The ancient remains of two human-like creatures found in South Africa could change the way we view our origins.
The 1.9-million-year-old fossils were first described in 2010, and given the species name Australopithecus sediba.
But the team behind the discovery has now come back with a deeper analysis.
It tells Science magazine that features seen in the brain, feet, hands and pelvis of A. sediba all suggest this species was on the direct evolutionary line to us - Homo sapiens.
"We have examined the critical areas of anatomy that have been used consistently for identifying the uniqueness of human beings," said Professor Lee Berger from the University of the Witwatersrand in Johannesburg
"Any one of these features could have evolved separately, but it is highly unlikely that all of them would have evolved together if A. sediba was not related to our lineage," the team leader informed BBC News.
It is a big claim and, if correct, would sideline other candidates in the fossil record for which similar assertions have been made in the past.
Theory holds that modern humans can trace a line back to a creature known as Homo erectuswhich lived more than a million years ago. This animal, according to many palaeoanthropologists, may in turn have had its origins in more primitive hominins, as they are known, such as Homo habilis or Homo rudolfensis.
The contention now made for A. sediba is that, although older than its "rivals", some of its anatomy and capabilities were more advanced than these younger forms. Put simply, it is a more credible ancestor for H. erectus, Berger's team claims.
The sediba specimens were unearthed at Malapa in the famous Cradle of Humankind World Heritage Site, just to the northwest of Jo'burg.They were pulled from a pit - a depression left in the ground by a cave complex that had lost its roof through erosion over time.
Identified as an adult female and a juvenile male, the two individuals were quite possibly mother and son. What seems certain is that they died together in some tragic accident that saw them either fall into the cave complex or become stuck in it. After death, their bodies were washed into a pool and cemented in time along with the remains of many other animals that got trapped in the same way.
In the months since their 2010 announcement, Professor Berger and colleagues have subjected the remains to further detailed assessment.
Age: The latest dating technologies were applied to the sediments encasing the fossils. Whereas original estimates had put the age of the remains at somewhere between 1.78 and 1.95 million years old, the new analysis has narrowed this window of uncertainty to just 3,000 years. The new age is now between 1.977 and 1.98 million years old. The refined dating is important, says the team, because it puts A. sediba deep enough in time to be a realistic ancestor to H. erectus.