Evolutionary Implications

The discovery of Homo floresiensis has had significant implications for our understanding of human evolution.

The unique morphological features of Homo floresiensis, including its diminutive stature and small brain size, demonstrates a new range of biological diversity in the genus Homo. Many recent studies have supported the hypothesis that Homo floresiensis represents a distinct hominin species. As such, determining the ancestry of Homo floresiensis is critical as it can shed light on the evolutionary history responsible for the unique blend of anatomical features seen in Homo floresiensis.

Based on cranial and dental morphologies, researchers have suggested early African or Asian Homo erectus was the ancestral population of Homo floresiensis. Given the larger body mass and brain size of Homo erectus, this evolutionary scenario would imply a substantial decrease in body and brain size in the Homo floresiensis population, perhaps as an outcome of dwarfing in an isolated, insular environment.

On the other hand, some mandibular (jaw bone) and postcranial characteristics of Homo floresiensis, such as limb proportions and foot morphologies, exhibit similarities with early Homo (e.g. Homo habilis) and even members of the Australopithecus genus. In this second scenario, the small body and brain size of Homo floresiensis are not as surprising, given the smaller stature of these early hominins. However, this scenario also implies that there was an (as-yet-unknown) dispersal of early hominins out of Africa prior to the spread of Homo erectus about 1.8 million years ago.

Another evolutionary implication of Homo floresiensis is that, because of deep neighbouring straits, the island of Flores has been isolated by sea even during glacial periods when sea levels were much lower. Homo floresiensis or its ancestors must, therefore, have arrived on the island after making a sea-crossing. Some researchers have suggested that Early and Middle Pleistocene hominins may have possessed sea-crossing capabilities, but it is certainly possible that hominins were washed on to the island by chance, as a result of tsunami or storm events.

The recently revised chronology for Homo floresiensis also has important implications for understanding the relationship between an extinct hominin group and early modern humans, and their possible interaction. The revised extinction dates for Homo floresiensis at Liang Bua are about 50, 000 — 60, 000 years ago, which coincides with the time of arrival of modern humans in Sahul (the continent that comprises mainland Australia, Tasmania, New Guinea and the neighbouring islands). Parts of Southeast Asia could have also been inhabited by other hominin groups, such as the Denisovans, at this time. Whether or not Homo floresiensis survived after 50, 000 years ago, and if they encountered modern humans or other hominin groups on Flores, remain open questions. The revised chronology raises the possibility that the arrival of modern humans in the region played a role in the eventual disappearance of Homo floresiensis. Similar hypotheses have been proposed for the extinction of the Neanderthals in Europe, soon after the arrival of modern humans around 45, 000 years ago. Whether modern humans contributed to the demise of the Neanderthals through direct conflict or via competition for resources are lingering questions that researchers are currently investigating.