Why do archaeologists and historians try to find artifacts and writings from ancient civilizations?
Archaeologists and historians seek in ancient transcripts, fossils, structures and other artifacts a greater understanding of the history of mankind and of the world in which we live. By digging for dinosaur fossils, for example, archaeologists and paleontologists hope to attain better knowledge of living species that occupied the planet before the advent of homo sapiens both to understand how these creatures lived and, as importantly, to understand how and when they disappeared. If it is determined through archaeological, chemical, meteorological and astronomical research why dinosaurs disappeared, we can have a better appreciation for threats to humanity that may originate from beyond our solar system (e.g., asteroids and meteorites) and from threats to humanity that may result from such phenomena as climate change (i.e., was the disappearance of the dinosaurs the inevitable result of major transformations in the climates where they had previously lived).
Archaeological and historical research into ancient civilizations serves much the same purpose. By better understanding how certain ancient civilizations lived, and why they ultimately perished, we can better understand the threats that may confront contemporary civilizations. Whether the Incas, Mayan, and Aztecs, for instance, were ultimately undone by their own actions, by outside invaders (including Spanish conquistadors and invisible germs alike), or by natural phenomena like catastrophic weather and earthquakes can all be determined, and can only be determined, through archaeological and anthropological research. This all involves protracted, painstaking research, sometimes at great personal risk to the scientists and historians involved, but is all essential to our understanding of human history -- knowledge that may help modern humans better navigate the perilous paths ahead as we confront resource shortages, overpopulation, and other developments.