Since the turn of the
20th century, the scientific community has widely rejected directed
evolution, a theory mostly associated with the name of Jean-Baptiste
Lamarck (1774-1829).Disapproval of Lamarck's Theory of Inheritance of
Acquired Characteristics has not dissuaded investigators
from attempting to prove that the grand old man of evolution may have been
right after all. If they can do that, then the concept of humanity
battling against a harsh world will be reconsidered. Evolution will
graduate from a theoretical study to a practical philosophy that guides
Note: The words
directed evolution, Inheritance of Acquired Characteristics, Lamarckian
evolution, and adaptive mutations are expressions that have
slightly different meanings to different persons. For this article the
words will be used interchangeably and will have the same context.
Lamarck is considered the
more complete theorist of the early promoters of the Theory of Evolution
that Charles Darwin later adopted and greatly expanded. Lamarck followed
contemporaries in explaining evolution as a directed process and
self-adapting means by which species changed their characteristics in
response to environmental changes and passed the characteristics to future
populations. Darwin published his Principle of Natural Selection on
November 24, 1859, at the same time as did co-discoverer Alfred Russel
Wallace. In Charles Darwin's words:
(from mutations) useful to any
organic being ever do occur, assuredly individuals thus characterized
will have the best chance of being preserved in the struggle for life;
and from the strong principle of inheritance, these will tend to produce
offspring similarly characterized. This principle of preservation, or
the survival of the fittest, I have called Natural Selection.
Through the remainder
of the 19th century, academics of the two evolution theories competed with
one another for scientific approval. Contemporary religious authorities
considered them both as acadenic aberrations.
The Losing Battle of Lamarck's
Darwin's Theory of
Natural Selection obtained greater scientific recognition, but Lamarck's
concepts had support. German Zoologist August Weismann, while performing
experiments in the late1880's to prove Lamarck right, convinced himself
that Lamarck had been wrong.
that the cells in mammals that determine heredity (germline)
became isolated before birth from the cells (soma) that
determine the growth of the mammal. No mechanism had been determined by
which changes in the soma could affect the germline,
or by which soma changes could be inherited. This
phenomenal discovery, still known as Weissman's barrier,
should have ended the discussion. However,in some animals and plants, the
separation between germline and soma occur
after birth. Those cases contain a possibility of inheritance of
acquired characteristics. Weissman's conclusions only made
Lamarck's supporters more eager to prove Lamarck's theories by
experimentation. One of the attempts had tragic consequences.
Paul Kammer claimed to have living proof that toads (Alytes), which
normally mate on land, developed calloused pads in order to hold slippery
mates when they became seduced to mate in water.The land toads developed
pads developed after only a few generations. Charges of investigative
fraud countered Kammer's claims. Paul Kammer committed suicide six months
after the charges appeared and his suicide seemed to confirm the charges.
The hostility of the scientific community to Lamarck's supporters, and
Kammer's suicide that resulted from this hostility, diminished the ardor
of Lamarck's adherents, but not in the Soviet Union.
Russian plant breeder
T.D. Lysenko attemped to improve plant yields by inducing "environmental"
changes during plant germination with use of a process known as
vernalization. Lysenko's work is still controversial. If he had some
success, it became buried in the Cold War rhetoric. Having his theories
championed by a leading scientist of the Soviet Union further deteriorated
Lamarck's image in the West. Lamarckians graduated to Neo-Lamarckians.
challenge to Darwin's Theory of Natural Selection hinged on whether
mutations were directed or random. Without complete knowledge of the
origin of mutations, neither evolutionary theory could claim complete
legitimacy. In 1943, Salvador Luria and Max Delbruk showed that cultures
of bacteria grown in laboratory dishes, and which survived lethal doses by
a selective agent, obeyed the theory of random mutation--the distribution
of the surviving microbes could only have occurred if the bacteria had
mutated before presentation of the lethal agent. The statistical
distribution of survival indicated that post lethal dose mutations had not
occurred. This final blow to Lamarck's concepts still did not permanently
deter Lamarck's followers. It encouraged them to examine Luria's tests and
devise new ones - and for good reasons--Natural Selection had not
answered all the problems of the theory and Lamarck's theory had positive
social implications that contrasted with the negative impact of Darwin's
The Problems with
Luria's and Delbruk's
successful investigations removed one doubt from the Theory of Natural
Selection--that random mutations could improve a species chance of
survival. The Darwinians had no more doubts in their beliefs. Over the
years, a lesser recognized group of evolutionists demanded answers to
(1) Why haven't the
fossil remains displayed intermediary stages of growth expected from the
gradual changes of Natural Selection?
