Many sources postulate without much argumentation that Lamarck's 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 Lamarck's 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.
- Doesn't the latter contradict the evolutionary theory itself, which states that nature (i.e. environment) shapes species through natural selection in the environmental milieu? If it is not the environmental/natural factor that is responsible for genetic evolution, then what is?
- If genetic material were to be unchangeable, then how would adaptation to the environment and consequent evolutionary change would ever be possible? The genotype (following this logic) would remain the same.
- And lastly, maybe giraffes do not develop long necks at such a rapid pace (as Lamarck probably thought) by simply stretching their necks in one generation; however, what, if not neck stretching, is responsible for their consistently longer necks throughout thousands or millions of years? Hadn't the environment gradually shaped their genotype? Similarly, if I run more often, maybe my children will not become more fit, but isn't it just a matter of time (thousands of years) that if all of us consistently run a lot, then our offspring will eventually become more fit? Wouldn't our voluntary efforts eventually enhance our genetics? I do not see any problem with Lamarck's logic at all, except probably the time frame.