The march of History versus the march of Science

In Coursera, Yuval Noah Harari's first lecture on the history of mankind is described thusly:

Lecture 1: The Human Family
One hundred thousand years ago, at least six different species of humans inhabited planet Earth. Our species, Homo sapiens, was just one among them. Who were the others? Where did they come from? And what happened to them? Why is there today only one species of humans—Homo sapiens?

I find it amusing to note that the New York Times recently reported this:

After eight years spent studying a 1.8-million-year-old skull uncovered in the Republic of Georgia, scientists have made a discovery that may rewrite the evolutionary history of our human genus Homo.

It would be a simpler story with fewer ancestral species. Early, diverse fossils — those currently recognized as coming from distinct species like Homo habilis, Homo erectus and others — may actually represent variation among members of a single, evolving lineage. 

In other words, just as people look different from one another today, so did early hominids look different from one another, and the dissimilarity of the bones they left behind may have fooled scientists into thinking they came from different species. 

This was the conclusion reached by an international team of scientists led by David Lordkipanidze, a paleoanthropologist at the Georgian National Museum in Tbilisi, as reported Thursday in the journal Science.

The reason the skull tells us so much is because it is "“the world’s first completely preserved adult hominid skull” of such antiquity."

If this finding stands, then there were no six species of humans one hundred thousand years ago, and Harari's first lecture will be history.