The Role of Experiments,
Preconceived Ideas, and Scientific
Authorities in Early Controversies
about the Origin of Life and the
Creation of Artificial Life in the
Laboratory
Ute Deichmann
Jacques Loeb Centre for the History and Philosophy
of the Life Sciences, Ben-Gurion University of the
Negev, Israel
1923
1936
• The question of the origin(s) of life has
occupied scholars and scientists since
ancient times.
• For centuries, it had been dominated by
the general belief in the spontaneous
generation of various forms of life.
Outline:
1. Origin of life through spontaneous
generation; the examples of
evolutionary biology and cell biology
2. Experiments and preconceived ideas –
reviewing the controversies on Pasteur
3. From spontaneous generation to the
creation of artificial life
1.Origin of life through spontaneous
generation; the examples of
evolutionary biology and cell biology
Spontaneous generation:
Doctrine that organisms, such as insects, worms,
mice, microorganisms, arise from non-living
sources, e.g. mud, putrifying animal or vegetable
matter
• Aristotle (384-322 BCE)
• The early Church Fathers (ca. 300-400 CE)
• Doctrine was finally
abandoned in early 20th century
First major blow to this doctrine regarding larger
anmals by Francesco Redi (1668):
• Flies are only found in the samples exposed to the air,
not in those protected from the air.
• Conclusion: They do not arise spontaneously, but only
from eggs (observed under the microscope)
Extensive discussions on the origin of life in
the 19th century
Concerned with
• the supposed formation of infusoria and microorganisms from particles of organic matter
• cell theory
Spontaneous generation and theory of evolution:
Lamarck: Philosophie Zoologique 1802:
Nature is producing species of animals in a
progressive way, beginning with the most imperfect
or simple and ending with the most perfect that is the
most complex one.
But the more primitive forms of life did not disappear.
Solution: Spontaneous generation
Spontaneous generation and theory of evolution:
• Oken 1805: proposed his idea of an “Urschleim”, from
which primitive forms of life were generated. Was later
taken up by...
• Haeckel: integrated it into his theory of “Monera”.
Primitive living beings which supposedly consisted only
of a small homogeneous mass of protoplasm and built
the basis of life. Protistologists: All “Monera“ forms
contain single or multiple nuclei. Concept was
abandoned.
• Darwin accepted possibility of spontaneous generation
through the 1870s. Remained ambivalent thereafter,
trying to avoid this question.
Spontaneous generation and cell theory:
Schleiden, Schwann 1838: Theory for the
generation of cells as structural elements of
organisms and for their role in the development of
form.
Concept of de novo formation of cells by
crystallizing out from a continuous and formless
matrix.
• Schleiden hoped that “that natural science may
be able one day to regard the cell as the
necessary form of a normal condition of a
permeable (assimilated organic) substance, just
as the crystal is a necessary form of the
inorganic substance. Then would all individual
and simple cells originating and existing in
organisms be but a definite organic
crystallization.”
• Schwann believed that “organisms are nothing
but the form under which substances capable of
imbibition crystallize.”
Schwann’s and Schleiden’s predilection with the cell’s
de novo generation and crystallization
• Fitted the ideas of the spontaneous generation of
micro-organisms and that of neoplasms as new
formations of tumours
• May be related to their strong adherence to Kantian
and Friesian philosophy of the unity of nature,
• Might have been influenced by the romantic school
of natural philosophers (e.g. Lorenz Oken),
• Obscured the “fundamental significance” of cell
theory (E.B. Wilson,1928)
An early critic:
• Robert Remak
– Rejected Schwann’s theory of de novo cell
formation from the beginning,
– Rejected Virchow’s et al.’s theory of the
new formation of neoplasms of tumours.
“The origin of cells de novo is no more credible
than the spontaneous generation of life” (1852).
1850 -1900:
• The notion of cells from crystallisation was replaced
by the notion of cells from the division of preexisting cells. (Remak 1852, Virchow 1855: Omnis
cellula e cellula)
• The doctrine of spontaneous generation continued
to be upheld by many in regard to micro-organisms.
2. Experiments and
preconceived ideas – reviewing
controversies on Pasteur
• Experiments of Pasteur in 1861 are
considered crucial by many for the final
abandonment of the doctrine of
spontaneous generation.
Pasteur: "On the organized bodies which exist in the
air: Examination of the doctrine of spontaneous
generation" (1861):
• Micro-organisms do not
generate in a boiled
bouillon as long as dust
was prevented from
entering it. Dust carries
micro-organisms.
• Micro-organisms, too, do
not arise from inanimate
matter but only from
existing ones of the same
kind.
Some historians’ assessments:
• Pasteur allowed his research to be guided by his
preconceived idea and ideological bias against
spontaneous generation (e.g. Farley 1978, Geison 1995).
• Background: The debate on spontaneous
generation in 19th century France was related to a
larger debate about a materialistic and religious
way of life.
– Spontaneous generation was embraced by anti-religious
scholars, because it rendered life a merely physical
process based on chance events.
• As a member of the French cultural establishment
Pasteur resented these materialistic views.
My comments:
Pasteur had
not only
• ideological reasons for disliking spontaneous
generation.
but also
• scientific reasons for disliking it: Wide
knowledge on fermentation and micro-organisms
(e.g. their constancy and specificity)
► conviction that a spontaneous generation of
micro-organisms was highly unlikely.
