The journey of artificial intelligence spans thousands of years, dating back to ancient myths and legends. While modern AI mostly emerged in the 20th century, its conceptual roots can be traced much further into the past. Here, we explore key milestones from the first century BCE until 1955 when John McCarthy coined the term 'artificial intelligence'.

Ancient Automata and Myths: The seeds of AI might be found in ancient mythology where automata, or self-operating machines, were common. For instance, Greek mythology features Hephaestus, the god of blacksmiths, who created mechanical servants. Similarly, ancient Chinese lore tells of Yan Shi, a mechanical engineer who reportedly constructed a humanoid figure.

Medieval and Renaissance Contributions: Between the Middle Ages and the Renaissance, the fascination with self-operating machines continued. Inventors like Leonardo da Vinci designed mechanical knights, and philosophers explored the concept of artificial beings.

The Age of Enlightenment: The 17th and 18th centuries saw significant theoretical advancements. René Descartes' work proposed that the body could be seen as a machine, laying foundational thoughts for later developments in AI. Similarly, the idea of rationalism and empiricism pushed forward by thinkers like John Locke and David Hume started shaping an empirical approach to understanding intelligence.

The 19th Century: This period was transformative with monumental contributions. Charles Babbage's Analytical Engine and Ada Lovelace's notes on it laid the groundwork for programmable computers. Lovelace is often celebrated as the first computer programmer, envisioning that machines could go beyond mere calculation.

Early 20th Century Pioneers: Moving into the 20th century, the focus began shifting towards formalizing logic and computation. Alan Turing and his Turing Machine model described a machine capable of performing any mathematical computation if it could be described by an algorithm. This was a stepping stone for the modern computer.

The Dawn of Modern AI: The period after World War II saw a surge in interest and research in AI. In 1955, John McCarthy, Marvin Minsky, Nathaniel Rochester, and Claude Shannon proposed the famous 'Dartmouth Conference' to explore the possibility of creating intelligent machines. This conference is widely considered the birth of AI as a formal academic discipline. McCarthy's pivotal role led him to coin the term 'artificial intelligence,' forever changing the trajectory of this field.

Understanding this timeline showcases how the curiosity and ambition of humans transcended eras to evolve into today’s AI technologies. From myths to mechanical knights, and from theoretical models to practical inventions, the history of AI is a testament to human ingenuity.