In 2003, archaeologists from Indonesia and Australia discovered the bones of a new species of human, named Homo floresiensis, in a cave on the Indonesian island of Flores. Its short stature – about 3.5 ft (1.1 m) – quickly earned Homo floresiensis the nickname of the "hobbit", and ever since its discovery, scientists have been debating where it fits on the human evolutionary tree. According to a new study from the Australian National University (ANU), the species branched out from a common ancestor of ours much earlier than previously thought.
Just how close a relative to us is the hobbit? One theory suggests that they are just modern humans, albeit ones suffering from a congenital condition called microcephaly, which leads to a much smaller brain, head and body. A more widely accepted origin story says floresiensis evolved from Homo erectus, an ancestor of ours that lived between 1.9 million and 70,000 years ago, but on closer inspection, the ANU researchers don't believe that's the case, either.
"We can be 99 percent sure it's not related to Homo erectus and nearly 100 percent chance it isn't a malformed Homo sapiens," says Mike Lee, co-author of the study.
The ANU study involved close analysis of 133 data points from the hobbits' whole skeleton, including its skull, jaws, teeth, arms, legs and shoulders. In some ways, particularly the jaw, Homo floresiensis appears to be more primitive than Homo erectus.
"Logically, it would be hard to understand how you could have that regression – why would the jaw of Homo erectus evolve back to the primitive condition we see in Homo floresiensis?" says Dr Debbie Argue, lead author of the study.
The researchers believe Homo floresiensis was instead related to the earlier species, Homo habilis. "The analyses show that on the family tree, Homo floresiensis was likely a sister species of Homo habilis. It means these two shared a common ancestor," says Dr Argue.
Homo habilis is one of the earliest known hominids, walking the Earth between 2.1 and 1.5 million years ago. Going back earlier than that, the line between human and ape begins to blur. Although the hobbit remains have been dated to between 100,000 and 54,000 years old, the study suggests the species could have branched off as early as 1.75 million years ago.
"It's possible that Homo floresiensis evolved in Africa and migrated, or the common ancestor moved from Africa then evolved into Homo floresiensis somewhere," says Dr Argue.
The research is published in the Journal of Human Evolution.
Source: Australian National University