Darwin developed the theory of evolution to explain why there are so many different kinds of living things. He could easily observe that offspring of any animals were slightly different from their parents and that this could allow for big changes over thousands of years. He did not know that genes caused the differences. Genes are now very important in the modern theory of evolution.

Darwin explained how small inherited differences could accumulate over many generations, but he did not know what caused those differences. Modern evolutionary theory incorporates genetics, which explains how traits are inherited and how variation arises. Therefore, it includes new research involving genes and evolution, not changes to Mendel’s laws.

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