Flores is a small island in the Indonesian archipelago between Java and Timor. The remains encountered include a skull in very good condition and part of the skeleton, including the pelvis. They were found along with various remains of extinct fauna such as pigmy elephants and gigantic lizards. The age of the remains is also surprising: 18,000 years, which implies that they were humans which co-existed with our species. The human remains found on Flores are attributed to a human species (Homo floresiensis) distinct from us, and which very possibly evolved from Homo erectus.
The pelvis suggests that it must have been a woman, and the obvious wear on the teeth implies that she must have died at an adult age. Thus, her small stature corresponds to a specific characteristic and not to a short life.
Why was she so small?
When a population of large-sized herbivores becomes geographically isolated in a small area where food is short, the only way to survive is by reducing their size. Thus, for example, on Sicily, elephants managed to reduce their weight to only 250 kg. (550 lbs.). So, after a time this population evolves, giving rise to a new species, which, although a direct descendant, is now distinct from the parent species.
According to Brown, this evolutionary mechanism is the one which must have allowed Homo floresiensis to arise. An ancestral population of Homo erectus could have arrived by boat, which would have been a feat of its own, on the island of Flores. There, it would have remained isolated and would have evolved until it gave rise to these diminutive human beings, nicknamed "hobbits".
From what species did it arise?
How did these humans get as far as Flores? If they really evolved from Homo erectus, did they do so before arriving on Flores, or, did erectus colonize the island and then evolve to this new human species? According to the discoverers, the latter is the more plausible hypothesis in order to explain its diminutive size. But this implies that erectus was capable of travelling by boat more than 750,000 years ago.
The human remains most closely related to those of Flores are logically to be found on the island of Java. Here, remains of Homo erectus have been found which might be as much as 1.8 million years old. The colonization of most of the present Indonesian archipelago would not have been especially difficult for these humans because at that time it would have been united to Malaysia, forming the Peninsula of Sonda.
But populating Flores is another matter. Ever since humans have existed, this territory has always been an island, separated from Sonda by very deep waters, waters which nowadays are very rough and have strong currents. So much so that when, in 1968, Verhoeven discovered stone instruments some 750,000 years old on Flores associated with the remains of extinct elephants, the scientific community could not but be surprised. Had Homo erectus indeed been capable of sailing over such dangerous waters?
If Homo erectus built boats and sailed to the island, which was located over the horizon, and thus out of sight, there is no doubt that we have to attribute to him truly significant cognitive capacities.
Human intelligence with the brain size of chimpanzee?
The technology constitutes another piece of the puzzle. Associated with Homo floresiensis are thousands of stone instruments, many of them as much as 75,000 years old. These instruments present some technical characteristics similar to those fabricated by sapiens and neanderthalensis of the same time period. And these latter species were equipped with brains three or four times the volume of the brain of floresiensis.
What was the origin of the technology of Homo floresiensis? Did they inherit it from Homo erectus? Were they capable of inventing it with such a small brain? This is one of the most controversial points of the discovery of Brown and Morwood.
How is it possible for a human being to be intelligent with such a tiny brain? Most of the australopithic craniums discovered to date have a more voluminous brain than this human woman. Nevertheless, Homo floresiensis must have been intelligent since it manufactured tools.
In recent years the paleoanthropologist Leslie C. Aiello has popularised the thesis that we became humans thanks to the consumption of meat. This thesis includes two basic hypotheses: (a) the increase in brain size is due to the contribution from proteins derived from the ingestion of meat, and (b) intelligence emerged when a certain level of encephalization was reached. Both hypotheses are hotly contested.
Concerning the first hypothesis, Stephen Oppenheimer, a specialist in genetics and human evolution, wonders "why should our brains have grown, and not those of the other mammals living at the edge of the savannah?" (1). He goes on to say that "without evidence, all such arguments for the role of climate and meat-eating in the enhanced brain growth of early humans remain largely armchair speculation".
With regard to the second hypothesis, it seems reasonable to think that intelligence has something to do with the notable size of our brain (notable, that is, in proportion to the volume of our body). Nevertheless, there is more and more evidence that the brain of the various examples of our own Homo sapiens species was once larger than it is now. All indications are, in fact, that a steady reduction of the human brain size has been taking place, without a corresponding decrease in body size. So, the size of the human brain has experienced a progressive decrease over the same time period in which the most outstanding advances in human culture have taken place..
The discovery of Homo floresiensis complicates this much more. How is it possible that a human species with a brain of only 380 cm3 is capable of fabricating tools as complicated as those attributed to Homo floresiensis? If floresiensis is truly a human species distinct from ours, the history of human evolution in the last 100,000 years will have to be re-written.
Carlos A. Marmelada is a teacher and science journalist from Spain. Translated by Joe Atkinson.
(1) Nature, Vol. 431, pp. 1055-1061 & 1087-1091, 2004.
(2) Stephen Oppenheimer, Out of Eden: The Peopling of the World, Constable, 2003, pp. 9-10.