Neo lamarckism
Lamarck’s ‘theory of inhertitance’ was further studied by a group of
scientists. Their ideas supporting Lamarck’s opinion collectively constitute
neo Lamarckism.
The neo Lamarckians were of the opinion that ‘adaptions’ are
universal in nature. An adaptation happens through causal relationship of
structure, function and environment. Due to changes in the environment, habits
and life style of organism gets altered. Thus gradually the organism acquires
new structures. The newly obtained character gradually becomes an
inheritable trait. This opinion and argument is a modified form of
Lamarckism. These ideas stressed direct action of environment on organisms.
Support to neo-Lamarckian concept – Experiments (Neo lamarckism)
Neo Lamarckism
1. McDougall (1938) tried to prove that learning is an acquired character
that can be inherited. He did his experiments on rats.
He deviced a ‘T’ shaped tank. The tank had two exits. One exit was
well lighted. However at the terminal region of the exit he deviced an
arrangement for giving electrical shock. The pathway to the other exit was
kept dark. At the terminal exit point a small piece of cheese was kept as a
reward. McDougall dropped several rats into the tank. Many of the rats
preferred lighted pathway to escape and at the exit they received electric
shock. Those rats, that preferred dark pathway received the cheese. He
repeated the trial several times. Gradually many rats learnt the correct route
for escape. Subsequently the rats were allowed to breed and the next
generation developed.
The same experiment was repeated in the second generation. (Neo lamarckism)
According to Mc Dougall, it was claimed that the number of mistakes
committed, gradually got reduced. The speed of learning increased from generation to generation. Thus he concluded that learning is an acquired
character.
However later workers found some technical mistakes in the work
of Mc Dougall. The same experiment while repeated in other laboratories
failed to give similar results. (Neo lamarckism)
2. Temperature related changes in the body of mice was noted by F.B.Sumner
(1910). He reared one set of white mice in warmer temperature (20 – 300c)
and another set in cold conditions. He found that in warmer conditions the
mice developed larger ears and longer tails. He further claimed that these
characters were inherited.
Through similar works claim for inheritance of acquired characters
were made by Lindsey, Guyer and Smith and Kammerer. In all these works
while repeating, critics have found technical mistakes and rejected them
outright.
However, the controversy over ‘inheritance’ of acquired characters
still continues. This theory of Lamarck while has not been disproved totally,
it remains to be proved correct. (Neo lamarckism)
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