Spontaneous Generation

Spontaneous generation, also called abiogenesis, is the belief that some living things can arise suddenly, from inanimate matter, without the need for a living progenitor to give them life.

In the fourth century BC, the Greek philosopher and scientist Aristotle argued that abiogenesis is one of four means of reproduction, the others being budding (asexual), sexual reproduction without copulation, and sexual reproduction with copulation. Indeed, the Greek goddess Gea was said to be able to create life from stones. Even Albertus Magnus (Albert the Great), the great German naturalist of the thirteenth century Middle Ages, believed in spontaneous generation, despite his extensive studies of the biology of plants and animals.

Through the centuries, the notion of spontaneous generation gave rise to a wide variety of exotic beliefs, such as that snakes could arise from horse hairs standing in stagnant water, mice from decomposing fodder, maggots from dead meat, and even mice from cheese and bread wrapped in rags and left in a corner. The appearance of maggots on decaying meat was especially strong evidence, for many people, that spontaneous generation did occur.

Spontaneous generation found further support from the observations of the Dutch merchant Anton van Leewenhoek, the inventor of the first, primitive microscopes. From 1674 to 1723 Leewenhoek corresponded to the Royal Society in London, describing the tiny, rapidly moving, “animacules” he found in rain water, in liquid in which he had soaked pepper-corn, and in the scrapings from his teeth (which, to Leeuwenhoek’s surprise, had no such animacules after he had drunk hot coffee).

In the seventeenth century, however, some scientists set out to determine whether living organisms could indeed arise through spontaneous generation, or if they arose only from other living organisms (biogenesis).

In 1668, even before Anton van Leeuwenhoek began his study of microscopic organisms with the microscope, the Italian physician Francisco Redi began a series of experiments that showed that dead meat does not give rise spontaneously to maggots.

Redi filled six jars with decaying meat, leaving three open and sealing the other three. The unsealed jars attracted flies, which laid their eggs on the decaying meat, while the meat in the sealed jars was unavailable to flies. When maggots developed on the meat in the open jars, Redi believed he had demonstrated that spontaneous generation did not ocur. However, supporters of the notion of spontaneous generation claimed that the lack of fresh air—not the absence of egg-laying flies—had prevented maggots from appearing on the meat.

Therefore, Redi undertook a second experiment, in which he covered the tops of three of the jars with a fine net instead of sealing them. Once again, maggots failed to appear on the meat in the covered jars, but did appear on the meat in the open jars, where flies were able to lay their eggs.

Nevertheless, the tiny “animacules,” described by Leeuwenhoek in his observations on microscopic life in drops of water, still held the imagination of many scientists, who continued to believe that such creatures were small and simple enough to be generated from nonliving material.

John Needham, an eighteenth century English naturalist and Roman Catholic theologian, began his study of natural science after reading about Leewenhoek’s animacules. Needham became a strong advocate of spontaneous generation, and performed an experiment that he felt supported his belief in biogenesis. In 1745, he heated chicken and corn broths, poured them into covered flasks. Soon after the broths cooled, they teemed with microorganisms, prompting Needham to claim that the organisms arose through spontaneous generation.

Needham’s work was contradicted by another religious investigator, the Italian physiologist Lazzaro Spallanzani. Spallanzani, who was educated in the classics and philosophy at a Jesuit college, went on to teach logic, metaphysics, Greek, and physics. About 20 years after Needham announced the results of his own investigation of spontaneous generation, Spallanzani showed that when broth was heated after being sealed in a flask, it did not generate life forms. He suggested that Needham’s broths had probably supported growth after being heated because they had been contaminated before being sealed in their containers.

Undeterred, Needham counterclaimed that heat destroyed the “vital force” needed for spontaneous generation, and that, by sealing the flasks, Spallanzani had kept out this vital force.

The argument continued into the nineteenth century, when the German scientist Rudolf Virchow in 1858, introduced the concept of biogenesis; living cells can arise only from preexisting living cells.

But the matter remained unresolved until two years later when the great French scientist Louis Pasteur, in a series of classic experiments demonstrated that (1) microorganisms are present in the air and can contaminate solutions; and (2) the air itself does not create microbes.

Pasteur filled short-necked flasks with beef broth and boiled them, leaving some opened to the air to cool and sealing others. While the sealed flasks remained free of microorganisms, the open flasks were contaminated within a few days.

