in the united states, the first ancient south american culture to be studied thoroughly was that of the central american maya. the most notable works were the classical studies of v. h. spratles and f. j. weitsman,  the beautiful publications of the museo de anthropologia in mexico, with which i was associated as collaborator of the revista mexicana de estudios indigenas, were very stimulating and gave several new light on the civilization of the indians in mexico.
the most recent work on the subject in this country, however, is that by the geologist, n. heizer, on the south american archeo-flora published by the university of california press in berkeley. (not to be confused with the well-known botanical and geological publications of this same university.)  a new development in this field is the attempt to use the recent methods of palynology to trace the climatic conditions and the earth cycles that may have had an influence on the development of human civilization.
a total of 98 studies were reviewed; 79 were excluded. of the remaining 19 studies, 7 studies were excluded (further details and results are available from the corresponding author) and 12 were included in the meta-analyses: 4 rcts (n = 2 418) and 8 observational studies (n = 4 461). the overall odds ratio for hyperkalaemia was 0.34 (95% ci 0.28 to 0.41; p < 0.00001; i2 = 4%; 6 studies) with no evidence of publication bias. the overall md in change from baseline serum potassium was -0.32 mmol/l (95% ci -0.59 to -0.05; p = 0.02; n = 8 studies) with no evidence of publication bias. the pooled or for death was 2.63 (95% ci 0.91 to 7.54; p = 0.07). the pooled or for esrd was 0.65 (95% ci 0.41 to 1.02; p = 0.06; n = 6 studies). 3d9ccd7d82