  there 
  is 
  a 
  safe 
  priority 
  of 
  

   several 
  thousand 
  years 
  for 
  arid-land 
  agriculture, 
  and 
  some 
  of 
  the 
  

   plants 
  domesticated 
  under 
  the 
  regime 
  of 
  irrigation 
  spread 
  to 
  the 
  very 
  

   limits 
  of 
  the 
  New 
  World 
  agricultural 
  area. 
  The 
  staple 
  plants 
  were 
  

   modified 
  to 
  meet 
  humid 
  conditions 
  probably 
  under 
  the 
  stimulus 
  of 
  a 
  

   pressure 
  of 
  population 
  on 
  food 
  supply 
  which 
  induced 
  farmers 
  to 
  

  

  FiouKK 
  4.— 
  Map 
  showing 
  sites 
  o( 
  ruins 
  of 
  the 
  Second 
  Mayan 
  Empire 
  with 
  the 
  high 
  development 
  in 
  

  

  northern 
  Yucatan 
  

  

  invade 
  the 
  wet 
  forests. 
  On 
  the 
  other 
  hand, 
  the 
  new 
  plants 
  domesti- 
  

   cated 
  in 
  humid 
  habitats 
  had 
  only 
  a 
  restricted 
  distribution 
  and 
  were 
  

   never 
  developed 
  to 
  meet 
  dry 
  conditions; 
  witness 
  cacao, 
  manioc, 
  and 
  

   pineapples. 
  Perhaps 
  the 
  most 
  widely 
  distributed 
  plants 
  of 
  the 
  wet 
  

   lands 
  were 
  sweet 
  potatoes 
  and 
  peanuts, 
  both 
  capable 
  of 
  being 
  grown 
  in 
  

   temperate 
  regions. 
  

  

  »' 
  H. 
  J. 
  Spinden: 
  The 
  Origin 
  and 
  Distribution 
  of 
  Agriculture 
  in 
  America, 
  Proc. 
  19th 
  Internatl. 
  Congr. 
  

   of 
  Americanists, 
  Held 
  at 
  Washington, 
  Dec. 
  27-31, 
  1915, 
  pp. 
  269-276, 
  Washington, 
  1917. 
  

  

  i« 
  J. 
  W. 
  Harshberger: 
  Maize: 
  A 
  Botanical 
  and 
  Economic 
  Study, 
  Contr. 
  Bot. 
  Lab. 
  Univ. 
  of 
  Pennsyl- 
  

   vania, 
  Vol. 
  1, 
  No. 
  2, 
  Philadelphia, 
  1893. 
  

  

  