1. Jean-Baptiste Lamarck (1744-1829) and the Theory of Inheritance of Acquired Characteristics: Lamarck proposed that organisms could pass on traits they acquired during their lifetime to their offspring. For example, he believed that giraffes evolved their long necks because their ancestors stretched them to reach high leaves. While this theory was later disproven, it was a significant attempt to explain how organisms changed over time.
2. Erasmus Darwin (1731-1802) and the Concept of Common Descent: While not a fully-formed theory of evolution, Erasmus Darwin (Charles Darwin's grandfather) proposed that all life originated from a common ancestor. He observed similarities between different species and believed that changes over time led to the diversity of life. His ideas laid some groundwork for his grandson's later theory of evolution by natural selection.
It's important to note that neither Lamarck nor Erasmus Darwin proposed the mechanism of natural selection as the driving force behind evolution. That concept was later developed by Charles Darwin and Alfred Russel Wallace in the mid-19th century.
