Using glass flasks, Pasteur showed that previously boiled broths remained uncontaminated with microorganisms unless the neck of the flask was broken.Broken flasks quickly teemed with life as the broths became cloudy.Ernst Haeckel, one of the chief proponents of Darwinism, stated in 1876: "If we do not accept the hypothesis of spontaneous generation, then at this one point in the history of evolution we must have recourse to the miracle of a supernatural creation." The spontaneous generation debate heated up again in 1924 when Russian biochemist, I. Oparin proposed that life had arisen from simpler molecules on the lifeless earth under much different atmospheric conditions than exist today. In the nineteenth century Ernst Haeckel argued that although spontaneous generation was not observable under the current conditions on earth, it did take place in the past under different chemical conditions.However, instead of life arising suddenly, as previous spontaneous generation theories proposed, Oparin believed that it occurred over a very long period of time. Oparin and Haldane made the first serious proposals regarding those conditions.By the end of the nineteenth century, the majority of scientists believed that spontaneous generation was not possible.
Lightning, volcanic eruptions, sunlight, and deep oceanic volcanic vents are among the energy sources proposed to stimulate the necessary chemical reactions.
on the origin of life proposes that some four billion years ago, inanimate chemicals developed completely by chance into highly complex, living, single-celled organisms.
This process of life coming from non-life is called "spontaneous generation." According to the theory, a single-celled organism eventually evolved into all the complex life forms on earth in a relentless struggle for resources.
If the origin of life cannot be shown to be plausible by the interaction of matter, random chance, energy and time then the existence of an evolutionary tree is a dubious proposition at best. Without spontaneous generation there can be no evolution.
The notion that life could arise from inanimate, non-living matter is not a recent idea.