In a second set of experiments, Pasteur placed broth in flasks that had open-ended, long necks. After bending the necks of the flasks into S-shaped curves that dipped downward, then swept sharply upward, he boiled the contents. The contents of these uncapped flasks remained uncontaminated even months later. Pasteur explained that the S-shaped curve allowed air to pass into the flask; however, the curved neck trapped airborne microorganisms at the bottom of the curve, preventing them from traveling into the broth.

Pasteur not only executed a brilliant set of experiments, he also used his zeal and skill as a promoter of his ideas to strike a decisive blow to spontaneous generation. For example, in a lecture at the Sorbonne in Paris in 1864, Pasteur said that he had water for his experimental liquids to generate life. But, he said, “. …it is dumb, dumb since these experiments were begun several years ago; it is dumb because I have kept it sheltered from the only thing man does not know how to produce, from the germs which float in the air, from Life, for Life is a germ and a germ is Life. Never will the doctrine of spontaneous generation recover from the mortal blow of this simple experiment!” Pasteur’s work not only disproved abiogenesis, but also offered support to other researchers attempting to show that some diseases were caused by microscopic life forms. Thus, in a simple, but elegant set of experiments, Pasteur not only struck the doctrine of spontaneous generation a “mortal blow,” but also helped to establish the germ theory of disease.

Marc Kusinitz

Spontaneous generation

Spontaneous generation, also called abiogenesis, is the belief that some living things can arise suddenly, from inanimate matter , without the need for a living progenitor to give them life.

In the fourth century b.c., the Greek philosopher and scientist Aristotle argued that abiogenesis is one of four means of reproduction, the others being budding (asexual), sexual reproduction without copulation, and sexual reproduction with copulation. Indeed, the Greek goddess Gea was said to be able to create life from stones. Even Albertus Magnus (Albert the Great), the great German naturalist of the thirteenth century Middle Ages, believed in spontaneous generation, despite his extensive studies of the biology of plants and animals.

Through the centuries, the notion of spontaneous generation gave rise to a wide variety of exotic beliefs, such as that snakes could arise from horse hairs standing in stagnant water , mice from decomposing fodder, maggots from dead meat, and even mice from cheese and bread wrapped in rags and left in a corner. The appearance of maggots on decaying meat was especially strong evidence, for many people, that spontaneous generation did occur.

Spontaneous generation found further support from the observations of the Dutch merchant Anton van Leewenhoek, the inventor of the first, primitive microscopes. From 1674 to 1723 Leewenhoek corresponded to the Royal Society in London, describing the tiny, rapidly moving, "animacules" he found in rain water, in liquid in which he had soaked peppercorn, and in the scrapings from his teeth (which, to Leeuwenhoek's surprise, had no such animacules after he had drunk hot coffee).

In the seventeenth century, however, some scientists set out to determine whether living organisms could indeed arise through spontaneous generation, or if they arose only from other living organisms (biogenesis).

In 1668, even before Anton van Leeuwenhoek began his study of microscopic organisms with the microscope , the Italian physician Francisco Redi began a series of experiments that showed that dead meat does not give rise spontaneously to maggots.

Redi filled six jars with decaying meat, leaving three open and sealing the other three. The unsealed jars attracted flies , which laid their eggs on the decaying meat, while the meat in the sealed jars was unavailable to flies. When maggots developed on the meat in the open jars, Redi believed he had demonstrated that spontaneous generation did not occur. However, supporters of the notion of spontaneous generation claimed that the lack of fresh air-not the absence of egg-laying flies-had prevented maggots from appearing on the meat.

Therefore, Redi undertook a second experiment, in which he covered the tops of three of the jars with a fine net instead of sealing them. Once again, maggots failed to appear on the meat in the covered jars, but did appear on the meat in the open jars, where flies were able to lay their eggs.

Nevertheless, the tiny "animacules," described by Leeuwenhoek in his observations on microscopic life in drops of water, still held the imagination of many scientists, who continued to believe that such creatures were small and simple enough to be generated from nonliving material.

John Needham, an eighteenth century English naturalist and Roman Catholic theologian, began his study of natural science after reading about Leewenhoek's animacules. Needham became a strong advocate of spontaneous generation, and performed an experiment that he felt supported his belief in biogenesis. In 1745, he heated chicken and corn broths, poured them into covered flasks. Soon after the broths cooled, they teemed with microorganisms , prompting Needham to claim that the organisms arose through spontaneous generation.

