Skull suggests three early human species were one

@article{Perkins2013SkullST,
  title={Skull suggests three early human species were one},
  author={S. Perkins},
  journal={Nature},
  year={2013}
}
Controversial analysis of long-faced fossil proposes that Homo erectus should subsume two other hominin species. 
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References

A Complete Skull from Dmanisi, Georgia, and the Evolutionary Biology of Early Homo
TLDR
The Dmanisi sample, which now comprises five crania, provides direct evidence for wide morphological variation within and among early Homo paleodemes, implying the existence of a single evolving lineage of early Homo, with phylogeographic continuity across continents. Expand