Homo floresiensis extinct by 50,000 years ago
A new study published in Nature has suggested that Homo floresiensis became extinct much earlier than originally reported. The type specimen LB 1, recovered from Late Pleistocene sediments at Liang Bua, Flores in 2004 was claimed to be 18,000 years old, with other remains and associated stone tools dating from 74,000 to 95,000 years old. The dates were inferred from radiocarbon, thermoluminescence, uranium series and electron spin resonance dates on associated sedimentary material. No direct dates were obtained from the remains themselves for fear of damaging them. However, some authorities were dubious that the ‘hobbits’ could have survived for so long after modern humans reached Southeast Asia.
It has now been discovered that the hominin remains and artefacts were found in a stratigraphic sequence of older sediment forming a pedestal, which have been truncated by one or more phases of erosion and subsequently covered by later sediment. This was not recognised during the original excavations, hence making the accuracy of the inferred dates suspect.
The new dates have been obtained by dating the main stratigraphic units within the pedestal; and this time direct dating was also applied to the skeletal remains of Homo floresiensis. Radiocarbon, thermoluminescence, and uranium series methods were used. The revised dates suggest that the skeletal remains range from 60,000 to 100,000 years old and the associated stone tools range from 50,000 to 190,000 years old.
Parts of Southeast Asia may have been inhabited by Denisovans during this period, and modern humans reached Australia by 50,000 years ago. Whether either came into contact with Homo floresiensis or were connected to its demise is at this stage still unknown.
Sutikna, T. et al., Revised stratigraphy and chronology for Homo floresiensis at Liang Bua in Indonesia. Nature, doi:10.1038/nature17179 (2016).
Study confirms that Flores hominins are not Homo sapiens
Since their headline-making discovery in 2003, the diminutive hominins from the Indonesian island of Flores have been generally accepted to be a distinctive human species, Homo floresiensis. Popularly referred to as ‘hobbits’, they are widely believed that they owe their small size to a phenomenon known as ‘insular dwarfism’. In the absence of dangerous predators and in a habitat where food is scarce, it was suggested that they ‘downsized’ from their ancestral condition as evolution favoured smaller, less ‘gas-guzzling’ individuals. The ancestral species is often claimed to be Homo erectus, but claims have also been made for more primitive hominins such as Homo habilis or even Australopithecus.
Not everybody accepted that Homo floresiensis was a new human species and among the sceptics was the late Teuku Jacob, an Indonesian anthropologist who claimed that the ‘hobbits’ were modern humans affected by a developmental disorder known as microcephaly. Some years after Jacob’s death, his former colleagues revived the theory, this time claiming that Homo floresiensis were modern humans suffering from Down syndrome.
A newly-published study describes the investigation of the cranial bones of the partial female skeleton LB 1 (popularly and perhaps inevitably known as ‘Flo’). A series of high-resolution scans were taken using an X-ray CT scanner. Comparative scans were also taken of microcephalic specimens used in earlier studies of LB 1. The scans were used to study the bone thickness distribution of the cranial vault and internal bone composition and structure. Cranial vault thickness (CVT) can be diagnostic of a hominin species attribution, and it was found to be thick for LB 1 in absolute terms and even more so in relative terms when the small cranial size is taken into account. By contrast, microcephalic skulls of modern humans are thinner than those of humans unaffected by the condition. It was found that Flo had suffered from a condition known as bilateral hyperostosis frontalis interna, and bore the healed scar of a head injury, but there was nothing to indicate that she had suffered from any developmental disorders of the type suggested by Jacob or his former colleagues.
The researchers showed that LB 1 displays characteristics related to the distribution of bone thickness and arrangements of cranial structures that are primitive traits for hominins, differing from the derived condition of modern humans. This was not seen with the microcephalic skulls.
The study thus rules out the possibility that LB 1 can be assigned to Homo sapiens, but leaves the issue of its true affinities unresolved.
Balzeau, A. & Charlier, P., What do cranial bones of LB1 tell us about Homo floresiensis? Journal of Human Evolution 93, 12-24 (2016).
