The Mini Dinosaurs from the Harz Mountains

FiReaNGeL writes "When unusually small dinosaur fossils were found in a quarry on the northern edge of the Harz Mountains in 1998, it was initially assumed that these were the remains of a group of young dinosaurs. This was a fallacy, as the Bonn palaeontologist, Dr. Martin Sander, recently discovered. At a maximum estimated weight of one tonne, they were only a fiftieth the weight of their closest relatives, the brachiosaurs, and thus by far the smallest of the giant dinosaurs which have ever been found."

Re:Mini-people

[afaik_ianal]

This may fit in elegantly, but last I heard (maybe even on slashdot) this discovery was now believed to be a normal human with a disease of some sort.

It's still disputed. Wikipedia has a short summary of the 2 opinions here: http://en.wikipedia.org/wiki/Homo_floresiensis#A_n ew_species.3F [wikipedia.org]

The thing I don't understand about the hypothesis that the fossil is actually a diseased human, is that they found partial fossils of 8 other individuals, which I assume were consistent with the near-complete fossil being debated. What are the chances of them all having this extremely rare defect, given that it shortens life expectancy, and severely limits normal brain function?

It's hotly contested.

[jd]

Near the site of the "hobbits", they have found fairly advanced stone tools and stone arrowheads. People so acutely affected by the suggested dwarfing disorder would have inhibited brain function and certainly could not have developed an advanced technology or operated it. This makes it somewhere between unlikely to impossible for all of the people on the island to have been mentally afflicted. This leaves only two options - either these remains are of extremely unusual people, and were in a community of more typical hominids, and it's pure chance that no remains of these typical hominids have been found, OR they genuinely were a miniaturized subcategory of hominid that were not impaired at all, so there is no contradiction involved with there being an advanced technology.

The debate has likely intensified even further with recent genetic studies of Neanderthals, using mtDNA extracted from the teeth. This is because the mtDNA shows vastly greater variation in early Neanderthal genetic makeup than had ever been expected. So much so that all prior studies are now considered grossly inadequate, as they only examined a hundred or so base pairs, considering the rest to be essentially identical. If genetic diversity in early hominids in general was as great as genetic diversity in early Neanderthals is believed to have been, then the probability of there having been a natural experiment in hobbits is considerably greater.

There is, however, one outstanding problem that has NOT been resolved. Dwarfism on islands is common with reptiles. Reptiles do NOT do islands well. However, mammals on islands tend towards giantism - Amblyrhiza Inundata (a giant rat the size of a grizzly) being an excellent example. Birds, although descended from reptiles, also seem to do well on islands - the Moa (a flightless bird that was 13 feet tall) and the Haast Eagle (the largest eagle that ever lived, with a wingspan of 14 feet), both from New Zealand, being good examples. This is because mammals scale well and therefore lose very little by being large, even when resources are scarce. Reptiles don't scale so well, so there is a loss of efficiency in being large. No big deal on a large enough land mass, but on an island, it's a major problem.

Humans, because they are potentially much better at cooperating, are capable of planning and storing, and are able to access a much wider range of foods over a much greater range of environments, should (based on knowledge of other island-based mammals) scale up on islands extremely well, and should only shrink where conflict is greatest, which would typically be a continent. It's hard to say if this is the case, as humans have always been amazingly mobile, but my gut feeling is that you'll find more very tall people on or around islands than you will in the middle of continents. This creates a problem for the hobbits, though. Mammals shrink when being able to run is a far greater survival trait than being able to gather more. On an island, there is very little to run from and almost nowhere to run to. There should, therefore, be no advantage to them being that small and therefore no reason for such a trait to be selected.

I think it likely that the hobbits are indeed a new branch of hominids, but without a good, solid explanation for why they would be small, the theory will never be acceptable to any evolutionary scientist worth a damn, no matter how much they want it to be true, simply because it runs counter to what we know about mammals on islands. Answering that one question will probably quell a lot of the more skeptical scientists, too. A mechanism that ties things together and presents a coherent picture is more acceptable than an extrapolation, no matter how many fossils it is from.