Passage: The first major technological development, Bugatti's re-introduction of mid-engined cars (following Ferdinand Porsche's pioneering Auto Unions of the 1930s), occurred with the Type 251, which was unsuccessful. Australian Jack Brabham, world champion during 1959, 1960, and 1966, soon proved the mid-engined design's superiority. By 1961, all regular competitors had switched to mid-engined cars. The Ferguson P99, a four-wheel drive design, was the last front-engined F1 car to enter a world championship race. It was entered in the 1961 British Grand Prix, the only front-engined car to compete that year.During 1962, Lotus introduced a car with an aluminium-sheet monocoque chassis instead of the traditional space-frame design. This proved to be the greatest technological breakthrough since the introduction of mid-engined cars. During 1968, Lotus painted an Imperial Tobacco livery on their cars, thus introducing sponsorship to the sport.Aerodynamic downforce slowly gained importance in car design from the appearance of aerofoils during the late 1960s. During the late 1970s, Lotus introduced ground-effect aerodynamics (previously used on Jim Hall's Chaparral 2J during 1970) that provided enormous downforce and greatly increased cornering speeds. So great were the aerodynamic forces pressing the cars to the track (up to five times the car's weight), extremely stiff springs were needed to maintain a constant ride height, leaving the suspension virtually solid, depending entirely on the tyres for any small amount of cushioning of the car and driver from irregularities of the road surface.

Question: When did Lotus introduce aerodynamics
the late 1970s