Lamarckism and Neo-Lamarckism
I) Lamarckism (Lamarck’s Theory of Evolution)
Early in the 19th century, French
biologist Jean-Baptiste Lamarck put forth what is now known as Lamarckism, one
of the earliest ideas of evolution. Charles Darwin's theory of natural
selection, which finally came to be the generally accepted explanation for the
mechanism of evolution, differs greatly from Lamarck's theory of evolution.
Lamarck's idea consisted of three primary parts:
1) The Inheritance of Acquired Characteristics
Postulate: Lamarck proposed that
modifications an organism undergoes throughout its existence are transmitted to
its progeny, either via the use or abuse of bodily parts or environmental
influences.
Example: Lamarck provided an example
in the form of the giraffe's longer neck. According to his theory, giraffes
originally had short necks, but as they evolved to reach higher leaves on
trees, their necks became longer and longer, a trait that was carried down to
the following generation.
2) The Usage and Disuse Law
Postulate: According to Lamarck, an
organ that is regularly used by an organism would become stronger and more
developed, whereas an organ that is not used will eventually degenerate and
vanish.
Example: For instance, he proposed
that ostriches ceased using their wings for flight and began utilising their
legs for running, which caused the ostriches' wings to shrink and lose some of
their functionality. This disuse of wings led to a reduction in wing
size in successive generations.
3) Progression Toward Complexity
Postulate: According to Lamarck,
evolution is the flow from simple to complex forms. He proposed that over
generations, organisms constantly aim to become more sophisticated and ideal.
Example: Lamarck, for instance,
postulated that throughout time, simpler, lower species might develop into more
sophisticated, higher organisms. He believed that simple aquatic species may
evolve into more sophisticated land-dwelling organisms if given enough time.
It's crucial to remember that
Lamarck's hypothesis has been widely abandoned because it is not supported by
current genetics or the theory of natural selection, and it lacks a strong
scientific basis.
Drawbacks of Lamarckism
Lamarckism has been widely dismissed
in modern biology due to a number of serious flaws and limits. The following
are some of Lamarckism's main drawbacks:
1) Lack of Mechanism
The inability to provide a convincing mechanism for explaining how acquired features are handed down to the following generation is one of the main problems with Lamarckism. Lamarck was ignorant of genetics, which is now recognised as the basis of heredity.
2) Modern Genetics Contradicts Lamarck's idea
The way we currently understand
genetics contradicts Lamarck's idea. As we now know, the inheritance of
features gained throughout an organism's existence, such as modifications to
its body structure, is not usually carried on to progeny in the manner
suggested by Lamarck.
3) Lack of Fossil Evidence
According to palaeontologists,
Lamarckism is unable to explain the patterns found in the fossil record or the
way that complexity and adaptations have gradually accumulated over time.
Charles Darwin's idea of natural selection is more in line with the fossil
record.
4) Lack of Evidence for the Inheritance of
Acquired Characteristics
The assumption that acquired features
can be inherited is not supported by empirical evidence. Studies and
observations have not been able to prove that traits picked up during a
person's lifespan are inherited.
5) No Explanation for Extinction
Lamarckism is unable to provide a
meaningful cause for extinction-related phenomena. On the other hand,
extinctions can be explained by the idea of natural selection by elements like
competition and environmental change.
6) No Explanation for Variability
Lamarck's theory falls short in
explaining the considerable variation that has been seen within populations,
despite the fact that this is a basic idea in evolutionary biology. A more
plausible explanation for the genesis and persistence of this variability is
natural selection.
7) Rejected in Favour of Natural Selection
Around the same time as Lamarck's
theories, Charles Darwin's theory of natural selection was developed. It
offered a more thorough and fact-based explanation for the diversity and
adaption of species. As a result, the idea of natural selection essentially
took the place of Lamarckism in the scientific world.
II) Neo-Lamarckism
A more modern and altered form of
Lamarck's original theory of evolution is known as Neo-Lamarckism. The central
premise of the inheritance of acquired qualities is retained, but certain
contemporary scientific ideas are incorporated. According to Neo-Lamarckism,
there are ways besides traditional genetics for how some acquired traits can be
passed down to the following generation. Although neo-Lamarckian theory is not
commonly recognised in mainstream biology, some scientists have investigated
and studied it.
The following are some instances of
neo-Lamarckian ideas and fields of study:
1) Epigenetics
The study of epigenetics, which
examines how environmental influences can alter DNA and alter gene expression,
is frequently incorporated into Neo-Lamarckism. Children may inherit these
epigenetic modifications. For instance, research has demonstrated that environmental
elements like stress and food can lead to in epigenetic changes that may be
transmitted to the next generation.
2) Transgenerational Inheritance of Acquired
Traits
According to certain neo-Lamarckian
theories, acquired qualities can be passed down through generations by methods
other than genetic sequence alterations. Studies in this field have looked at
how a parent's lifetime attributes may affect the traits of their children. For
instance, there is evidence that certain diets or exposure to toxins may have
an impact on an animal's body size or metabolic properties throughout
generations.
3) Lamarckian Evolution in Microorganisms
Researchers have looked into the idea
of Lamarckian-type evolution in microbes, where environmental adaptations can
be quickly picked up and handed down to the following generation. The idea of
bacterial antibiotic resistance has been examined in relation to this issue.