Dental study rejects modern human or earlier hominin connection with Homo floresiensis
The origin of the diminutive ‘hobbits’ of Flores, Indonesia have been controversial since they were announced as a new human species, Homo floresiensis, in 2003. The most widely accepted view is that they are descended from a group of Homo erectus that reached Flores at least a million years ago and underwent a phenomenon known as insular dwarfism whereby a combination of low risk of predators and a relative scarcity of food means that smaller individuals are favoured from an evolutionary point of view and thus individuals within a population will ‘downsize’ over the course of many generations.
However, there are two alternative viewpoints. The first is that the Homo floresiensis remains simply represent modern humans affected by a condition such as microcephaly or cretinism. The second view accepts that the Flores hominins are indeed descended from an archaic species, but posit that it is something more primitive than Homo erectus – possibly Homo habilis or an australopithecine. It is argued that the absence of fossil evidence for such early hominins leaving Africa is not evidence of absence from Eurasia.
In a newly-published study, researchers carried out extensive comparisons using linear metric analyses, crown contour analyses, and other trait-by-trait morphological comparisons of the molar, premolar and canine teeth of Homo floresiensis against an extensive sample of teeth from present-day modern, prehistoric modern, and archaic humans. Three methods were used: metric analyses based on crown length and breadth data; comparisons of crown contour using normalized Elliptic Fourier Analysis (EFA); and non-metric and linear metric comparisons of individual morphological traits not recorded by the first two methods.
The researchers found suggest that the Homo floresiensis teeth do share derived characteristics with those of Early Pleistocene Homo erectus from East Africa and Java, and with the Dmanisi hominins from Georgia; but none of the ‘hobbit’ teeth exhibit the very primitive morphology associated with Homo habilis or australopithecines. Such characteristics include the occasional absence of a P3 buccal groove, a distally positioned P3 lingual cusp, a more circular P4 crown, the presence of a P4 transverse crest, non-parallelogram M2 crown shape, a mesiodistal short M2 crown, a M1 mid-trigonid crest, equivalent M1 and M2 sizes, and a moderately wide upper dental arcade. The findings rule out the claim that Homo floresiensis evolved from a hominin that was more primitive than Homo erectus.
Nor was a good match found with the modern samples. In comparison to Homo floresiensis, the teeth of Homo sapiens are derived for nine out of 26 character states, contradicting the suggestion that the dentition of Homo floresiensis is wholly modern.
Overall, the results suggest that Homo erectus is the ancestral species; however the dentition of Homo floresiensis did continue to evolve and possesses some unique features not seen in any other hominin species. These include the large (relative) size and the unique occlusal morphology of the P3 that otherwise exhibits primitive morphologies; and the extremely short first molars. In view of the general trend of molar shortening during the evolution of Homo over time, this condition in Homo floresiensis is actually more derived than in Homo sapiens.
It must be assumed that these evolutionary changes reflected the unique habitat of Flores, but regardless they demonstrate the distinctiveness of Homo floresiensis as a species.
Kaifu, Y. et al., Unique Dental Morphology of Homo floresiensis and Its Evolutionary Implications. PLoS One 10 (11) (2015).
New papers revive ‘hobbit’ controversy
The announcement in 2003 that dwarf hominins had been discovered at Liang Bua Cave on the Indonesian island of Flores was one of the major news stories of that year. The type specimen, LB1, a female inevitably dubbed ‘Flo’ had lived had lived just 18,000 years ago at a time when all archaic hominins were believed to be long extinct. Estimated to have been around thirty years old at the time of her death, ‘Flo’ stood just 1.06 m (3 ft. 6 in.) tall, weighed 16 and 36 kg (35 and 79 lb), and had an estimated cranial capacity of just 380 cc, comparable to that of an australopithecine.
