There is no definitive evidence for a lightstructure earlier than the Pharos of Alexandria. However, there is much indirect evidence. Whether the story of Hero and Leander is myth or historical fact is irrelevant. The mythology of the ancient culture of the Greeks and the Trojans clearly refers to the idea of constructing navigational aids for those who use the sea. It is surely inconceivable that, given the prevalence of these ideas, no structures were built. There is unambiguous evidence linking the stories with recognisable places in the 21st century landscape. Thus, it is possible that the first lightstructure was indeed at Abydos on the Hellespont, although we have no other evidence than the texts written in Roman times and we have no clear indication of a date.
The evidence at Troy is more positive. Troy was the earliest major city with a clear dependence upon sea borne traffic that would have constructed artificial aids to navigation. There is every possibility that the idea, expressed in a story of Hero showing a navigation light for Leander, had some element of truth. We might conclude that it was followed up by the construction of a lightstructure at Cape Sigeum on southern side of the entrance to the Hellespont. Here was a most important and strategic waterway where the sheer amount of traffic justified the effort and expense of construction. Here also was the burial site of the greatest Greek warrior. We can place the time of this event as occurring somewhere during the long period of stability of Troy VI, i.e. from 1,700 BC to 1,250 BC.
The possibility that the Phoenicians built the first lightstructure at Cadiz cannot be ignored, but remains most unlikely, unless the Sigeum structure was never built. Although Cadiz was possibly founded in 1110 BC, it was argued above that a more likely date is some 300 years later. The extended discussion about the Phoenicians, their culture and their methods tends to render the argument unlikely. Even if it did exist, the lightstructure at Carthage would only qualify as the first lightstructure in the absence of structures at Sigeum and Cadiz. If it can be shown that structures at Cadiz and Carthage were indeed built (although we are not convinced) it is far more likely that the Phoenicians, having seen the lightstructures on the Hellespont, adopted the idea for their own ports. There are no other sites where earlier lightstructures can be proposed, consistent with the ideas of their association with the development of civilisation and culture. Our study has examined the stages of development of other civilisations of the Mediterranean. Therefore we can be confident, but not certain, that the most likely occasion that a lightstructure was first constructed was on the southern entrance to the Hellespont at Cape Sigeum, an act strongly associated with the highly developed culture of Troy.
Nothing lasts forever in history, and there were many times when these lighted sites became dark. The structures became victims of the regular battles and changing politics. Indeed, it is also possible that lightstructures were not lit in winter and thus only temporary. But the seed of the idea, once sown, remained present in the roots of subsequent interacting cultures. Copied occasionally at first, the idea evolved in a number of forms around the Mediterranean between 1,250 and 300 BC, only to be celebrated in glorious style by the building of the great Pharos itself.
We shall almost certainly never be able to verify the story of Hero and Leander. However, many of the ancient sites on Turkish soil remain unexcavated and there is every chance that archaeology will, in years to come, unearth a new structure that can be unambiguously interpreted as a lightstructure and dated to the same period, if not earlier.