Needham's work was contradicted by another religious investigator, the Italian physiologist Lazzaro Spallanzani. Spallanzani, who was educated in the classics and philosophy at a Jesuit college, went on to teach logic, metaphysics, Greek, and physics . About 20 years after Needham announced the results of his own investigation of spontaneous generation, Spallanzani showed that when broth was heated after being sealed in a flask, it did not generate life forms. He suggested that Needham's broths had probably supported growth after being heated because they had been contaminated before being sealed in their containers.

Undeterred, Needham counterclaimed that heat destroyed the "vital force" needed for spontaneous generation, and that, by sealing the flasks, Spallanzani had kept out this vital force .

The argument continued into the nineteenth century, when the German scientist Rudolf Virchow in 1858, introduced the concept of biogenesis; living cells can arise only from preexisting living cells.

But the matter remained unresolved until two years later when the great French scientist Louis Pasteur, in a series of classic experiments demonstrated that (1) microorganisms are present in the air and can contaminate solutions; and (2) the air itself does not create microbes.

Pasteur filled short-necked flasks with beef broth and boiled them, leaving some opened to the air to cool and sealing others. While the sealed flasks remained free of microorganisms, the open flasks were contaminated within a few days.

In a second set of experiments, Pasteur placed broth in flasks that had open-ended, long necks. After bending the necks of the flasks into S-shaped curves that dipped downward, then swept sharply upward, he boiled the contents. The contents of these uncapped flasks remained uncontaminated even months later. Pasteur explained that the S-shaped curve allowed air to pass into the flask; however, the curved neck trapped airborne microorganisms at the bottom of the curve, preventing them from traveling into the broth.

Pasteur not only executed a brilliant set of experiments, he also used his zeal and skill as a promoter of his ideas to strike a decisive blow to spontaneous generation. For example, in a lecture at the Sorbonne in Paris in 1864, Pasteur said that he had water for his experimental liquids to generate life. But, he said, "....it is dumb, dumb since these experiments were begun several years ago; it is dumb because I have kept it sheltered from the only thing man does not know how to produce, from the germs which float in the air, from Life, for Life is a germ and a germ is Life. Never will the doctrine of spontaneous generation recover from the mortal blow of this simple experiment!" Pasteur's work not only disproved abiogenesis, but also offered support to other researchers attempting to show that some diseases were caused by microscopic life forms. Thus, in a simple, but elegant set of experiments, Pasteur not only struck the doctrine of spontaneous generation a "mortal blow," but also helped to establish the germ theory of disease .

Marc Kusinitz

Spontaneous Generation

From the seventeenth century, through the Middle Ages, and until the late nineteenth century, it was generally accepted that some organisms originated directly from nonliving matter. Such "spontaneous generation" appeared to start in decaying food, urine, and manure because worms or maggots could be seen hatching there after a few days. It was also believed that animals that lived in mud, such as frogs and salamanders, were generated by the mud in which they lived. Additionally, there were the widely held misconceptions that rats were spontaneously generated in piles of garbage or created from magical recipes. One seventeenth-century recipe even called for the creation of mice from sweaty underwear and wheat husks placed together in a jar for twenty-one days. Although such a concept may seem ludicrous today, it was congruous with other cultural and religious beliefs of the time.

Francesco Redi, an Italian physician, naturalist, and poet, first challenged the idea of spontaneous generation in 1668. At that time, it was widely held that maggots arose spontaneously in rotting meat. Redi did not believe this. He hypothesized that maggots developed from eggs laid by flies. To test his hypothesis, he set out meat in a variety of jars, some open to the air, some sealed completely, and some covered with gauze. As Redi had expected, maggots appeared only in the jars in which the flies could reach the meat and lay their eggs.

Unfortunately, many people who were told or read about these experiments did not believe the results, so if they still wanted to believe in spontaneous generation, they did. Even Redi continued to believe that it occurred under some circumstances and cited the example of grubs developing in oak trees. The invention of the microscope during this time only seemed to further fuel this belief, as microscopy revealed a whole new world of microorganisms that appeared to arise spontaneously.

The debate over spontaneous generation continued for centuries. In the mid-eighteenth century, two other well-documented experiments—one by John Needham, an English naturalist, and the other by Lazzaro Spallanzani, an Italian physiologist—were attempted but were considered by proponents of spontaneous generation to be unpersuasive.

