The large amount of size variation observed within H. erectus, taken primarily from fragmentary fossil remains, makes it difficult to estimate average levels of dimorphism.
Two of the more significant, yet elusive, questions about H. erectus concern the levels of sexual dimorphism within the lineage and the capacity for language. Sexual dimorphism, the physical differences between males and females, is an important source of variation within species, and in primates can be an indicator of reproductive strategy and group dynamics. Sexual dimorphism, given its role in intraspecific variation, can also be a confounding factor in proper taxonomic identification. The large amount of size variation observed within H. erectus, taken primarily from fragmentary fossil remains, makes it difficult to estimate average levels of dimorphism. The H. erectus fossil record provides clear evidence of a large range of skeletal size variation, at least equivalent to that observed in living human populations, but it does not provide conclusive evidence that males were systematically larger than females to a greater extent than they are today. If H. erectus did have more sexual dimorphism than H. sapiens, we would infer that male competition for mates was more dependent on body size than it is today.