Interestingly, the most recent 3500 years of prehistory was a time of Native American population growth and sociopolitical changes, perhaps increased human - induced fire, as well as a period of climatic instability [41,42], both of which could have affected contemporary levels of mtDNA diversity. (journals.plos.org)
ABSTRACT (Lean 2000): Because of the dependence of the Sun's irradiance on solar activity, reductions from contemporary levels are expected during the seventeenth century Maunder Minimum. (junksciencearchive.com)
Revised existing drawings of aerospace related parts and assemblies to contemporary levels using AutoCAD and occasionally Pro / E. (jobhero.com)