The idea of spontaneous generation was finally laid to rest in 1859 by the French chemist, Louis Pasteur. The French Academy of Sciences sponsored a competition for the greatest experiment that could either prove or disprove spontaneous generation. Pasteur devised a winning experiment where he boiled broth in a flask, heated the neck of the flask in a flame until it became pliable, and bent it into the shape of an "S." With this configuration, air could enter the flask, but airborne microorganisms could not, they would settle by gravity in the neck of the flask. As Pasteur had expected, no microorganisms grew. However, when he tilted the flask so that airborne particles could enter, the broth rapidly became cloudy with life. Pasteur had both refuted the theory of spontaneous generation and demonstrated that microorganisms are everywhere, including the air.

see also Biological Evolution.

Stephanie A. Lanoue

Bibliography

Krebs, Robert. Scientific Development and Misconceptions Throughout the Ages. Westport, CT: Greenwood Press, 1999.

Random House Dictionary of Scientists. New York: Random House, 1997.

SPONTANEOUS GENERATION

Also referred to as abiogenesis, the theory that living things arise de novo without living parents from lifeless matter, held almost universally until mid-17th century. After careful observation of the habits of animals and the life cycles of plants, aristotle concluded that some insects arise from putrefying earth or vegetable matter, oysters from slimy mud, lice from the flesh of animals, and so on. I. Newton, W. Harvey, and R. descartes were among the eminent scientists who accepted the theory without question.

The attempt of the ancients and medievals to explain the origin of lower forms of life from natural causes, rather than attributing it directly to a supramundane or divine power, was scientifically respectable. Without microscopes, these men could see neither the minute eggs of many of the invertebrates nor the spores of plants or other reproductive structures of lower animals and plants. Their scientific frame of mind demanded that they account for the change from the inanimate to the animate by proximate or proper causes; the only alternative to this, in their way of thinking, was belief in a special creation for each organism. The medievals preferred spontaneous generation for much the same reasons that 20th-century scientists seek to explain the origin of life from concatenations of molecules in the oceans of the primitive earth.

St. thomas aquinas accepted the spontaneous generation of living things from decaying matter. He also accepted the ancients' postulate that the active principle for such a power resides in some way in a celestial body. Since the sun's heat has a beneficial effect on the growth and development of living things, he thought that such heat could communicate the power of life to the slime of the earth. Not regarding the heavenly bodies as animated, however, he held that they could produce living things only in virtue of some higher power (De pot. 6.6 ad 10).

In Aquinas's terminology, the sun, not being determined to produce any one kind of animal or plant, is referred to as a universal cause (Summa theologiae 1a, 115.3 ad 3). The species of animals produced by such a cause are determined by the proportionate composition of elements in the decaying organic matter (ibid. 1a2ae, 60.1).

The forms of such organisms are not in the sun, any more than the forms of new animals or plants are in the gametes that give rise to them (ibid. 1a, 118.1 ad 4). Rather they are educed from the potency of matter, just as the form of water can be said to be educed from the potentiality of hydrogen and oxygen (see matter and form).

To avoid a disproportion between cause and effect, St. Thomas argued that just as a living canine parent must empower the seed or gamete to produce another dog, so some living being must empower a celestial body to bring forth life. In his analysis, angels could fulfill this function, since they have more knowledge of, and greater power over, celestial and terrestrial operations than man (De pot. 3.11 ad 13; 6.3). In light of man's rapidly increasing control over matter and energy, it would be in accord with such an analysis to hold that man might be able to dispose matter in such a way as to educe from it a living form. The living thing produced would then be the result of nature as well as of man's art (cf Summa theologiae. 3a, 75.6 ad 1).

See Also: life.

Bibliography: r. f. nigrelli, ed., "Modern Ideas on Spontaneous Generation," Annals of the New York Academy of Sciences 69 (1957) 257–376. j. b. conant et al., eds., Harvard Case Histories in Experimental Science, 2 v. (Cambridge, MA 1957) v. 2.

[a. m. hofstetter]

spontaneous generation The discredited belief that living organisms can somehow be produced by nonliving matter. For example, it was once thought that microorganisms arose by the process of decay and even that vermin spontaneously developed from household rubbish. Controlled experiments using sterilized media by Pasteur and others finally disproved these notions. Compare biogenesis. See also biopoiesis.