The medicine of the ancient Egyptians is some of the oldest documented. From the beginnings of the civilization in the late fourth millennium BC until the Persian invasion of 525 BC, Egyptian medical practice went largely unchanged but was highly advanced for its time, including simple non-invasive surgery, setting of bones, dentistry, and an extensive set of pharmacopoeia. Egyptian medical thought influenced later traditions, including the Greeks. Until the 19th century, the main sources of information about ancient Egyptian medicine were writings from later in antiquity. The Greek historian Herodotus visited Egypt around 440 BC and wrote extensively of his observations of their medicinal practice. Pliny the Elder also wrote favourably of them in historical review. Hippocrates (the "father of medicine"), Herophilos, Erasistratus and later Galen studied at the temple of Amenhotep, and acknowledged the contribution of ancient Egyptian medicine to Greek medicine.