Populations remain stable over millennia unless flooded with refugees.
“Humans & Society: DNA Reveal Canaanites’ Fate; Lebanese People Descended From Ancient Levant Group”, in Science News, September 2, 2017. p. 8.
Study of complete DNA sequences from five ancient Canaanites from Sidon reveal that they are the ancestors of modern Lebanese. The origins of the Canaanites have been disputed among the many surviving ancient recorded. However, the reconstructed DNA of five Canaanites who lived near Sidon 3700 years ago, and comparison with other Eurasian populations, indicates that Lebanese ancestry was split between indigenous Levantine agriculturalists and immigrants from Iran, who arrived 3500-6600 years ago. Such a large impact would require a sizable migration. Speculatively, one possible event that could have triggered such an immigration/refugee influx is the collapse of the Akkadian Empire, 4200-4400 years ago.
Some 93% of modern Lebanese DNA comes from this ancient Canaanite mix, with the remaining 7% mainly coming from another Eurasian influx 2200-3700 years ago.
The next step is studies of more ancient Canaanite genomes.