(2) How can the unpredictable nature of random mutations provide a
suitable mechanism for the development of complex systems such as the
nervous system, eye and armed weapons in animals, such as sprays?
(3) Do a sufficient number of generations exist to adapt to the slow
changes predicted by random mutations and evolve to the human species as
it exists today?
(4) Does a slight superiority of a positive, but still not obvious benefit
of a particular mutation, mean that mating will proceed quickly enough to
capture the benefits of the mutation? Can't it more easily lag into
Darwin realized some
of these limitations to his theory. He addressed them with care, but not
with final authority. Other evolutionists have shown that nervous system
and eye developments have a variety of intermediate patterns in the animal
world and a gradual evolution of these systems is entirely possible.
Neo-Darwinist Stephan Jay Gould, who did not have total acceptance from
other neo-Darwinists, proposed a Theory of Punctured
Equilibrium--evolutionary changes occur in short and quick bursts. Using
this theory, the lack of fossil records and incomplete number of
generations become lesser limitations to Darwin's theory. Some
evolutionists still felt their questions had not been satisfactorily
answered and must be eventually explained. The perception that limitations
remained in the Theory of Natural Selection prompted these
evolutionist to find a more complete scientific theory of evolution. Their
more complete theory did not attempt to contradict Natural Selection.
It attempted to complement it and strengthen its acceptance.
Elegance of Directed Evolution
was not the only reason driving the Neo-Lamarckians. Directed evolution
pleases social reformers. Natural Selection angers them.
- Darwin speaks of competition.
Lamarck speaks of cooperation.
- Darwin represents survival of
the fittest. Lamarck speaks of the species making itself fit.
- Natural selection
makes humankind a pawn of random mutations that indirectly determine
its fate. Inheritance of acquired characteristics has humankind
more directly involved in its fate.
- Natural Selection
is harsh, cruel and insensitive. Inheritance of acquired
characteristics is optimistic, soothing and sensitive.
- Natural Selection
has not shown practical applications. Inheritance of acquired
characteristics promises practical applications that can benefit
- Random mutations
can be lethal. Adaptive mutations are not lethal.
The Attempted Proofs of Directed
Many experiments have
been performed with to prove directed evolution. Only a few of them will
be mentioned, and most of them have their critics and alternative
inheritance systems, in which the phenotype (observed appearance of an
organism) that expresses cell information is modified by environmental
stress, have been noticed as modified phenotypes appearing in subsequent
In 1988, a team of
Harvard biologists under the leadership of Joseph Cairns
challenged the previous experiments
performed by Luria and Delbruck in 1943. The early experiments seemed to
prove that all mutations occurred randomly and none could be
directed. Cairns group reasoned that in the earlier investigations the
bacteria had been given too lethal a dose. They died before they could
develop and propagate self-directed mutations.
experimenters used bacteria that could not grow in a specific environment
because they lacked a working gene for an enzyme needed to metabolize the
only available food. By genetic engineering, the bacteria were given
versions of the necessary gene in which the coded message was, in effect,
scrambled and therefore useless. Most, if not all, the bacteria failed to
grow. After a few days they began thriving, feeding and reproducing.
The distribution of bacteria colonies that survived showed that many
bacteria had unscrambled the code and performed self-directed mutations
that corrected the deficiency.
Barry G. Hall, an
evolutionary biologist at the University of Rochester, NY,
damaged cell DNA by two different forms of genetic damage. Mutations that
might occur to repair either of the damages were not sufficient to benefit
the cell. Both damages required repair for any benefit.
In one of two
1991 experiments, which are too complicated and lengthy to describe in
this space, he showed that the cells repaired themselves by producing the
correct mutations at a rate billions of time sooner than if chance alone
had caused the changes. (Washington Post, April 20, 1992, p.A3)
Both of these investigations were
criticized as lacking effective controls, and ascribed to known
physiological processes. Subsequent work by Hall with more controlled
experiments eventually led to experimentally verified acceptance.
