The enigmatic Hobbit is in the news again. About a week ago National Public Radio website which has a pretty solid reputation for good science reporting carried this headline, "Case Grows for 'Hobbit' as Human Ancestor". First some background. Remains of a 3 feet tall human-like creature, technically know as Homo floresiensis, with a brain much smaller than modern humans, were discovered on the island of Flores in Indonesia in 2004. The remains range in age from about 20 -12 thousand years old. Controversy has raged on whether this creature nicknamed the Hobbit represents an extinct species of the human family or whether the remains are of pygmy modern humans (Homo sapiens) with a rare genetic condition known as microcephaly, which causes retardation of brain growth among other body deformities. You can follow the controversy in this series of blogs. The balance of evidence seems to be favoring the hypothesis that Homo floresiensis is a different species of hominid. The latest research dealt with shape of wrist bones, which according to researchers are not at all like the wrist bones in modern humans and Neanderthals, but more like wrist bones in early Homo erectus, the species considered ancestral to modern humans.
So, assuming that the Hobbit is a different species, does that justify a headline calling it a human ancestor? Image below shows the family tree of hominids, showing not only the pattern of branching but also the geographic distribution of the various hominid species.
Note: I just cannot remember where I downloaded this image. If anyone recognizes the source do let me know and I will credit it.
There is still a lot of disagreement on the status of Homo erectus. Some anthropologists call remains of early Homo found in Asia by the species name erectus, preferring the name ergaster for African representatives of early genus Homo. Others prefer naming all early Homo as erectus, a convention I will use here for the purpose of this discussion. What do we make of the early evolution and diversification of Homo erectus? It is convenient to think of erectus as a group of interbreeding populations living in East Africa about 1.2 million years ago. At some point after this date, some members of this population migrated to Indonesia and settled there. Some generations later, some more members of the population in East Africa, left for Europe and settled there. The rest of the population stayed in Africa. The three branches did not have any contact with each other thereafter. Homo floresiensis, Neanderthals and modern humans are the descendants of the populations which settled in Indonesia, Europe and east Africa respectively. That makes Homo floresiensis our distant cousin, not our ancestor.
Why would even experienced science reporting portals such as National Public Radio keep calling the Hobbit as our ancestor? Here are some examples from their article:
"Some scientists have said the Hobbit, found in Indonesia, is a weird human ancestor that somehow survived until some 12,000 to 20,000 years ago....."
"Regardless of whether the Hobbits are our ancestors or simply abnormal humans, they clearly defied steep odds to survive".
I think it has to do with the primitive traits shown by the Hobbit. Primitive traits are those aspects of our morphology or behavior that we inherit from our ancestors and are conserved, i.e. are not changed much. The Hobbit in aspects of its skull morphology and now the shape of wrist bones has retained and conserved traits that it inherited from its early Homo erectus ancestors in east Africa. Some time after the ancestors of the Hobbit had left Africa, evolution changed the shape of the wrist bones in some populations of erectus in Africa. This new wrist bone shape is said to be a derived trait with respect to early Homo. Populations carrying this derived wrist bone shape can be thought of as the common ancestor of the Neanderthals and modern humans. One such population migrated to Europe and evolved into the Neanderthals. Another population evolved into modern humans in Africa.
Hominids who carry ancestral or primitive traits are not necessarily our ancestors. Evolution is a branching process. An ancestral trait may be conserved during evolution in descendants of one branch of the family and modified by evolution in descendants of some other branch. The wrist bones in the human family illustrates this concept very well.