How did Charles Darwin’s theory of natural selection differ from Lamarckism?

Lamarckism and Charles Darwin’s theory of natural selection differ fundamentally in how they explain the adaptation and evolution of species.

Lamarckism, proposed by Jean-Baptiste Lamarck, centers on the "inheritance of acquired characteristics." It suggests that organisms change during their lifetimes by adopting new habits in response to their environment, which strengthens or weakens specific organs through use or disuse. These acquired physical changes are then passed directly to offspring.1

In contrast, Darwin’s theory of natural selection posits that individuals within a population possess natural variations. Because more individuals are produced than can survive, those with variations that provide even a slight advantage in their environment are more likely to survive and reproduce, passing those favorable traits to the next generation.2

While Darwin himself was not entirely opposed to the idea of acquired characteristics—even proposing a "provisional hypothesis" called pangenesis to explain it—his primary contribution was the mechanism of natural selection. Unlike Lamarckism, which relies on the direct influence of the environment on an organism's body, natural selection acts as a filter that preserves beneficial variations already present in a population.342