Pre-ignition Pre-ignition Pre-ignition (or preignition) in a spark-ignition engine is a technically different phenomenon from engine knocking, and describes the event wherein the air/fuel mixture in the cylinder ignites before the spark plug fires. Pre-ignition is initiated by an ignition source other than the spark, such as hot spots in the combustion chamber, a spark plug that runs too hot for the application, or carbonaceous deposits in the combustion chamber heated to incandescence by previous engine combustion events. The phenomenon is also referred to as 'after-run', or 'run-on' or sometimes dieseling, when it causes the engine to carry on running after
Archaic humans of over 120 individuals. Dunbar argues that it was not possible for hominins to live in such large groups without using language, otherwise there could be no group cohesion and the group would disintegrate. By comparison, chimpanzees live in smaller groups of up to 50 individuals. Archaic humans A number of varieties of "Homo" are grouped into the broad category of archaic humans in the period contemporary to and predating the emergence of the earliest anatomically modern humans ("Homo sapiens") over 315 ka. The term typically includes "Homo neanderthalensis" (430+–38ka), "Denisovans", "Homo rhodesiensis" (300ka–125ka), "Homo heidelbergensis" (600ka–200ka), and "Homo antecessor".