(Johannes Wirz, Progress towards complementarity in genetics, Elemente der
Naturwissenschaft, 64(1), 37-52 1996)
changes, which are alterations in gene expression, can be passed from
mother cells to daughter cells.
However, it had not been shown that subsequent generations inherited the
same properties. Evidence is accumulating that the epigenetic changes
are not erased. This phenomenon has been observed in plants, fruits
and yeast. (Was Lamarck just a little right? Michael Balter, Science,
April 7, 2000)
Geneticist Enrico Coen and others at the John Innes Centre in Norwich,
U.K. reported that a mutant version of the toadflax plant (flowers
radial rather than bilateral) was due to an epimutation in which a gene
was not expressed. The gene state and and the flower characteristic were
inherited by subsequent generations of toadflax plants. (Nature,
September 9, 1999)
epigenetic changes have also been observed in mammals.
Mohan Raizada at
the University of Florida in Gainesville, Florida and others
inserted a therapeutic gene into a
modified virus, and delivered the gene into the hearts of rats that are
predisposed to high blood pressure. These rats and two subsequent
generations were protected from hypertension.
"Our data support the notion
that the AT1R-AS is integrated into the parental genome and is transmitted
to the offspring. The proposed germ-line transmission of the AT1R-AS is
consistent with previous reports demonstrating the integration of
retroviral vector and its germ-line transmission in other systems."
Cardiovascular Protection From Hypertension by the AT1 Receptor Antisense
Gene Therapy in Hypertensive Rat Offspring, Circulation Research.
Jablonka and Biologist Marion J. Lamb
present a detailed study of
'epigenetic inheritance' and multiple inheritance systems in their
book: Epigenetic Inheritance and Evolution--The
Lamarckian Dimension. On P.
26 they state:
In recent years,
molecular biology has shown that the genome is far more fluid and
responsive to the environment than previously supposed. It has also
shown that information can be transmitted to descendants in ways other
than through the base sequence of DNA.
On Page 27, they
The nature of
different types of heritable variation is now beginning to receive
closer attention, and there is a growing realization not only that some
DNA variations can be environmentally induced, but also that there are
non-DNA heritable variations that play a crucial part in development.
Until now, no mechanism
for inheritance of acquired characteristics has been demonstrated
in vertebrates. Nevertheless, means for acquired characteristics to cross
Weismann's barrier have been theorized and presented. Molecular
biologists Edward J. Steele, Robyn A. Lindley and Robert V. Blanden,
who work at different Australian research centers, have been active for
many years in investigating the immune system's adaptive processes and
have tried to apply a similar analogy to an inheritance of acquired
characteristics. On P. 166 of their book titled: Lamarck's
Signature, they present one scheme:
Selection Theory' predicts the germline transmission of acquired somatic
mutations of antibody V-region genes. It could be affected via the
agency of the enzyme reverse transcriptase (copying RNA into DNA) plus
the ubiquitous, naturally occurring endogenous RNA retroviruses
(produced by lymphocytes) acting as 'gene shuttles' ferrying mutated
V-region gene sequences into germ cells. This would then be followed by
the physical integration of this somatically derived genetic information
into the germline DNA so as to replace a pre-existing gene sequence.
of Lamarckian Evolution
The gradual changes that
occur from random mutations in individuals of a species dictate that
Natural Selection has abrupt but slow evolutionary changes. Lamarck's
hypothesis predicts that characteristics change in large populations and
therefore have a more rapid evolution. Recent studies have concluded that
evolutionary changes can be quick.
- According to Megan Higgie and
colleagues at the University of Queensland, Australia,
a type of male fruit fly altered within just nine generations the
chemical signals it puts out to attract females in its species.
- Andrew P. Hendry and colleagues
at the University of Massachusetts,
learned that just after only 13 generations, sockeye salmon developed
distinctly different sizes depending on whether they spawned in a river
- Ruth Shaw, University of
Minnesota, and University of California researchers, David N. Reznick
and F.H. Rodd captured
guppies from two downstream pools and placed them in pools upstream of
waterfalls. In the downstream pools the guppies had been plagued by
large predators but in the upstream pools, only small predators were
around. After four years, these guppies began reaching maturity. They
quickly adapted to their new and less threatening surroundings by
growing larger and by producing fewer offspring.
