Although the diminutive Homo floresiensis has been known for a decade, its phylogenetic
status remains highly contentious. A broad range of potential explanations for the
evolution of this species has been explored. One view is that H. floresiensis is 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. Fossil remains of H. erectus, well known from Java, have not yet been
discovered on Flores. The second hypothesis is that H. floresiensis is directly descended
from an early Homo lineage with roots in Africa, such as Homo habilis; the third is
that it is Homo sapiens with pathology. We use parsimony and Bayesian phylogenetic
methods to test these hypotheses. Our phylogenetic data build upon those characters
previously presented in support of these hypotheses by broadening the range of traits
to include the crania, mandibles, dentition, and postcrania of Homo and Australopithecus.
The new data and analyses support the hypothesis that H. floresiensis is an early
Homo lineage: H. floresiensis is sister either to H. habilis alone or to a clade consisting
of at least H. habilis, H. erectus, Homo ergaster, and H. sapiens. A close phylogenetic
relationship between H. floresiensis and H. erectus or H. sapiens can be rejected;
furthermore, most of the traits separating H. floresiensis from H. sapiens are not
readily attributable to pathology (e.g., Down syndrome). The results suggest H. floresiensis
is a long-surviving relict of an early (>1.75 Ma) hominin lineage and a hitherto unknown
migration out of Africa, and not a recent derivative of either H. erectus or H. sapiens.