Afterthearrivalofhunter-gatherersinthesouthwesternregionofNorthAmerica,severalalternativetypesofagricultureemerged,allinvolvingdifferentsolutionstotheSouthwest’sfundamentalproblem:howtoobtainenoughwatertogrowcropsinanenvironmentinwhichrainfallissolowandunpredictablethatlittleornofarm