Many sources postulate without much argumentation that Lamarcks evolutionary theory is "obviously incorrect". A classic example provided in such sources is the one with giraffes, in which Lamarck argued that the necks of these animals became long as a result of continually stretching to reach high foliage. This mechanism for adaptive change in response to the environment is considered wrong.

Now the counterargument to Lamarcks ideas comprises modern findings in genetics. So it is stated that organisms pass down traits through predetermined genetic information, not based on environmental adaptations during their lifetime. Furthermore, genetic research shows that living organisms cannot alter their genetic material as needed.