I have been told by a highly authorative professorial source that the very latest evidence indicates that the human eye would take at least 5.0 billion years to evolve. How is this possible if the Earth is only 4.54 billion years old?

The assertion that the human eye would take at least 5.0 billion years to evolve likely involves a misunderstanding. The Earth is approximately 4.54 billion years old, and life has existed on Earth for a significant portion of this time, with multicellular organisms and more complex life forms evolving over the last few hundred million years. The human eye, like other complex biological structures, evolved through a series of gradual steps over millions of years as a result of natural selection. There is no credible scientific evidence suggesting that the evolution of the eye takes 5 billion years or more; rather, evolutionary biology indicates that simpler forms of eyes and light-sensitive cells began evolving much earlier in Earth's history, and sophisticated eyes have appeared in various lineages at different times. For example, the basic structure of the eye has evolved independently in different species, indicating a long evolutionary history of various forms of photoreception. Simple light-sensitive spots can be found in some of the earliest multicellular organisms. The evolution of more complex eyes, such as those found in vertebrates and cephalopods, occurred over much shorter timescales. To sum up, while the evolution of complex structures like the human eye takes considerable time, it is not at all inconsistent with the age of the Earth. Any claim suggesting an evolution time frame exceeding the age of the planet should be re-evaluated in the context of established evolutionary theory and the fossil record.