Answer:
Several evidences were found that supported the ideas defended by Darwin. As a result, Lamarck's ideas became obsolete.
Explanation:
Although we currently use Darwin's theories to explain the evolutionary processes of living beings, this has not always been the case. For a long time, Lamarck's theory of how living beings evolved was the theory accepted as correct.
Lamarck's theory is known as the "law of use and disuse". This law states that living beings have evolved because they have started to use a feature a lot, which has been developing more than the others. For example: In Lamarck's theory, giraffes had a large neck because, one day they had a small neck, but they stretched so far to reach the leaves of the trees that the neck developed, until it reached the height we know.
Although Darwin's theory of natural selection makes much more sense, it was only considered by scientists after much evidence about evolution was discovered. This evidence supported Darwin's theories, but made Lamarck's obsolete.