Fossil analysis reveals that an ancestor of modern humans would have made a terrible hitch-hiker.

Past reconstructions of the hands of the hominin Australopithecus afarensis assigned scattered bones to individuals and single fingers. Campbell Rolian at the University of Calgary, Canada, and Adam Gordon at the State University of New York at Albany reanalysed an assembly of A. afarensis bones to better account for uncertainties in the fossil record.

Their results suggest that the hominin had shorter thumbs than was thought, with proportions more closely resembling those of gorillas. Although A. afarensis may have been able to bring the tips of its fingers and thumbs together, its thumbs were not long enough for the precision grip that later hominins used to craft stone tools.

Am. J. Phys. Anthropol. 152, 393–406 (2013)