ITS–The “Perning I”fossil, also called Pithecanthropus modjokertensis or robustus, was found by Tjokrohandojo, who worked under the supervision of Duyfjes, in 1936 in Perning Village, Mojokerto, East Java. The skull is thought to have belonged to a six year old child. The fossil is the oldest of all Pithecanthropus race living in the Pleistocene age in Indonesia. It is thought to be 1.9 million years old.
There were many other fossils of the race later found in other places in Indonesia. Based on all the finds, experts have judged that the race had robust physics, a projected face and strong muscles at the nape of neck. Still, they were less robust than Meganthropus paleojavanicus, the most primitive race ever discovered in Indonesia. Pithecanthropus modjokertensis were omnivorous. They lived between 2.5 and 1.5 million years ago, around at the same time Meganthropus lived.