Rapidly dubbed the ‘hobbit people’ on the grounds of their diminutive stature, the hominins were recognised as a new human species, Homo floresiensis. It was suggested that in the absence of natural enemies on an island where food is fairly scarce, ‘Flo’s’ people had undergone a process known as insular dwarfism, where smaller individuals are positively selected for and over several generations, the entire population ‘downsizes’.
Not everybody accepted this explanation. In 2006, the late Teuku Jacob claimed that Flo was a modern human of Australomelanesian extraction, who had suffered from a developmental disorder leading to a smaller brain known as microcephaly. Jacob found little support for his views and was also criticised for allegedly damaging the specimens while they were on loan to him from the Indonesian National Archaeological Research Center.
The controversy had been revived by the publication of two companion papers in the journal PNAS. Two of the authors of these new papers were also involved with Jacob’s original study. The first paper, Henneberg, et al (2014), argues that Flo was suffering from Down syndrome. This can result in atavism, where developmental characteristics of an earlier ancestral condition appear alongside undisrupted characteristics. This pattern could explain what has been otherwise interpreted as a mosaic of primitive and derived features. As a teratological specimen, the authors note that LB1 is not eligible to be designated the type specimen of a new species.
In the second paper, Eckhardt, et al (2014) suggest that based on an examination of the Flores specimens made in 2005, both the stature and brain size of LB1 have been underestimated. LB1, they argue, possessed abnormalities such as craniofacial asymmetry and a thigh bone disproportionately short in relation to its other long bones. Such abnormalities are indicative of Down syndrome and a number of other developmental conditions.
1. Jacob, T. et al., Pygmoid Australomelanesian Homo sapiens skeletal remains from Liang Bua, Flores: Population affinities and pathological abnormalities. PNAS 103 (36), 13421–13426 (2006).
2. Henneberg, M., Eckhardt, R., Chavanaves, S. & Hsüc, K., Evolved developmental homeostasis disturbed in LB1 from Flores, Indonesia, denotes Down syndrome and not diagnostic traits of the invalid species Homo floresiensis. PNAS (Early Edition) (2014).
3. Eckhardt, R., Henneberg, M., Weller, A. & Hsüc, K., Rare events in earth history include the LB1 human skeleton from Flores, Indonesia, as a developmental singularity, not a unique taxon. PNAS (Early Edition) (2014).
Links (all papers are open access):
Jacob, et al http://www.pnas.org/content/103/36/13421.short
Henneberg, et al http://www.pnas.org/content/early/2014/07/31/1407382111.abstract
Eckhardt, et al http://www.pnas.org/content/early/2014/07/31/1407385111.abstract
Did ‘hobbit people’ of Flores evolve from Homo erectus or a more primitive hominin?
Homo floresiensis is an extinct Late Pleistocene hominin species known only from the Indonesian island of Flores. The type specimen LB 1 is a diminutive 30-year-old female who stood just 1.06 m (3 ft. 6 in.) tall. Nicknamed ‘Flo’, she had a cranial capacity initially estimated to be just 380 cc, comparable to that of an australopithecine. Her weight was estimated to be somewhere between 16 and 36 kg (35 and 79 lb.). Yet she was apparently human: she lacked the large back teeth of an australopithecine, the proportions of her facial skeleton were those of a human, and she appeared to be a humanlike fully-committed biped (Brown, et al., 2004; Morwood, et al., 2004).
The extremely small cranial capacity has been hotly debated since the species was first described in 2004. Some have claimed that Flo was a modern human suffering from microcephaly, a developmental disorder leading to a smaller brain (Jacob, et al., 2006; Martin, et al., 2006), but the majority reject this view and recognise Homo floresiensis as a new human species with a long, low cranial vault and other features characteristic of archaic humans (Argue, et al., 2006; Falk, et al., 2005; Falk, et al., 2007; Tocheri, et al., 2007; Lyras, et al., 2008).