• Pasteur’s experiments were conducted with a
preconceived idea.
• This did not render his experiments questionable,
because they were accompanied by wide knowledge,
logical designing of the experiment and skills.
• His opponents, too, had preconceived ideas, but often
lacked his other attributes.
• Experiments alone were not able to disprove
spontaneous generation.
• Increasing knowledge in micro-biology and
biochemistry together with logical reasoning and clear
experimentation led to the final abandoning of
spontaneous generation.
• The abandonment of the ideas of spontaneous
generation of life and cells was a pre-requisite
for scientific research into the artificial creation
of life in the laboratory.
• The question of the origin of life became
related to that of the artificial generation of life
in the laboratory.
3. From spontaneous generation
to the creation of artificial life
A. The primacy of form and growth in the
morphological-colloidal-mathematical
approach (early 20th century)
Around 1900:
Scientists tried to mimic features of life, especially
growth and form on the basis of osmotic growth
and the colloidal concept of nature.
1864 Moritz Traube:
First scientific study of artificial semi-permeable
membranes and first experiment-based
physicochemical theory of cell growth; mimicked
the growth of plant forms.
French physicist Stéphane Leduc:
• “Traube made the first artificial cell, ... This
remarkable research should have been the
starting-point of synthetic biology.” (1911)
• 1912 La Biologie Synthétique
Leduc, La Biologie Synthétique, 1912
Fig 32. - Croissance
osmotique de chlorure et
nitrate de manganèse
avec capsules terminales
présentant un haut degré
d'organisation.
Leduc 1912:
– Transformation of substances leads to an increase
of osmotic pressure in the tissues: “transformation
of chemical energy into osmotic energy”.
– No clear boundary between “life and physical
phenomena”.
– Virchow’s “toute cellule vient d'une cellule” is an
error of reasoning; cells can be created differently.
Leduc promoted an entirely morphological-physical
concept of life and neglected novel concepts (e.g.
individuality of chromosomes; specificity of enzyme
reactions).
B. The specificity of basic structures and
processes in the molecular approach (early
20th century)
The notion of the relevance of specific molecules for an
understanding of basic features of life preceded
macromolecular chemistry.
German American physiologist Jacques Loeb:
“The living cell synthesizes its own complicated specific
material from indifferent or non-specific simple
compounds of the surrounding medium, while the crystal
simply adds the molecules found in its supersaturated
solution.
This synthetic power of transforming small ‘building
stones’ into the complicated compounds specific for
each organism is the ‘secret of life’ or rather one of
the secrets of life.” (Loeb 1916)
Loeb rejected claims of the synthesis of life through
osmosis:
"The fact that the living cell grows after taking up food
has given rise to curious misunderstandings. Traube has
shown that drops of a liquid surrounded with a
semipermeable membrane may increase in volume
when put into a solution of lower osmotic pressure. This
has led, and is possibly still leading, to the statement that
the process of growth by a living cell has been imitated
artificially. Only one feature has been imitated, the
increase in volume; but the essential feature of the
process in the living cell, i.e. the formation of the
specific constituents of the living cell from nonspecific products, has of course not been imitated."
(Loeb 1916)
Loeb held that the artificial creation of life was not
only a physical process, but had to involve the
synthesis of specific molecules, in particular selfreplicating DNA (“nuclear material”).
“Nobody has thus far succeeded in this, although
nothing warrants us in taking it for granted that this
task is beyond the power of science.” (Loeb 1909)
• Similar contrasting themes (Holton) or
basic beliefs (Polanyi) were prevalent in
subsequent stages of research on the
origin of life and creation of artificial life:
• Predilection for the
concept of unity in nature
• Descriptive, mathematical,
colloidal approaches
• Emphasis on physical
concepts of life, e.g.
growth and form
• Predilection for the
distinction between living
and non-living nature
• Mechanistic experimental
approaches
• Emphasis on chemical
concepts of specificity of
structures and molecules
----------------------------------
------------------------------------
• Crystallization of cells
from unspecific fluids
• Synthesis of life by
osmotic growth
• Schleiden, Pouchet,
Haeckel, Leduc,
Thompson
• Cells only from existing
cells of the same type
• Synthesis of life by
synthesis of specific
macromolecules
• Remak, Pasteur, Loeb,
Wilson,
The different approaches have not been
equally successful.
• In 2010, around 100 years after Loeb’s
prediction, a completely chemically
synthesized DNA, which was fully functioning,
was successfully transferred into a bacterial
host cell by Craig Venter and his team.
Science. 2010 July 2
Creation of a bacterial cell controlled by a
chemically synthesized genome.
•
Gibson DG, Glass JI, Lartigue C, Noskov VN, Chuang RY, Algire MA,
Benders GA, Montague MG, Ma L, Moodie MM, Merryman C, Vashee S,
Krishnakumar R, Assad-Garcia N, Andrews-Pfannkoch C, Denisova EA,
Young L, Qi ZQ, Segall-Shapiro TH, Calvey CH, Parmar PP, Hutchison CA
3rd, Smith HO, Venter JC
Outlook:
Research in modern synthetic biology can
be fruitful for solving basic questions on
evolutionary biology and the origin of life.
Questions
• When will it be possible to synthesize a
whole organism?
• Will this be the same life as that which has
evolved for 3-5 billions of years?
THANK YOU!