08 May 2917: Update on Homo floresiensis

Since my last blog on Homo floresiensis almost a year ago, two new discoveries have pushed back the origin of the species to at least 700,000 years ago and clarified its line of descent.

The original remains were found in Liang Bua cave on the Indonesian island of Flores in 2004. A short hominin that stood about a metre high, almost inevitably the new species was dubbed the ‘Hobbit’.

H. floresiensis

Homo floresiensis almost certainly not descended from …

There was initial controversy in some corners about whether the remains represented a new species or diseased specimens of Homo sapiens. Mounting evidence that it was indeed a new species climaxed with the announcement in June 2016 that fossils found in the So’a Basin of central Flores in 2014 possess characteristics that are morphologically similar to those found in Liang Bua fossils.

At 700,000 years old, these new fossils are the most ancient hominin remains yet found in Flores, and strongly suggest the ancestors of H. floresiensis first reached the island long before anatomically modern humans had evolved in Africa.

The main debate subsequently shifted to whether or not H. floresiensis was descended from Homo erectus – whose fossils were first discovered in Java – or some other early hominin.

H. erectus

Home erectus, but possibly from …

If descended from H. erectus, the Hobbit was an excellent example of ‘island dwarfism’, where populations of larger animals restricted in geographical range – usually islands – decrease in size over time. (Ironically, smaller animals in the same situation, lacking predators, tend to increase in size.)

A new paper published in the Journal of Human Evolution in April this year, however, presents strong evidence that H. floresiensis most likely descended from an earlier hominin. In the words of the authors, the results of their research indicates it is ‘a long-surviving relict of an early (>1.75 Ma) hominin lineage and a hitherto unknown migration out of Africa … ’

H. habilis

Homo habilis.

Using Bayesian phylogenetic methods and ‘parsimony’, the authors conclude that H. floresiensis is sister either to H. habilis alone or to a clade consisting of other hominin species including H. erectus and H. sapiens. However, they point out that a close phylogenetic relationship between H. floresiensis and H. erectus or H. sapiens can be ruled out.

These findings are important for two reasons.

First, they should finally put paid to any theory that the Hobbits are simply pathological specimens of our own species.

Second, it suggests that our hominin ancestors were migrating from their African homeland long before Home ergaster – the probable ancestor of H. erectus and sister species – decided to emigrate to pastures new some two million years ago.

Wanderlust, it seems, is an essential part of our genetic makeup.

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