Two principle theories have emerged as to the origin of these hominins. The first is that Homo floresiensis was a dwarf form of Homo erectus (approximate cranial capacity 1,000 cc) which underwent a dramatic reduction in size as a result of a phenomenon known as insular dwarfism. Animals living on an island where food is relatively scarce and predators are few or absent will ‘downsize’ over many generations, in order to reduce calorific requirements. What is actually happening is that evolution is favouring the smaller offspring in each generation. If predators do not pose a threat, any advantages in being large will be outweighed by poorer fuel-economy. What has to be questioned is whether insular dwarfism could lead to brain size reduction of the extent seen in Homo floresiensis.
The second theory is that Homo floresiensis is derived from a hominin species more primitive and smaller-brained than Homo erectus such as Homo habilis (approximate cranial capacity 600 cc) or even an australopithecine (approximate cranial capacity 400 cc). This second model implies that Homo erectus was not the first hominin species to leave Africa, contrary to the widely-accepted Out of Africa 1 hypothesis.
Two studies, one published in 2010 and the other earlier this year, have focussed on decreases in brain size. The first study considered the decreases in body mass and brain size that have been documented for a number of other primate lineages. Researchers tested putative ancestors for Homo floresiensis against these, using the high, medium and low estimates of its body mass. Results suggested that Homo erectus is only feasible as an ancestor for Homo floresiensis if the low estimate of 16 kg (35 lb.) is accepted. For the medium estimate of 24 kg (53 lb.), Homo habilis or the Dmanisi hominins are more feasible as ancestors. The high estimate is not compatible with any proposed scenario (Montgomery, et al., 2010).
The second study re-evaluated the brain size of Homo floresiensis using micro-CT scanning, and obtained an upwardly-revised estimate of 425 cc. This revised figure means that the degree of brain size reduction in relation to body mass is less, and therefore easier to explain. Nevertheless, if Homo erectus was the ancestor, the decrease in brain size is still too great to be explicable solely as a scaling downwards as body mass is downsized, and some other factor must have come into play. In an environment where food is scarce, and given that brain tissue is ‘expensive’ in metabolic terms, further reduction in brain size might have been advantageous. However, this could not be achieved without some loss of cognitive ability. The authors of the report suggested that cognitive abilities comparable to Homo habilis might have sufficed in an island habitat lacking dangerous predators (Kubo, et al., 2013).
While this ‘dumbing down’ scenario cannot be dismissed, it seems implausible. According to the widely-accepted ‘social brain hypothesis’ (Byrne & Whiten, 1988), the large primates of primates evolved in response to a need to predict the likely future social behaviour of their fellows, and base relationships upon these predictions. While Homo floresiensis would not have had to face dangerous predators, individuals would still need to interact with other group members. It is difficult to see that being less smart than one’s fellows could be anything over than a severe disadvantage, regardless of other circumstances.
I would therefore be inclined to the view that Homo erectus was not the ancestor of Homo floresiensis, and this view is supported by a number of studies considering the skeletal evidence. These have noted that while the cranial metrics were consistent with Homo erectus, the limb proportions of Homo floresiensis had more in common with Australopithecus garhi (Argue, et al., 2006) and the feet were a mosaic of primitive apelike and derived humanlike features. The big toe was fully in-line, albeit short, and the metatarsals followed a humanlike sequence in which the 1st (innermost) was the most robust (sturdily-built), followed by the 5th (outermost), then 4th, 3rd, and finally 2nd. The foot, though, was disproportionately long in comparison to that of a modern human; the lesser metatarsals (2nd to 5th) were long; and the outer toes were long and curved, unlike the short, straight toes of a modern human (Jungers, et al., 2009). The fact that the feet and limb proportions of Homo erectus were modern suggests that Homo floresiensis evolved from a species that was more primitive, such as Homo habilis.
1. Brown, P. et al., A new small-bodied hominin from the Late Pleistocene of Flores, Indonesia. Nature 431, 1055-1061 (2004).
2. Morwood, M. et al., Archaeology and age of a new hominin from Flores in eastern Indonesia. Nature 431, 1087-1091 (2004).
3. Jacob, T. et al., Pygmoid Australomelanesian Homo sapiens skeletal remains from Liang Bua, Flores: Population affinities and pathological abnormalities. PNAS 103 (36), 13421–13426 (2006).
