New footprints from Laetoli (Tanzania, 3.66 Ma). Discovery, analysis, inferences, research project and conservation plans

Fossil footprints are of great interest. A number of features help to identify their makers and can be used to investigate on biological and ecological issues. This is of crucial interest in palaeoanthropology, particularly in view of the emergence of our peculiar pattern of posture and locomotion. However, hominin footprints are rare and most of them are ascribed to the genus Homo. The only exception is represented by the trackways discovered in 1978 at Laetoli Site G, northern Tanzania, and referred to Australopithecus afarensis. These footprints were left on volcanic ashes about 3.66 million years ago by three bipedal creatures walking on a humid layer that was subsequently cemented. At Laetoli Site S (about 150 meters from Site G), we have unearthed new bipedal footprints of two different individuals, who were moving on the same palaeosurface, in the same direction and at the same speed as the three exposed at Site G. Our analysis based on advanced photogrammetric methods shows that the estimated stature and related body mass of one of the new individuals greatly exceed the estimates for those from Site G. This evidence supports marked intraspecific variation, pointing out the occurrence of a considerable difference in size between sexes and suggesting inferences on reproductive behaviour and social structure of these ancient bipedal hominins. A research project combined with conservation plans urgently needs to be developed and submitted to the Tanzanian Authorities for the knowledge, preservation and valorisation of such an extraordinary cultural heritage.