population of Aus pre-colonisation was estimated 750,000.
Massacres of First Nations people often took the form of mass shootings or driving groups of people off cliffs. There are also numerous accounts of colonists offering First Nations people food laced with arsenic and other poisons.[6]
"In less than twenty years we have nearly swept them off the face of the earth. We have shot them down like dogs. In the guise of friendship we have issued corrosive sublimate in their damper and consigned whole tribes to the agonies of an excruciating death. We have made them drunkards, and infected them with diseases which have rotted the bones of their adults, and made such few children as are born amongst them a sorrow and a torture from the very instant of their birth. We have made them outcasts on their own land, and are rapidly consigning them to entire annihilation."
https://australianstogether.org.au/discover/australian-history/colonisation/
Edward Wilson (Editor), The Argus, 17 March 1856[7]
