Final answer:
The challenges in identifying hominin fossils include a sparse and fragmentary fossil record, overlapping characteristics among species, and difficulty delineating the sequence of evolution due to simultaneous coexistence of multiple species. Postcranial and cranial evidence sometimes contribute conflicting information for classification.
Step-by-step explanation:
What are the problems involved in identifying hominin fossils? Identifying the lineage of hominin ancestors and their relation to present-day Homo sapiens poses several challenges. The record of hominin fossils is sparse and often fragmentary, which complicates the task of establishing clear evolutionary relationships. The sequence of hominin evolution is difficult to discern due to multiple hominin species coexisting at various times with several branches of the evolutionary tree not leading to modern humans. Moreover much of the evidence is based on incomplete skeletal remains, and sometimes researchers have to rely on either postcranial features or cranial evidence both of which can be misleading.
Characteristics that could potentially categorize a species under the genus Homo include brain size, skull shape, tool use facial features and limb adaptations for bipedalism. However the overlap of traits between different species adds to the difficulty in classification. Additionally new discoveries continue to change our understanding of human evolution making content loaded by new finds.