Monday 4 November 2013

Chapter 10: Biogeography and Remote Islands

On pages 165-175 of The Greatest Hoax on Earth Sarfati discusses biogeography (the study of the distribution of animals and plants around the world today and in the past).  He focuses on 'remote' islands (Australia, Madagascar and the Galapagos) in an attempt to refute the biogeographical evidence for evolution.

Australian marsupials

Sarfati first focuses on the predominance of marsupials in present-day Australia.  On pages 169-70 he lists several problems with the evolutionary explanation for how the vast majority of modern marsupial species came to be in Australia:
  • the fossil record suggests marsupials once lived in Eurasia and North America before they lived in Australia, but marsupials are now largely absent from Eurasia and North America
  • some modern marsupials are found in Papua New Guinea and Indonesia[bullet]a Chilean marsupial (Dromiciops gliroides) is more closely related to some Australian marsupials (such as the brushtail possum, Trichosurus vulpecula) than it is to other South American marsupials
  • a fossil platypus tooth was found in South America
  • a 120-million-year-old placental fossil was found in Australia.
Sarfati doesn't actually outline the evolutionary explanation for Australia's marsupials.  Perhaps he expects his readers to have also read Dawkins' The Greatest Show on Earth.  Or, more likely, he knows most of his readers are young-Earth creationists who aren't interested in evolutionary explanations beyond being told what is wrong with them.

The current evolutionary explanation for the origin of Australia's marsupials addresses all but the last of Sarfati's 'problems'.  Marsupial fossils are found in Eurasia and North America because marsupials are thought to have first evolved in the northern continents and then spread into South America around 70-60 million years ago.  In South America marsupials underwent adaptive radiation (basically evolved into many different species) and some species continued spreading to Antarctica (which was connected to South America until around 30 million years ago, and had a very different climate) and on to Australia (which was connected to Antarctica until around 45-35 million years ago).[footnote 1]  That explains the platypus fossil in South America and the link between Chile's Dromiciops gliroides and Australia's marsupials.[2]

Modern marsupials are thought to have reached the islands north of Australia (such as New Guinea and Sulawesi) relatively recently – around 19,000 years ago sea levels fell enough that New Guinea was joined with the Australian landmass, and it remained so for 10,000 years.[3]

So for some reason Sarfati gives examples that largely support the evolutionary view.  A better line of attack for young-Earth creationists would be to highlight some of the significant gaps in the marsupial fossil record: the fossil record for Asia and Europe is poor; the few marsupial fossils found in Antarctica resemble those from South America but not those from Australia; and there is a gap of around 30 million years in the fossil record for Australian marsupials.[4]  Sarfati hints at such problems on page 169 when he quotes Cifelli and Davis on the difficulties in matching modern marsupial distribution with the fossil record.[5]

Sarfati's final point on marsupials – the 120-million-year-old placental fossil – is an interesting one.  There isn't agreement that the fossil, Ausktribosphenos nyktos, actually is a placental mammal.  It may instead have been a monotreme, or belonged to its own extinct lineage of eutherian mammals.[6]  Perhaps Sarfati could have made more of this, but then nobody yet knows enough about Ausktribosphenos.

Madagascan lemurs and Galápagos iguanas

Sarfati also provides brief discussions of Madagascar's lemurs and the Galápagos Islands' iguanas.  On lemurs, he criticises Dawkins' mischaracterisation of the young-Earth creationist view, which is fair enough.  And he points out the evolutionary explanation for how lemurs got to Madagascar – floating across from Africa on rafts of vegetation – is rather far-fetched (indeed, it sounds more like a young-Earth creationist explanation: see Sarfati's comment in footnote 19 on page 172).  However, it's worth noting the rafting explanation seems slightly less outlandish when considered in light of recent research into the ocean currents between African and Madagascar around 60 million years ago.[7]

On pages 171-2 Sarfati quotes Dawkins at length, simply to point out that Dawkins is incorrect in his statement that the marine and land iguanas of the Galápagos Islands cannot interbreed.  Here Sarfati has got it right.  Dawkins is wrong:
It is interesting that, despite their long separation time, the marine and land iguanas are still capable of hybridizing and producing viable offspring.  A morphologically unusual iguana was reported from the island Plaza Sur.  Molecular analyses confirmed the hybrid status of this individual and revealed that it was the offspring of a male marine and female land iguana.  As yet, however, hybridization has been reported only from this island and does not seem to play an important role in the evolution of the local iguana populations.[8]

References:

[1] Michael Archer and John Kirsch, 'The evolution and classification of marsupials', in Patricia Armati et al (eds), Marsupials, Cambridge University Press (2006), p 19.

[2] For more on Dromiciops gliroides see: Maria Nilsson, et al, 'Tracking Marsupial Evolution Using Archaic Genomic Retroposon Insertions', PLoS Biology (Public Library of Science), Vol 8, No 7 (2010) http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2910653/

[3] Thomas Heinsohn, 'Marsupials as introduced species: long-term anthropogenic expansion of the marsupial frontier and its implications for zoogeographic interpretation', in Simon Haberle, et al (eds), Altered Ecologies: Fire, Climate and Human Influences on Terrestrial Landscapes, Canberra: ANU Press (2010), pp 138, 159-67; available online at: http://epress.anu.edu.au/wp-content/uploads/2011/02/ch0911.pdf

[4] See: Archer and Kirsch, p 18, and Verity Bennett, 'Fossil Focus: Marsupial evolution - a limited story?', Palaeontology Online, Vol 2, Article 10 (2012) http://www.palaeontologyonline.com/articles/2012/fossil-focus-marsupials/

