The purpose of this research was to examine the use and modification o
f stone tools by tufted capuchin monkeys (Cebus apella). Two experimen
ts were conducted. In Experiment 1, six of 11 monkeys produced stone-f
lakes, by striking stones against hard surfaces. In Experiment 2, thre
e of 15 monkeys used stones as cutting tools. Two of these monkeys com
bined tools and one of them modified stones prior to using them as too
ls. The results of this study demonstrate a simple stone-tool technolo
gy in monkeys. These data provide further evidence for cross-species c
ontinuity in the tool-using and tool-making abilities of primates and
indicate that stone-tool technology may have evolved in the hominid li
neage earlier than has been confirmed by the existing archaeological r
ecord.