The effects of insular dwarfism and giantism have been well documented in rodents, elephants and artiodactyls, but very little work has been done on other branches of the mammalian family tree.

Before 2003 the effects of the island rule on primates had been largely uninvestigated by the scientific community. In 2003 archaeologists uncovered the remains of a tiny human skeleton reaching only one metre in height, on the island of Flores in Indonesia (Brown et al. 2004). The remains belong to a new species now known as Homo floresiensis dubbed “the hobbit”. Homo floresiensis shares many facial and dental features which link it to larger bodied hominins, and so it has been hypothesised to be a population of south East Asian Homo erectus succumbed to insular dwarfism. Geological evidence shows a volcanic eruption 12,000 years ago was most likely the cause of Homo floresiensis' extinction (Brown et al. 2004). If this is the case then it would make 'the hobbit' the most recent non human hominid to co-exist at the same time with modern humans.

Other examples of reduced size in humans such as the pygmy people of Central Africa are a result of thermoregulatory advantages of being small in a jungle environment (Bromham & Cardillo, 2007). However in these populations cranial facial proportions remain the same, this is not apparent in Homo floresiensis which has a much reduced cranial volume related to its body size when compared to homo erectus. This adds weight to the insular dwarfism hypothesis.

Gene flow between the mainland and the island of Flores occurred between 20,000 and 80,000 years (Brown et al. 2004; Morwood et al. 2005; Bromham & Cardillo, 2007). This may be a sufficient length of time for the dramatic reduction in body size to occur. Geological evidence shows that the island of flores was separated from the mainland long before this which may suggest that Homo erectus had the ability to cross open ocean.

References and Resources