A recent preliminary study by Ph.D. student Leonie Hoff of the University of Oxford, published in the Oxford Journal of Archaeology, provides insight into how ancient fingerprints left on terracotta figurines reveal the age and sex of their makers.
Female fingerprints typically contain more densely packed ridges than male prints in the same area. These measurements were then compared against ridge density patterns found in contemporary Egyptian populations. ... The sex could not be determined for children.