Homo floresiensis redated: the long game

The new discovery of further Homo floresiensis remains adds to our body of knowledge while asking as many questions as it answers.

The most significant new information is that floresienses had been on that small island from 700,000 to 55,000 years ago (at the minimum range).

Scientific consensus seems to be that they are a species of Homo.  Although their small stature is suggestive of the Homo predecessor Australopithecus,  it is instead due to insular dwarfism - which means that 700,00 years ago it was already long enough on that small island for it to have evolved smaller to match the scarcity of resources there.

That's an awfully long time to be stuck on an island!  They certainly didn't do much with their time there, compared to the achievements in the span of modern humans.  That indubitably reflects their smaller cranial capacity.

Yet before we disparage a long-static lineage, we need to remember that any such species has to be said to be well-adapted to its environment.  On that basis, they were better adapted than most hominin species, with current evidence showing a lengthier stay on this earth than most others.  That longevity may reflect the stability of the Flores island environment, with little competition from apex predators or other hominin.  Yet it has been said that on available evidence, they disappeared at around the same time modern humans passed through on the way to Australia.  That could be a giant coincidence of the specimens unearthed to date, but it reflects an apparent pattern of Homo sapiens' interaction with other hominin species.

My current questions:

What discussion does this open up about stasis?  There's a lot of possibilities.

Did floresiensis last any longer than 650,000 years?

Were they evolved from Homo erectus?

And in particular, since the original find was entirely due to Mike Morwood seeking an understanding of the migration story of the first Australians, what's the full story of hominin migration between Africa and Australia?  The fossil record suggests there is an awful lot more to be gleaned from digging up all the islands in Indonesia.  Let's hope the past disputes lead to more successful governance of future projects

Dicynodont fossil find is evidence of... what?

How meaningful were media reports (eg  in the UK Telegraph, The Age) in December of a dicynodont fossil find in Tasmania?

The find, dated back to about 250 million years ago, was reported in the Journal of Vertebrate Paleontology, but interested-party scientists and media have a strong interest in making the information a story.  Thus overlaying a slant and significance that the lay person cannot easily navigate.

Dicynodonts (I’m told it’s pronounced dee-, not die-, which does not sound palatable to me, but that probably shows what an amateur I am) were widespread both before and after the great Permian extinction 245 million years ago (which marks the start of the Mesozoic era, typified as the “age of the dinosaurs”).  That event wiped out 80% of animal species and is still subject to debate over cause, although volcanic activity is a popular explanation.

But these animals survived.  They’re not just a single species really, but an infraorder: a group of species one below a class (such as mammals).  They were herbivores, ranging from small to cow-size, the “most successful and abundant land vertebrates of the late Permian” period, according to Wikipedia.

And after an extinction such as the Permian, the various environments are largely depopulated, and ripe for expansion by any species that can survive.  And in fact, after the Permian, a single subset of the dicynodont – the lystrosaurus genus, comprising about five species – truly proliferated throughout the world.  However, the world at the time of the lystrosaurus – and the dicynodont found in Tasmania – was very different – it was one big continent, referred to as Pangea.  Spreading wide would not be a problem at that time – if a species was suitably adaptive to the environment.

So the Tasmania find was not even narrowed down to a species, and it’s not surprising to find it in Tasmania, which was part of Australia until recently, and thus part of Pangea.

In fact, another dicynodont fossil had previously been found in Australia - announced in 2003, after re-examination of a fossil held for decades in Queensland Museum.

Dicynodonts are part of a wider grouping of animals called therapsids, of which only mammals remain.  Yes, all dicynodonts and descendants eventually became extinct.

And despite one of the interested-party scientists (Andrew Rozefelds) saying that the find “fills an important gap in our knowledge of these mammal-like reptiles and where they lived”, I’m still struggling to find what gap it fills.  It’s not to be found in the media.  Alas, access to the Journal of Vertebrate Paleontology is by subscription only.  Maybe if I get to a university library sometime…

References

ABC Science: Ozfossils

Tudge, Colin (2000): The Variety of Life, OUP

Wikipedia: including dicynodont, lystrosaurus, therapsid, permian

some Paleontology sites

A few useful references:

Tet Zoo - Tetrapod Zoology blog. Always something of interest. Somewhat skewed to dinosaurs?

Palaeos - A very good reference for cladograms and geological times

Paleo news - A reasonable summary of recent news, generally stuff that's broken through to mainstream media.

StephenJayGould.org - an "unofficial archive"

Paleoring - for a bit of a trawl

Evolution: rivalry between the sciences

The advancement of evolutionary thought is most definitely a multidisciplinary affair. At its core, it requires an understanding of natural history (paleontology) and genetics - the macro and the micro, if you will.


They're all meant to be united in a detailed understanding of biology, but writings on the subject often betray the specialist's perspective on the other scientists involved in the quest for knowledge.


What I have read sometimes reveals the bias of the particular discipline. If I personally have a bias, it would be towards the sweeping overview of natural history. I find geneticists (such as John Maynard Smith and George C Williams), to paraphrase Mark Twain, all seem to talk about sex but not do anything about it. This apparently places me around the middle rung in the hierarchy.


I think it was Stephen Jay Gould who revealed that a traditional bias of paleontologists was that taxonomists (those essential scientists who analyse similarities and differences between species) are sometimes disparaged as being akin to stamp collectors.


John Maynard Smith in turn revealed that a traditional attitude to paleontologists had been to wish they would "go away and find another fossil, and stop bothering the grownups".
Smith bookended this with context. By way of introduction, he claimed that in the modern synthesis of evolutionary theory that emerged in the 1940s, paleontologists took part, but essentially only to confirm the facts uncovered by "the rest of us", and not to propose any new theory.


This at the beginning of an essay that ultimately praised paleontologists, and Gould in particular for advancing theory in recent times. Then again, Smith admitted to some surprise at the knowledge revealed in the narratives of paleontologists (ably assisted by geologists, climatologists and the like). Genetic analysis is relatively silent on major events such as mass extinctions.


Paleontology is often regarded as being insufficiently hard a science specifically because it often inclines to persuasive narratives, whereas geneticists would have you believe they own the realm of detailed analysis and logic.




Yet the geological and fossil records are thoroughly essential for an understanding of the origins, history and direction of life.





References

Maynard Smith, J (1984): Did Darwin Get It Right? Penguin, London.

Williams, G.C. 1996. Plan and Purpose in Nature. Weidenfeld & Nicolson, London.