The Nature article seems to be on a different fossil that indicates that
there was diversity among early Homo because more primative features are
found in the fossil than are found in older fossils. This just means
that at least one lineage with more ancestral features was
contemporaneous with other lineages with more derived characters.
The Science articles are claiming that they have found a partial
mandible with features associated with Homo that is much older (over
2.58 million years) than the Habalines that have been found to date.
Ron Okimoto