Calico Early Man Site, California

A controversial archeological site, which suggests that humans have been in North America as early as 100,000 years ago. Louis Leakey was the project director at Calico until his death in 1972, and it was the only New World site he worked on. One of the basic controversies centers on the interpretation of features found on small stone artifacts. The site's original primary archeologist, the late Ruth Dee Simpson, claimed that the rough points on some of the rocks were formed by man, while others maintained that they were naturally formed - not artifacts at all, but geofacts. Researchers continue to evaluate which interpretation is correct.