Even more intriguing than their vast distribution across three continents is their time depth. Acheulean hand axes have been found at sites spanning 1.5 million years of human existence, dating from roughly 1.6 million years ago to about 100,000 years ago. That makes the Acheulean ax the most sustainable technology that members of our genus (Homo) ever developed. Consider, in contrast, the amount of technological change that has occurred in just the last 150 years (since the first telephone call), one ten-thousandth the amount of time the Acheulean hand ax was made and used. Or consider the amount of technological change in just the last 10 years (since the first iPhone was introduced), one one-hundred-fifty-thousandth the amount of time that Acheulean hand axes were made and used. In the memorable words of my former professor Arthur J. Jelinek, hand axes represent “mind-numbing technological stability.”