4. Martin, R. et al., Comment on ‘‘The Brain of LB1, Homo floresiensis’’. Science 312, 999b (2006).
5. Argue, D., Donlon, D., Groves, C. & Wright, R., Homo floresiensis: Microcephalic, pygmoid, Australopithecus, or Homo? Journal of Human Evolution 51, 360-374 (2006).
6. Falk, D. et al., The Brain of LB1, Homo floresiensis. Science 308, 624-628 (2005).
7. Falk, D. et al., Brain shape in human microcephalics and Homo floresiensis. PNAS 104 (7), 2513–2518 (2007).
8. Tocheri, M. et al., The Primitive Wrist of Homo floresiensis and Its Implications for Hominin Evolution. Science 317, 1743-1745 (2007).
9. Lyras, G., Dermitzakis, M., Van der Geer, A., Van der Geer, S. & De Vos, J., The origin of Homo floresiensis and its relation to evolutionary processes under isolation. Anthropological Science (2008).
10. Montgomery, S., Capellini, I., Barton, R. & Mundy, N., Reconstructing the ups and downs of primate brain evolution: implications for adaptive hypotheses and Homo floresiensis. BMC Biology 8 (9), 1-19 (2010).
11. Kubo, D., Kono, R. & Kaifu, Y., Brain size of Homo floresiensis and its evolutionary implications. Proceedings of the Royal Society B 280 (1760) (2013).
12. Byrne, R. & Whiten, A., Machiavellian Intelligence (Oxford University Press, Oxford, 1988).
13. Jungers, W. et al., The foot of Homo floresiensis. Nature 459, 81-84 (2009).
Homo floresiensis is the name given to a possible human species that lived on the Indonesian island of Flores. One largely complete skeleton (LB1) and a complete mandible (LB2) were found in sediment in the Liang Bua Cave in eastern Flores, in 2003 (Brown et al, 2004). The material, dated at 18,000 years old, was not fossilised or covered with calcium carbonate, but was extremely fragile. The discoverers, a team led by anthropologists Peter Brown and Michael Morwood, recovered further material including a second mandible and postcranial material from other individuals, in 2004. In total, the finds represented at least nine individuals. Stone tools were also found, dating to 95,000-75000 years old and 12,000 years old. These comprised high densities of stone cores, flaking debris, retouched tools and anvils, evidencing a flaking technology comparable to that found at African Oldowan and other Lower Palaeolithic sites. The tools were accompanied by faunal remains, indicating that the area was a focus for a range of hominin activities (Morwood et al, 2005; Tocheri et al, 2007).
LB1 was claimed to have been a 30-year-old female. The cranial capacity of LB1 is 380cc and its stature is no more than 3ft6 (106cm), both of which are comparable to or smaller than Australopithecus afarensis (“Lucy”). The discoverers argued, however, that it possessed a variety of both primitive and derived features, and should be placed in genus Homo:
“When considered as a whole, the cranial and postcranial skeleton of LB1 combines a mosaic of primitive, unique and derived features not recorded for any other hominin. Although LB1 has the small endocranial volume and stature evident in early australopithecines, it does not have the great postcanine tooth size, deep and prognathic facial skeleton, and masticatory adaptations common to members of this genus. Instead, the facial and dental proportions, postcranial anatomy consistent with human-like obligate bipedalism and a masticatory apparatus most similar in relative size and function to modern humans all support assignment to the genus Homo—as does the inferred phylogenetic history, which includes endemic dwarfing of H. erectus. For these reasons, we argue that LB1 is best placed in this genus and have named it accordingly.” (Brown et al, 2004).
The diminutive size of Homo floresiensis was, the team claimed, a result of a phenomenon known as insular dwarfism, where animals living on an island where food is relatively scarce and predators are few or absent will “downsize” over many generations in order to reduce calorific requirements. This is of course no more than evolution favouring the smaller offspring in each generation. If predators do not pose a threat, any advantages in being large will be outweighed by poorer fuel-economy. Before Mesolithic humans reached Flores, the island met both conditions in being both relatively faunally-impoverished and lacking any predators other than the Komodo dragon. If early humans such as Homo erectus had reached Flores, then the same thing could have happened, leading to H. floresiensis.
