There is a lot of history, an understanding that Native Americans were pretty good at understanding of what they were looking at, art from before Europeans show up until recent, bits of religion, the whole deal is brought together for the modern reader.
I believe this book is a perfectly logical assumption that people in ancient times knew as much or more about fossils and what came before our lives as we do now, and usually with less fuss.
The book begins by describing one of the first fossil elephant finds in America -- by a party of Abenakis. (The Mesoamerican legends were more similar to the ancient Europeans in this regard.) The reasons for this may be that as a result of geological differences, North American fossil fauna are often found complete and reasonably articulated, while the Mediterranean fossils are usually scattered and fragmentary, and mixed together; and that many North American remains are of relatives of animals living in the same areas, like giant bison and cave bears, while the European fossil remains are of elephants, giraffes, rhinoceros, and other animals the Greeks and Romans only came in contact with very late if at all.
She set herself a much harder task in this book, in tracing Native American awareness and understanding of fossil remains via stories and myth-making, since most Native cultures are oral and therefore prior to the relatively modern era left little in the way of written evidence of myths and beliefs. For a start, it would be impossible to replicate the thoughts and beliefs of earlier generations of Native Americans; for all that their culture is predominately oral, it is virtually impossible to believe that modern stories and myths can have been handed down over decades and centuries within any change, modification or influence from current knowledge.
It is a difficult line to walk between respecting Native American traditions and beliefs and paleontological principles and research. All in all, Fossil Legends of the First Americans gives a well researched walk-through on many Native American myths, legends, and beliefs regarding fossils.
I found that off-putting and sort of naive (especially in her interpretation of the early paleontologist George Gaylord Simpson -- his accounts of Native American people having little to no intelligence, no ability to understand paleontological finds, etc., Mayor excused as "a product of his time" or argued that provided with the proper evidence, Simpson would have changed his opinion of the Native peoples' aptitude for intelligence), whereas from the textual accounts that Mayor provided of Simpson's writing, I read him more as a simple through and through racist.
Her approach is to make inferences based on possible references to fossils and extinct animals, and to connect these references to confirmed cases where fossils were referenced or used. It makes sense that a group of people who had been living in a particular place for a very long time would be aware of and influenced by these objects and that knowledge of now-extinct Pleistocene animals would be preserved in tradition.
As an academic, I appreciated the meticulous and wide-ranging research that went into it, but even more than that, as a storyteller I appreciated the absolute respect with which Mayor handled indigenous culture and tradition.