Origin of life and ‘spontaneous generation’.
At some point we all ask "Where do we come from?"
For millennia, the Origin of Life was thought to be the result of Abiogenesis (also
known as "Spontaneous Generation"). The doctrine of Spontaneous Generation holds that
organic life could and does arise from inorganic matter. As late as the 17th century, there
were recipes to "create" life. Take sweaty rags, wrap them around wheat, and set them in
an open jar. In 21 days, you'll "create" mice. For rats, just throw garbage in the street. In a
few days, rats will take the place of the garbage. All over the world, in Europe, Asia,
Africa and the Americas, mankind was formulating recipes for "creating" bees, lice,
scorpions, maggots, worms, frogs, etc. Even the greatest minds of the ancient world held
this view. Aristotle believed this, as he had to, for he saw evidence with his own eyes.
In the 1660’s an Italian doctor named Francesco Redi attempted to disprove the
idea of spontaneous generation. It was a commonly held belief in Redi’s time that
maggots came from meat. Redi had made careful observations of maggots and noticed
over the course of 20 days, the maggots developed into flies. Redi then believed that the
maggots that were commonly found on meat were the result of flies landing on the meat,
and not the result of the meat spontaneously turning into flies. Redi decided to test this
idea. He placed meat into open jars so that flies could reach the meat. He also placed
meat into jars which he sealed tightly. Maggots only appeared in the open jars. Redi
repeated this experiment many times, with many types of meat, and in each instance the
result was the same. His results were clear and his hypothesis was deemed correct.
However, his arguments were muted by the Dutch janitor Anton van
Leeuwenhoek. Leeuwenhoek’s hobby was grinding small lenses and he perfected the
microscopes. He looked at everything he could, from hair to blood. In 1675 he
discovered living things in ditch water. He called them ‘animalcules’, what we now call
protozoa from the greek “first animals”. He discovered that yeast was composed of tiny
living things even smaller than protozoa and in 1683 observed still tinier living things,
which we now call bacteri, from the greek “little rod”. Van Leeuwenhoek made a broth
from water and peppers, and found that protozoa appeared. His observations ‘proved’ to
some that 'spontaneous generation' occurred in a cooked and filtered broth, although
whether he supported this idea is not clear. He made other observations that opposed the
prevalent theory of spontaneous generation and demonstrated that granary weevils, fleas,
and mussels are not created from wheat grains and sand but develop from tiny eggs. He
described the life cycle of ants, showing how the larvae and pupae originate from eggs.
Leeuwenhoek also observed plant and muscle tissue, and described three types of
bacteria: bacilli, cocci, and spirilla. Interestingly, he kept the craft of making his lenses a
secret, however, so that not until the improvement of the compound microscope in the
19th century was the next observation of bacteria made.
The English Roman Catholic Priest John Needham conducted similar experiments
to Van Leeuwenhoek, but sealed the vessels after placing the broth inside. . He boiled 2
flasks full of meat broth for several minutes. He believed that boiling the meat broth
killed all of the microorganisms. He then put a cork in one flask to prevent air from
entering the flask, and left the other flask open. A short time later both flasks had
become cloudy, indicating that they both had microorganisms in them, proving that
spontaneous generation existed. The concept of spontaneous generation was intact until
the next blow almost 100 years later.
In 1767 Lazzaro Spallanzani ((1729-99), Italian physiologist, who was one of the
founders of experimental biology. He was educated in law at the University of Bologna,
later becoming a professor in physics. Spallanzani conducted many experiments. He
investigated the ability of many lower animals to regenerate parts, and in a transplant
experiment he successfully grafted the head of one snail onto the body of another. He
studied the circulation of blood through the lungs and experimented on digestive juices,
which, he observed, were specialized for digesting different foods. Attempting to
discover what part of the semen was essential for generation, he filtered samples from
amphibians and discovered that the higher the filtration, the less likely was the
development of an egg. His most famous experiment shattered Needham’s work and
forged new evidence against spontaneous generation. Instead of using corks, which he
viewed as porous, he conducted an experiment where he boiled broth and then fused the
glass of the neck. He also believed that Needham had failed to thoroughly sterilize his
flasks. Spallanzani boiled his flasks for a full hour, and found that no life would occur
until the flasks were opened to air. Needham also replicated the work of Needham and
found that if the flasks were not fully sterilized and fully sealed bacterial life would
eventually develop.
The spontaneous generationists developed a new argument against Spallanzani.
They said that the heat killed the ‘vital principle’ that was necessary for life to
spontaneously generate. Without the VP, it was impossible for life to generate.
Louis Pasteur finally put spontaneous generation to rest. Born in Dole in 1822,
son of a tanner, he earned a doctorate from Ecole Normale de Paris in 1847 in chemistry
and physics. In 1854 he moved to Lille as professor of chemistry , and dean of science.
He worked on fermentation, showing that yeast was necessary for wine production, but
that sterilization kept the wine (or beer) from souring. He, of course, extended his work
to milk, hence ‘pasturization’. He worked on silkworms, discovering a bacterial parasite,
and through controlled breeding, saved the industry. He came up with the germ theory,
although many ridiculed it as saying that something so small couldn’t be that harmful. Tt
top it all off he also came up with the first vaccines for anthrax and rabies.
In 1885, a young boy and his mother arrived at Pasteur’s laboratory; the boy
had been bitten badly by a rabid dog, and Pasteur was urged to treat him with his new
method. At the end of the treatment, which lasted ten days, the boy was being inoculated
with the most potent rabies virus known; he recovered and remained healthy. Since that
time, thousands of people have been saved from rabies by this treatment.
Pasteur’s research on rabies resulted, in 1888, in the founding of a special
institute in Paris for the treatment of the disease. This became known as the Institut
Pasteur, and it was directed by Pasteur himself until he died. (The institute still flourishes
and is one of the most important centers in the world for the study of infectious diseases
and other subjects related to microorganisms, including molecular genetics.
Fully aware of the presence of microorganisms in nature, Pasteur undertook several
experiments designed to address the question of where these “germs” came from. Were
they spontaneously produced in substances themselves, or were they introduced into
substances from the environment? Pasteur concluded that the latter was always the case.
He conducted experiments similar to Spallanzani, but left the neck open, adding a
convoluted, S shaped opening. No spontaneous generation. His findings resulted, for the
most part in the end of the debate on spontaneous generation.