They do not have the dramatic visual appeal of Chauvet or Lascaux.

The bones they contain are mostly fragmentary, brown with age, indistinguishable to the untrained eye from the natural accumulations of animal remains that are common in cave sites.

But the marks on those bones — invisible without magnification, invisible without training, invisible without the specific knowledge of what to look for and what it means — are among the most significant physical evidence for human presence in North America that has ever been found.

The cut marks on the horse mandible, confidently attributed to a stone tool by trained taphonomic analysis, directly dated by AMS radiocarbon to approximately 24,000 calibrated years before present, represent the oldest well-documented evidence of human activity in North America.