They knew that traits were passed down from parents to offspring, but they didn't know how. This led to several problems:
* Blending inheritance: They initially thought traits blended together like paint, meaning variation would be lost over time. This would prevent natural selection from working.
* Lack of explanation for the origin of variation: Without understanding how traits were inherited, it was unclear how new variations arose in the first place.
It wasn't until Gregor Mendel's work on pea plants in the mid-1800s that the basis of inheritance was understood. His work laid the groundwork for genetics, which explained how traits are passed down through discrete units (genes) and how variation arises through mutations.
This discovery was essential to solidifying natural selection as the primary driver of evolution. It explained:
* How variation is maintained: Genes are passed down independently, preventing blending and allowing for diverse traits to persist.
* How new variation arises: Mutations are the source of new genetic variations that natural selection can act upon.
The integration of genetics with Darwin's theory of natural selection created the modern synthesis of evolutionary theory in the early 20th century, providing a comprehensive understanding of how evolution works.
