How did August Weismann challenge the inheritance of acquired characteristics?

August Weismann challenged the theory of the inheritance of acquired characteristics by proposing the germ-plasm theory. He argued that hereditary material, which he called germ plasm, is sequestered in germ cells and remains independent from the somatic (body) cells throughout an individual's life.12

Because the germ plasm is continuous and distinct from the body cells, changes acquired by an organism during its lifetime—such as those resulting from the use or disuse of organs—cannot be transmitted to the next generation. Weismann famously attempted to demonstrate this through experiments where he removed the tails of mice over several generations; the offspring consistently grew normal tails, providing evidence that physical mutilations were not inherited.132

By establishing that the continuity of germ plasm accounts for the inheritance of species characteristics, Weismann successfully highlighted the inadequacy of the evidence supporting Lamarckism and shifted biological thought toward a more critical, evidence-based understanding of heredity.3