Here's why:
* Acquired characteristics are not encoded in DNA: Changes that occur during an organism's lifetime, like a muscle growing larger through exercise, are not changes to the genetic code. These changes are not passed on to offspring.
* DNA is the blueprint for inheritance: Evolutionary change happens through changes in the DNA sequence, called mutations. These mutations can be beneficial, harmful, or neutral. Beneficial mutations are more likely to be passed on to offspring, leading to gradual changes in populations over time.
* Natural selection is the driving force: The environment "selects" for organisms with traits that make them better adapted to survive and reproduce. This means that individuals with beneficial mutations are more likely to pass on their genes, leading to the spread of those traits.
Examples of Lamarckism disproven:
* Giraffe necks: Lamarck believed giraffes stretched their necks to reach higher leaves, and this stretched neck was passed on. However, modern understanding shows that giraffes with longer necks were better adapted to their environment and reproduced more successfully, leading to the evolution of longer necks over time.
* Bodybuilders: If a bodybuilder develops massive muscles through intense training, their children will not inherit those muscles. Their children will inherit the genes that influence muscle potential, but the actual development of muscle mass will depend on their own training and genetics.
In summary: Evolution occurs through the inheritance of genetic changes, not acquired characteristics. Lamarckism is a discredited theory, and the modern understanding of evolution is based on Darwin's theory of natural selection and the inheritance of genetic traits.