The team claimed that despite its tiny ape-like brain, the encephalization quotient (EQ) or brain to mass ratio was in the range 2.5 to 4.6, compared with 5.8 to 8.1 for modern humans, 3.3 to 4.4 for Homo erectus/ergaster and 3.6 to 4.3 for Homo habilis. The figure was derived from an estimated brain mass of 433.2gm (based on cranial volume) and two estimates of body mass: an estimate based on stature of 106cm gave 16.0-28.7kg; one based on femur cross-sectional area of 525mm2 gave 36kg.
The EQ is a better indication of intelligence than absolute brain size; for example, elephants and whales have larger brains than humans, but are generally considered to be less intelligent than the latter. The team claimed the higher figure of 4.6 was supported by the probability that Homo floresiensis would have the same lean, narrow body shape as a modern Old World tropical-dwelling human. Thus H. floresiensis was capable of complex behaviour and cognition, and was probably the maker of the tools. Oldowan-equivalent technology would be well within its capabilities.
The discovery attracted considerable publicity, and Homo floresiensis was immediately nicknamed the Flores Hobbit, to Brown’s considerable annoyance (quoted in the Observer, 31 October 2004). However doubts as to whether it was genuinely a new human species emerged almost immediately.
The Indonesian anthropologist Prof. Teuku Jacob claimed that LB1 was a modern human suffering from microcephaly, a developmental disorder leading to a smaller brain. Jacob claimed LB1 was a male Homo sapiens aged 25-30 of Australomelanesian extraction.
An unpleasant dispute then followed when, in December 2004, Jacob removed most of the remains from the Jakarta’s National Research Centre of Archaeology, where they had been placed for safekeeping, without permission of this institution’s directors. Jacob was widely cited in press reports as having a reputation for preventing access to specimens in his keeping and Brown was quoted in the New Zealand Herald as saying he doubted “if the material will ever be studied again”.
Jacob eventually did return the remains, but the discoverers claimed the bones were extensively damaged in Jacob’s lab during attempts to make casts. The alleged damage included long, deep cuts marking the lower edge of the LB1’s jaw on both sides, said to be caused by a knife used to cut away the rubber mould. In addition, LB2 was snapped and glued back together. Whoever was responsible misaligned the pieces and put them at an incorrect angle. The pelvis of LB1 was smashed, destroying details that reveal body shape, gait and evolutionary history. Morwood accused Jacob of being greedy and acting irresponsibly. Jacob denied any wrongdoing and published his own findings contra Brown et al in July 2006 (Jacob et al, 2006). Teuku Jacob died in October 2007, aged 77, but his death did not put an end to the controversy.
Although primatologist Robert Martin of the Field Museum, Chicago, IL supported Jacob’s position (Martin et al, 2006), the majority of workers rejected the microcephaly theory and accepted Homo floresiensis as a new human species (e.g. Argue et al, 2006; Falk et al, 2005 & 2007; Lyras et al, 2008 and Tocheri et al, 2007) .
The studies mainly focussed on the cranial and post-cranial metrics of LB1 in comparison to microcephalic humans, pygmies, early human species (Homo erectus, H. ergaster, H. habilis, etc) and australopithecines (A. garhi, A. africanus, P. bosei, etc.). The general conclusion was that H. floresiensis showed a better fit with the various extinct hominins than it did with the microcephalic or normal modern humans, though the studies differed as to its likely phylogeny, with affinities to Homo erectus, Homo habilis and even the later australopithecines all being proposed. LB1’s long low cranial vault is not a feature shared with modern humans, microcephalic or not (Lyras et al, 2008); LB1’s wrist morphology, based on three wrist bones, predates that of modern humans (Tocheri et al, 2007). Other pathological explanations such as Laron syndrome and cretinism were also rejected (Lyras et al, 2008).
