Clothing:

Scientists are still debating when people started wearing clothes. Ralf Kittler, Manfred Kayser and Mark Stoneking, anthropologists at the Max Planck Institute for Evolutionary Anthropology, have conducted a genetic analysis of human body lice that suggests clothing originated quite recently, around 170,000 years ago. Body lice is an indicator of clothes-wearing, since most humans have sparse body hair, and lice thus require human clothing to survive. Their research suggests the invention of clothing may have coincided with the northward migration of modern Homo sapiens away from the warm climate of Africa, thought to have begun between 50,000 and 100,000 years ago. However, a second group of researchers using similar genetic methods estimate that clothing originated around 540,000 years ago (Reed et al. 2004. PLoS Biology 2(11): e340). For now, the date of the origin of clothing remains unresolved.[citation needed]

Please answer a question about this article. If the question is unanswerable, say "unanswerable". Southward migration coincided with what?
unanswerable