Non-contact optical 3D-profiling instruments are often used in the study of surface modifications on fossil mammalian bone. The advantage of optical laser scanning for the study of fossil and sub-fossil bone is its non-contact nature, allowing the investigation of fragile and poorly preserved surfaces. The high resolution and fast measuring rate of this method make it an alternative to scanning electron microscopy (SEM) investigation if topography is to be visualized. This study analyses clusters of incisions in a suid humeral fragment from the Pliocene Upper Laetolil Beds. The marks show a characteristic crest structure that is also frequently found in mandible marks produced by the Australian termite species Mastotermes darwiniensis. The marks from the Laetolil Beds are, therefore, interpreted as also being caused by insect mandible action. An as yet unknown large insect species capable of modifying bone with their mandibles is thus postulated in the palaeohabitat represented by the hominid-bearing Upper Laetolil Beds. Copyright © 2001 John Wiley & Sons, Ltd.