A variety of theories regarding the origins of pre-colonial Canarians explain them by the hypothesis of a more recent immigration. Some scholars (mainly from the University of La Laguna, in Tenerife) defend the theory that the Canarian populations are Punic-Phoenician in origin. Professor D. Juan Álvarez Delgado, on the other hand, argued that the Canaries remained uninhabited until 100 BCE, when Greek and Roman sailors began to explore the area. In the second half of the 1st century BCE, King Juba II of Numidia abandoned North African prisoners on the islands, who eventually became the pre-Hispanic Canarians. If the first inhabitants were abandoned prisoners, this explains, according to Álvarez Delgado, their lack of navigational acumen.