LAS VEGAS — A famous trail of footprints once thought to have been left behind by a family of three human ancestors may have actually been made by four individuals traveling at different times.

In a new examination of Laetoli in northern Tanzania, where a 3.6-million-year-old track of footprints of the bipedal human ancestor Australopithecus is preserved, researchers now argue that the classic understanding of this site is mistaken. The footprints have been buried since the mid-1990s for preservation, but a section recently opened for study as Tanzanian officials make plans for a museum on the site....