Bipedal trackways discovered in 1978 at Laetoli site G, Tanzania and dated to 3.66 million years ago are widely accepted as the oldest unequivocal evidence of obligate bipedalism in the human lineage^1,2,3. Another trackway discovered two years earlier at nearby site A was partially excavated and attributed to a hominin, but curious affinities with bears (ursids) marginalized its importance to the paleoanthropological community, and the location of these footprints fell into obscurity^3,4,5. In 2019, we located, excavated and cleaned the site A trackway, producing a digital archive using 3D photogrammetry and laser scanning. Here we compare the footprints at this site with those of American black bears, chimpanzees and humans, and we show that they resemble those of hominins more than ursids. In fact, the narrow step width corroborates the original interpretation of a small, cross-stepping bipedal hominin. However, the inferred foot proportions, gait parameters and 3D morphologies of footprints at site A are readily distinguished from those at site G, indicating that a minimum of two hominin taxa with different feet and gaits coexisted at Laetoli.

1978 年在坦桑尼亚 Laetoli G 遗址发现的双足足迹可追溯到 366 万年前，被广泛认为是人类谱系中专性双足行走的最古老明确证据^1,2,3。两年前在附近地点 A 发现的另一条轨道被部分挖掘并归因于人科动物，但与熊（熊科动物）的好奇亲缘关系使其对古人类学界的重要性边缘化，这些脚印的位置变得模糊不清^3,4,5. 2019 年，我们定位、挖掘并清理了现场 A 轨道，使用 3D 摄影测量和激光扫描制作了数字档案。在这里，我们将这个地点的足迹与美洲黑熊、黑猩猩和人类的足迹进行比较，我们发现它们更像人科动物而不是熊科动物。事实上，狭窄的步幅证实了最初对小型交叉步进双足类人的解释。然而，推断出的 A 点足迹比例、步态参数和 3D 形态足迹很容易与 G 点足迹区分开来，这表明至少有两个具有不同足部和步态的古人类类群在 Laetoli 共存。