These crude tools were around for thousands of centuries, until around 1.4 million years ago when Homo erectus started shaping single, thin stone blades, sometimes rounded ovals, but often in what are to our eyes an arresting, symmetrical pointed leaf or teardrop form.
Šie primitīvie darbarīki tika lietoti tūkstošiem gadsimtu ilgumā, līdz apmēram 1,4 miljonu gadu atpakaļ, kad Homo erectus sāka veidot plānus akmens asmeņus, reizēm noapaļotus, bet parasti, no mūsu viedokļa, burvīgas, simetriski smailas lapas vai piliena formā.