A similar conclusion was suggested in a 2018 study dating stone artefacts found at Shangchen, central China, to 2.1 million years ago. DNA extraction attempt In 2006, two teams attempted to extract DNA from a tooth discovered in 2003, but both teams were unsuccessful. It has been suggested that this happened because the dentine was targeted; new research suggests that the cementum has higher concentrations of DNA. Moreover, the heat generated by the high speed of the drill bit may have denatured the DNA. Congenital disorder hypotheses The small brain size of H. floresiensis at 417 cc has prompted hypotheses that the specimens were simply H. sapiens with a birth defect, rather than the result of neurological reorganisation. This theory, however, has been contested, as detailed below. Microcephaly Prior to Jacob's removal of the fossils, American neuroanthropologist Dean Falk and her colleagues performed a CT scan of the LB1 skull and a virtual endocast, and concluded that the brainpan was neither that of a pygmy nor an individual with a malformed skull and brain. In response, American neurologist Jochen Weber and colleagues compared the computer model skull with microcephalic human skulls, and found that the skull size of LB1 falls in the middle of the size range of the human samples, and is not inconsistent with microcephaly. In 2006, American biologist Robert Martin and colleagues also concluded that the skull was probably microcephalic, arguing that the brain is far too small to be a separate dwarf species; he said that, if it were, the 400-cubic-centimeter brain would indicate a creature only in height, one third the length of the discovered skeleton. A 2006 study stated that LB1 probably descended from a pygmy population of modern humans, but herself shows signs of microcephaly, and other specimens from the cave show small stature but not microcephaly. In 2005, the original discoverers of H. floresiensis, after unearthing more specimens, countered that the skeptics had mistakenly attributed the height of H. floresiensis to microcephaly. Falk stated that Martin's assertions were unsubstantiated. In 2006, Australian palaeoanthropologist Debbie Argue and colleagues also concluded that the finds are indeed a new species. In 2007, Falk found that H. floresiensis brains were similar in shape to modern humans, and the frontal and temporal lobes were well-developed, which would not have been the case were they microcephalic. In 2008, Greek palaeontologist George Lyras and colleagues said that LB1 falls