Every announcement of a new hominid species prompts questions and debate: Is it really a new species? What characteristics set it apart from known species? Where does it fit on the family tree? But few discoveries have been as head-scratching as that of Homo floresiensis, better known as the “Hobbit” species.
In 2003, researchers discovered a cache of fossils—partial skeletons of at least nine individuals—on the island of Flores in Indonesia. What made them remarkable was that the most complete remains belonged to a 30-year-old female who stood 3½ feet tall, with a brain the size of a chimp, and who lived only 18,000 years ago. How did these early humans get so small? Had they evolved from a larger early hominin? Did they evolve elsewhere and then come to Flores? Could they be merely abnormal Homo sapiens?
A study released Friday in the journal PLOS ONE argues that H. floresiensis is indeed a distinct species, one that evolved from Homo erectus. H. erectus is by far the most successful hominin species in terms of how long it lasted. It is believed to have evolved 1.9 million years ago and endured until some point within the last 100,000 years. Along the way, H. erectus spread from Africa to Turkey and Asia, may have been the first species to control fire, and made advances in the stone tool technology first employed by Homo habilis.
Japanese paleoanthropologist Yosuke Kaifu and his fellow researchers did an exhaustive study comparing 40 teeth of floresiensis to hundreds of teeth of other species, including Homo habilis and Homo ergaster from East Africa, a Homo erectus from Java, and two ancient Homo specimens from East Asia.
The teeth were similar in size to those of smaller modern humans, implying that H. floresiensis could be unusual examples of Homo sapiens, but the teeth included too many primitive traits for that to be the case. The scientists then determined that those traits were more in line with H. erectus than with the older Homo habilis or perhaps an even older Australopithecus series.
"For me, this work will turn the tide about the question of evolutionary origin of H. floresiensis," Kaifu told Live Science.
There is more significance to the study than just declaring that H. floresiensis is indeed its own species. Ruling out those ancient ancestors for H. floresiensis argues against the idea that a species before H. erectus might have migrated out of Africa. It is also in line with previous artifacts discovered on Flores. Mike Morwood, the archaeologist who discovered H. floresiensis in 2003, had previously found crude stone tools of the sort used by H. erectus, dating to 840,000 years ago.
As the authors conclude in the new study, "H. floresiensis is not evidence for unexpectedly early hominin dispersal into Asia but is more likely an example of considerably greater flexibility in hominin physical evolution as originally proposed."