What is the proof...

[Arjun]

How can one say that the reason behind girrafe neck is lamarkis
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[biohazard]

One cannot say so, really.

Lamarckism was a theory that tried to explain how giraffes got their long necks (by inheriting achieved traits), but it turned out Lamarck got his idea wrong.

However, Jean-Baptiste might find some comfort from the today's discovery of epigenetics, a mechanism that may affect the expression of certain genes (due to environmental factors, for example) and these "achieved" expression patterns can be inheritable.

[phamquocdat41191]

(sorry if my english is not good)
According to Lamarck, giraffes in the long past had short neck. however, they want to eat leaves from high trees, so they have to evolve their necks longer. Each generation, their neck got a little longer, for example, 5 mm. Remember, Lamarck believe that evolution is a very long progress. environment changes very slowly, so organisms change to respond to their environment, very slowly. After a long time of evolving, giraffes got their long neck like today.
Remember one thing, Lamarck's theory is now proved wrong for some reasons such as:
- he could not differentiate between heritable variation and inheritable variation.
- he claimed that every organism responds the same to the changes of environment.
- he could not explain the trend of evolution from simple to complex. He believed that organisms have the trend to perfect themselves.
The reason you still have to study Lamarck is because he is the first person making theory about evolution, while others think that god makes us all.

[futurezoologist]

I dont quite think that the evolution of giraffes necks occured at 5 mm per generation otherwise their necks would be far longer than they are now and also because evolution works on genetic variation and mutation (amongst a few other things), so it doesn't jut grow 5mm per generation because they 'want it to'. Imagine tens of thousands of years ago the climate is changing and trees are adapting to become taller from shrubs to canopy trees, the giraffes are short enough so they can only reach the bottom third of the tree, now image the advantage that a giraffe would have if he were taller than the others, even just 20cm taller, this giraffe would have no intraspecific competition at all, so this giraffe would have much more chance of survival and breeding rights and therefore be able to pass on these genes of his(whether his genes game from genetic variation or mutation) more easily than those without this advantage, thus evolution.

[phamquocdat41191]

(sorry if my english is not good)
Oh, futurezoologist, what you said is just right. However, I don't express the idea of evolution according to modern opinion or Darwin Opinion. What I did is show opinion of Lamarck. Of course it is totally wrong today.

[futurezoologist]

Oh i see sorry.