An Australian National University-led team of researchers has found that Homo floresiensis — a dwarfed human species that lived until about 50,000 years ago on a remote Indonesian island — most likely evolved from a very primitive ancestor on the African continent, and not from the rather modern Homo erectus as has been widely believed. Details of the research are published in the Journal of Human Evolution.
According to Argue et al, Homo floresiensis is a long-surviving relict of an early hominin lineage and an unknown migration out of Africa, and not a recent derivative of either Homo erectus or Homo sapiens. This image is an artist’s impression of Homo floresiensis. Image credit: Katrina Kenny.
The skeletal remains of Homo floresiensis were found in 2003 in Liang Bua Cave on the island of Flores, Indonesia.
Since the discovery, a wide range of potential explanations for the evolution of this hominin has been explored.
“One view is that Homo floresiensis is a distinct species, derived from Asian Homo erectus that arrived on Flores and subsequently evolved a smaller body size, perhaps to survive the constrained resources they faced in a new island environment,” the study authors said.
“Fossil remains of Homo erectus, well known from the Indonesian mainland of Java, have not yet been discovered on Flores,” they noted.
“The second idea is that Homo floresiensis is directly descended from an early Homo lineage with roots in Africa.”
“The third is that Homo floresiensis is not a valid species, but is instead a pathological population of anatomically modern humans that had genetic or metabolic disorders.”
The new data and analyses support the second hypothesis — the idea that Homo floresiensis is an early Homo lineage, likely a sister species of Homo habilis, one of the earliest known species of human found in Africa 1.75 million years ago.
“When we did the analyses there was really clear support for the relationship with Homo habilis. Homo floresiensis occupied a very primitive position on the human evolutionary tree,” said co-author Professor Mike Lee, from Flinders University and the South Australian Museum.
“We can be 99% sure it’s not related to Homo erectus and nearly 100% chance it isn’t a malformed Homo sapiens.”
“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,” added lead author Dr. Debbie Argue, a researcher at the Australian National University’s School of Archaeology & Anthropology.
“It’s possible that Homo floresiensis evolved in Africa and migrated, or the common ancestor moved from Africa then evolved into Homo floresiensis somewhere.”
Where previous research had focused mostly on the skull and lower jaw, this work used 133 data points ranging across the skull, jaws, teeth, arms, legs and shoulders.
“None of the data supported the theory that Homo floresiensis evolved from Homo erectus,” Dr. Argue said.
“We looked at whether Homo floresiensis could be descended from Homo erectus. We found that if you try and link them on the family tree, you get a very unsupported result. All the tests say it doesn’t fit — it’s just not a viable theory.”
“This was supported by the fact that in many features, such as the structure of the jaw, Homo floresiensis was more primitive than Homo erectus.”
“The analyses could also support the theory that Homo floresiensis could have branched off earlier in the timeline, more than 1.75 million years ago,” she said.
“If this was the case Homo floresiensis would have evolved before the earliest Homo habilis, which would make it very archaic indeed.”
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Debbie Argue et al. The affinities of Homo floresiensis based on phylogenetic analyses of cranial, dental, and postcranial characters. Journal of Human Evolution, published online April 21, 2017; doi: 10.1016/j.jhevol.2017.02.006