Summarizes Lamarck's Contributions
C.H. Waddington, a reknowned
evolutionist, provided an answer to the environment's influence on the
evolution path by tracing his development as an evolutionist in his book:
The Evolution of an Evolutionist.
Although he worked during the decades of
the 50's and 60's, and before current thoughts and experiments, his words
still have meaning today.
Early in his career,
he praised Lamarck. On P.38:
theories had, of course, been put forward some time before Darwin wrote
Origin of Species. The most famous of these earlier discussions is that
associated with the name of Lamarck. It has suffered a most surprising
fate. Lamarck is the only major figure in the history of biology whose
name has become to all extents and purposes, a term of abuse. Most
scientists' contributions are fated to be outgrown, but very few authors
have written works which, two centuries later, are still rejected with
an indignation so intense that the skeptic may suspect something akin to
an uneasy conscience. In point of fact, Lamarck has, I think, been
somewhat unfairly judged.
that evolution should consider an adaption process that is influenced by
the environment. On P. 24
modern view is that, in nature, the direction of mutational change is
entirely at random, and that adaptation results solely from the natural
selection of mutations which happen to give rise to individuals with
suitable characteristics. I want to argue that this theory is an
extremist one, and that, in essaying to account for adaptation, it
neglects to call to its aid the doctrines emerging in other fields of
In a later article
Waddington explained the doctrines of modern biology that perform the
adaptation process. He termed the process genetic assimilation and
relied on natural selection for transferring the adaptation to future
generations. On P. 91:
The process of
genetic assimilation is one by which a phenotypic character, which
initially is produced only in response to some environment influence,
becomes, through a process of selection, taken over by the
genotype, so that it is formed even in the absence of the environmental
influence which had at first been necessary.
assimilation is brought about by the operation of orthodox genetic and
embryological principles. It depends on two main types of fact: (a) that
the capacity of an organism to be modified in response to an
environmental stress is under genetic control and can be altered by
selection; and (b) that development processes exhibit a balance between
tendencies to be modified by the environment and tendencies to resist
Evolution is Today
evolution could be proven, then its knowledge and acceptance would
greatly affect all mankind.
Inducing agents might
be used to direct the immune system to rapidly develop permanent antibody
solutions to diseases and carry these solutions to subsequent populations.
Genetic engineering would include Lamarck's concepts, giving it a more
positive approach and making it more aware of treacherous and possible
damaging effects. Agriculture could take advantage of environmental
manipulation of plant life. The latter investigation has already been
explored in the Soviet Union with varying and controversial success.
intensive investigations of Lamarck's theories and claims made from them,
Lamarck's Inheritance of Acquired Characteristics has only mildly
interested the scientific community.
One reason is that all of Natural
Selection has been widely accepted and its dogmas have become an
integral part of the academic community. The leaders of laboratories,
institutions and universities have a clear interest in maintaining a
status quo in evolutionary thinking. But that isn't the major reason.
The major reason is
that Lamarck's followers have investigated for decades and have not found
a 'Killer App', a revelation that will totally excite rather than
mildly interest the scientific community. They have not located 'the
smoking gun' that sufficiently derails the intensive preoccupation
with Natural Selection and permits an intensive examination of a
complementary approach to evolution. Proponents of Natural Selection
note that environment might influence the genes, but maintain that
Natural Selection determines the appearance of acquired
characteristics in future generations.
Lamarck's hypothesis of Inheritance of Acquired Characteristics has
one additional implication: If humankind is able to respond to the
environment and direct its evolution, then the questions concerning
Natural Selection will be answered. The intervention of a higher
authority in the evolutionary process will become superfluous. The last
nail in the coffin of creationism will be hammered.
How Retrogenes are Changing
Darwin's Natural Selection Paradigm, Edward J. Steele, Robyn A. Lindley,
Robert V. Blanden, Perseus Books, 1998.
Inheritance and Evolution--The
Lamarckian Dimension, Eva Jablonka and Marion J. Lamb, Oxford University
The Evolution of an
Waddington, Cornell University Press, 1975.