Sighthounds such as the saluki/sloughi type (both named after the Seleucid Empire) have existed for at least 5,000 years, with the earliest presumed sighthound remains appearing in the excavations of Sumer dated approximately 7000–6000 BC. The earliest description of a sighthound in European recorded history comes from Arrian's Cynegeticus, of the 2nd century AD. Although today most sighthounds are kept primarily as pets, they have been bred for thousands of years to detect movement, chase, capture, and kill prey primarily by speed. They thrive on physical activity. Some have mellow personalities, others are watchful or even hostile towards strangers, but the instinct to chase running animals remains strong.