The Lamarckian theory of inheritance- A (not entirely) wrong way to view evolution

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Charles Darwin was not the first scientist to think about evolution. Of those who came before him, one is particularly famous: Jean-Baptiste Lamarck. In the early 19th century, Lamarck came up with a complicated and detailed evolutionary framework in which species were compelled to gain complexity over time. However, there are two concepts he championed as part of this framework for which he is now famous. The first is the idea that organisms change during life in response to their environment – they acquire new characteristics – the second is that the organism’s offspring inherit these acquired changes. Decades after Lamarck’s death, these two ideas became known as the Lamarckian theory of inheritance.

Jean-Baptiste Lamarck // 1744–1829
Jean-Baptiste Lamarck // 1744–۱۸۲۹

Perhaps surprisingly, Lamarckism remained popular even after Darwin had published On the Origin of Species in 1859. In fact, in the late 19th century and early 20th century many scientists were sceptical about Darwin’s theory of evolution by natural selection. During this period – sometimes called the “Eclipse of Darwin” – many argued that evolution was actually driven by the inheritance of acquired characteristics. In essence, they argued that evolution was Lamarckian not Darwinian. It was only when scientists rediscovered the work of Gregor Mendel and began to see evolution through the prism of genetics that Darwin’s idea of natural selection became popular again.

There is a postscript to the story. Genetic studies largely disproved Lamarckism. In the last few years, though, strange exceptions to this rule have emerged. For instance, some bacteria “hardwire” life experiences into their DNA, meaning their offspring do in fact inherit features acquired by the parent cell. In some circumstances Lamarckism apparently does occur.

The giraffe’s long neck – an evolutionary puzzle Lamarck’s theory seemed to solve.

One way to think about the broadly disproved Lamarckian theory involves giraffes. During its life, the (short-necked) ancestor of the giraffe strained to nibble leaves from tall trees. This literally stretched the animal’s neck, making it slightly longer. Lamarckism suggests that the giraffe’s offspring inherited this feature: at birth, their necks were slightly longer than their parents had been when they were born. Later in life, these offspring also strained to feed, so their necks stretched a little more. When they reproduced, their offspring began life with even longer necks. Countless generations of this process gave rise to the modern giraffe, with a neck that can be almost 2 metres (6 feet 6 inches) long.

Lamarckism theory, rejected by most biologists, suggests that organisms adapt to their environment throughout life and then pass these acquired changes on to their offspring.

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It suggests evolution is driven by experiences gained in life.

   

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