[5] Their article is worth reading beyond Sarfati's heavily ellipsed quote. See: Richard Cifelli and Brian Davis, 'Marsupial Origins', Science, Vol 302, No 5652 (12 December 2003), pp 1899-1900; available online at: ftp://ftp.soest.hawaii.edu/engels/Stanley/Textbook_update/Science_302/Cifelli-03.pdf

[6] Chris Johnson, Australia's Mammal Extinctions: A 50,000 Year History, Cambridge University Press (2006), pp 4-5; available online at: http://assets.cambridge.org/97805218/49180/excerpt/9780521849180_excerpt.pdf

[7] See: Jason Ali and Matthew Huber, 'Mammalian biodiversity on Madagascar controlled by ocean currents', Nature, Vol 463, Issue 7281 (2010) pp 653-6; partly available online at: http://www.readcube.com/articles/10.1038/nature08706

[8] Kornelia Rassmann, et al, 'Tracing the Evolution of the Galápagos Iguanas: A Molecular Approach', Iguanas: Biology and Conservation, University of California Press (2004), pp 76-7.

8 comments:

  1. I haven't studied the above in depth but appears to be a fair and balanced survey of the relevant issues.

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  2. Re Australasian mammals. A comment that creationists can't answer (mainly because there is no stock answer for them to cut and paste).

    Why, when there is such an abundant radiation of feral mammals in New Zealand today, are there no native terrestrial mammals from New Zealand? Why would God have denied mammals this green and pleasant land, in which they clearly survive today when introduced by humans?

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  3. Thanks for the comments. As someone who lives in New Zealand (which is also Sarfati's land of birth), I have a particular interest in NZ's fauna!

    I haven't found any young-Earth creationist attempts to explain NZ's wildlife, but I imagine their answer to Christine's question would be a rambling (and likely contradictory) discussion about:

    - land bridges (there weren't land bridges to NZ for non-flying mammals to cross on their way from the Ark)
    - ocean currents and geographic distance (mammals couldn't get to NZ on rafts because the currents after the Flood didn't flow that way and/or NZ is too far from anywhere for a raft to reach it)
    - the fossil record (mammals could have reached NZ after the Flood but have since died out - just because no one's found mammal fossils, doesn't mean mammals weren't once here)
    - problems in evolutionary explanations (there's disagreement amongst mainstream scientists over exactly why NZ doesn't have terrestrial mammals, therefore young-Earth creationsim must be true)
    - the limits of human knowledge (we can never know the answer to every problem, but we do know we should trust in [a fundamentalist/literal interpretation of] God's word).

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    1. "- land bridges (there weren't land bridges to NZ for non-flying mammals to cross on their way from the Ark)"

      So how did the tuatara get there? (And multiple other non-mammalian terrestrial animals, inc. flightless birds.) (Yes I know some of the debates about the birds, but the creationists don't!)

      "- ocean currents and geographic distance (mammals couldn't get to NZ on rafts because the currents after the Flood didn't flow that way and/or NZ is too far from anywhere for a raft to reach it)"

      Ditto

      "- the fossil record (mammals could have reached NZ after the Flood but have since died out - just because no one's found mammal fossils, doesn't mean mammals weren't once here)"

      But we have a gazillion fossils of moas. So if there were mammals there, we'd find them (just like we do in Australia).

      "- problems in evolutionary explanations (there's disagreement amongst mainstream scientists over exactly why NZ doesn't have terrestrial mammals, therefore young-Earth creationsim must be true)""

      There's no disagreement whatsoever among scientists.

      Hmm. Either they don't know about this conundrum, or they do know and are keeping quiet about it. Either way, it's an excellent one to stump a creationist with, because there is no pat answer for them to cut and paste on their favorite websites.

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    2. Ha. Well I never said young-Earth creationist explanations for New Zealand's fauna would be good ones!

      "So how did the tuatara get there? (And multiple other non-mammalian terrestrial animals)"

      That's a good point. I have to admit that I hadn't even thought of New Zealand's reptiles, frogs and many flightless invertebrates. The fact that they made it all the way to New Zealand from the Ark, but mammals for some reason did not, poses an even greater challenge to young-Earth explanations. Perhaps Noah asked the birds to carry them here....

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  4. Also, interestingly, New Zealand may have had terrestrial mammals in the past -

    In 2006 some scientists found a few fossil bones of a mouse-sized mammal in NZ, dated to 16-19 million years ago.

    See:
    http://www.newscientist.com/article/dn10773-fossils-reveal-new-zealands-indigenous-mouse.html
    http://www.pnas.org/content/103/51/19419.full

    But a few other articles at the time mention that some paleontologists didn't think the bones provided enough evidence to confirm the hypothesis that they were from a land-based mammal. And there doesn't seem to have been much follow-up after the initial discovery.

    See also:
    https://groups.google.com/forum/#!msg/sci.bio.paleontology/Ej_lIjo1dLw/jQXEXT0vxf8J

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    Replies
    1. Yes, I know about it. The people who discovered it (Mike Archer & Sue Hand) are colleagues of mine, and they have now determined that it's actually a bat. I don't know if they have published a retraction!

      BTW, thanks for reposting my reply to Sarfati on Australopithecus. I had a good one on Tiktaalik, too!

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    2. Thanks for the update on the mysterious mammalian fossil!

      And thanks for posting your reply to Sarfati on Australopithecus in the first place. I find it invaluable when I come across an academic commenting within their field of expertise on the bits of Sarfati's book that blunder into that field.

      I will go and track down your comments on Tiktaalik.

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