Lamarck's theory cannot account for all the observations made about life on Earth. For instance, his theory implies that all organisms would gradually become complex, and simple organisms disappear.

What is wrong with Lamarck's concept of evolutionary process?

A major downfall of his theory was that he could not explain how this might happen, though he discussed a "natural tendency toward perfection." Another example Lamarck used was the toes of water birds. ... By the same token, Lamarck believed that disuse would cause a trait to become reduced.

What disproved Lamarck's theory of evolution?

Lamarck. s .. Theory of Acquired characters.. was disproved by August Weismann who conducted experiments on mice for twenty generations by cutting their tails and breeding them.