Final answer:
William Harvey in the 17th century first introduced the theory of epigenesis, which later influenced the modern understanding of epigenetic inheritance. His theory countered the preformationist notion that embryos merely grew from miniature adults in eggs or sperm. Current epigenetic concepts include mechanisms that affect gene expression without changing the DNA sequence, partially resonating with Lamarck's earlier ideas on the inheritance of acquired characteristics.
Step-by-step explanation:
The theory of epigenesis was first introduced by William Harvey in the 17th century. He used the term to describe the process by which embryos develop from undifferentiated masses into organized, differentiated structures, counteracting earlier preformationist ideas that suggested miniature adults existed within eggs or sperm. Harvey's concept laid the groundwork for later developments in embryology and modern understandings of epigenetic inheritance, which involves the transmission of gene expression patterns, in addition to DNA sequences, across generations.
While the idea of epigenesis can be traced back even further, the most notable and influential formulation came from Harvey. The term has since evolved, especially with the advent of molecular biology techniques, and current notions of epigenetics encompass mechanisms such as DNA methylation and histone modification, which do not change the DNA sequence but still have heritable effects on gene function.
This understanding of epigenetics has rekindled interest in some aspects of the earlier theories of French naturalist Jean-Baptiste Lamarck, who suggested the inheritance of acquired characteristics. Although Lamarck's ideas were largely rejected with the rise of Darwinian evolution, some components of his thinking appear to be in alignment with modern epigenetic studies. Nonetheless, it is important to note that epigenetic changes do not entail Lamarckian evolution; rather they provide a mechanism by which the environment can impact gene expression through generations without altering the fundamental DNA sequence.