Falk et al (2005) noted expansions in the frontal polar region of LB1. This part of the prefrontal cortex in humans and apes consists of Brodmann’s area 10 (BA10), which in humans may be involved in higher cognitive processes such as the undertaking of initiatives and the planning of future activities. The Falk study concluded that LB1’s brain could not have been a miniaturized version of Homo sapiens or H. erectus.
Citing this study, Argue et al (2006) suggested the implication is that LB1 possessed developed cognitive abilities and was able to plan, respond to conditions, use memories, and transfer information between group members.
Brumm et al (2006) considered 880,000 year old artefacts recovered from the Mata Menge site at the Soa Basin, central Flores in comparison to the Liang Bua artefacts and suggested the two show technological continuity. They suggest the hominins responsible for the Liang Bua artefacts were also responsible for those at Mata Menge, though no hominin remains have been recovered from the latter site.
What are we to make of all this? The case for Homo floresiensis being a pathological modern human does not strike me as being very convincing and on the balance of probabilities I would cautiously accept that it is indeed a new species of hominin. Obviously further evidence, in particular evidence that can be tied to the earlier tool finds, would be highly desirable.
Could H. floresiensis be an intermediate between early Homo and late Australopithecus that migrated out of Africa prior to 2 million years ago (Argue et al, 2006)? It’s not impossible that enhanced cognitive function evolved more than once, in Homo habilis and its descendants and in Homo floresiensis (though the latter would have to be transferred to a new genus to avoid paraphyly should this hypothesis become accepted). Nor would it be impossible for such a hominin to diffuse from Africa, given that the ancestors of the orang-utans did millions of years earlier. The main problem is there is absolutely no other evidence supporting dispersal from Africa of any australopithecine species or of Homo habilis, or of anything intermediate between the two. Homo georgicus, the small-brained hominin from Dmanisi, Georgia, has been touted as evidence Homo habilis did migrate from Africa, but it has now been shown to have a derived Homo ergaster (African Homo erectus) body plan.
Early Homo erectus, or something of that grade seems a more plausible ancestor. The tool technology is consistent with that of the first H. erectus dispersal from Africa, which seems to have happened before the invention of the later Mode II Acheulian hand-axe tradition. The cognitive abilities of Homo floresiensis were probably commensurate with such technology, which predates the emergence of modern human behaviour. As such, therefore, H. floresiensis would have lacked the complex language of modern humans, though it probably had language of sorts.
The question of how the forbears of these people reached Flores in the first place has led some to speculate that they must had the ability to build boats, since Flores – unlike many islands in the Indonesian archipelago – was never connected to the mainland, even during the maximum extent of the ices ages, when sea-levels dropped. But they could have been swept out to sea and stranded there by a natural occurrence such as a flash-flood or a tsunami, possibly on a raft of matted vegetation. This is believed to have been the way the ancestors of the New World monkeys reached South America from Africa; nobody is suggesting that they built boats!
Probably the most controversial idea is that Homo floresiensis survived into modern times and is the mythological Ebu Gogo said to have been living on Flores when the Portuguese arrived 400 years ago, and some claim were still being seen as recently as 100 years ago; and that similar people are the basis of similar legends such as the Orang Pendek from Sumatra and even leprechauns in Ireland?
I will admit to being sceptical (decidedly so about leprechauns!), if only because “little people” are so prevalent in world folk traditions that if these were due to actual diminutive hominins, concrete evidence would have emerged by now. However if an endemic dwarf hominin species can arise on Flores, there is certainly no reason to suppose similar species could not arise elsewhere and it is quite possible that evidence from similar genetically-isolated locations might come to light in the future.
Debbie Argue, Denise Donlon, Colin Groves, Richard Wright (2006): Homo floresiensis: Microcephalic, pygmoid, Australopithecus, or Homo? Journal of Human Evolution 51 (2006) 360-374.
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© Christopher Seddon 2009