Ignition timing Ignition timing In a spark ignition internal combustion engine, Ignition timing refers to the timing, relative to the current piston position and crankshaft angle, of the release of a spark in the combustion chamber near the end of the compression stroke. The need for advancing (or retarding) the timing of the spark is because fuel does not completely burn the instant the spark fires, the combustion gases take a period of time to expand and the angular or rotational speed of the engine can lengthen or shorten the time frame in which the burning and expansion should occur. In a
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".