New evidence for Island Dwarfism with implications for Homo floresiensis

18 April 2007 (Daily Telegraph and Biology Letters) – Thanks to Liz Price for flagging me to this piece of news, a new study published in the Royal Society journal Biology Letters demonstrates that primates conform to the theory of “Island Dwarfism”. Island Dwarfism describes the phenomenon that in areas where resources are limited (eg, islands), small animals become larger and large animals become smaller in a bid to be more efficient in gathering food. The study can be found in this week’s Biology Letters, which a subscription-based. The abstract is published here:

Primates follow the ‘island rule’: implications for interpreting Homo floresiensis
Lindell Bromham and Marcel Cardillo

When the diminutive skeleton of Homo floresiensis was found on the Indonesian island of Flores, it was interpreted as an island dwarf, conforming to the ‘island rule’ that large animals evolve smaller size on islands, but small animals tend to get larger. However, previous studies of the island rule have not included primates, so the extent to which insular primate populations undergo size change was unknown. We use a comparative database of 39 independently derived island endemic primate species and subspecies to demonstrate that primates do conform to the island rule: small-bodied primates tend to get larger on islands, and large-bodied primates get smaller. Furthermore, larger species undergo a proportionally greater reduction in size on islands.

The Daily Telegraph, which I assume has access to the article, expounds on the connection with Homo Floresiensis further and makes careful mention that the article does not imply the genus of our beloved hobbit, whether it was Homo sapiens or Homo erectus.

Hobbit hominids lived the island life

…

Lindell Bromham and Marcel Cardillo trawled through published journals and online databases to see how primates performed when subjected to the “island rule”.

True enough, small primate species (ones weighing less than 5kg) all pumped up compared to their mainland relatives – but all the larger primates became smaller, in a range of between 52 and 80 per cent.

That fits in well with H. floresiensis, who was around 55 per cent of the mass of a modern Indonesian and probably 52 percent of an H. erectus.

So the evidence backs the idea that the hobbits were an insular dwarf race – humans who became smaller, possibly after the island separated from the mainland and left them marooned with diminished food resources.

The authors refuse, though, to wade into the debate as to whether the hobbits were H. erectus or H. sapiens.

Also unclear is why the hominids had a relatively undersized brain compared to their diminutive body. A modern human child of the same size has a much larger brain, as do pygmies.

So the hobbits may well be products of their own environment, but the question as to what species they are remain unanswered for another day…

Related Books:
– Little People And a Lost World: An Anthropological Mystery by L. Goldenberg