translation.en: 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.
translation.zh: 这类粗糙的工具 存在了数千个世纪， 直到大约一百四十万年前， 直立人 开始打磨 单个的薄石刀片， 有时是椭圆形的， 但通常，在我们眼中， 是醒目的对称的尖叶子形 或泪滴形。