Friday, 29 November 2013

Young-Earth Creationism and Convergent Evidence

A strong scientific theory is supported by the convergence of multiple, independent lines of evidence.  When numerous lines of evidence from different scientific disciplines are in agreement, then their agreed conclusion is strong.  As historians Michael Shermer and Alex Grobman put it:
We know about the past through a convergence of evidence.  Cosmologists use evidence from astronomy, astrophysics, planetary geology, and physics to tell the history of the universe.  Geologists reconstruct the history of the earth through a convergence of evidence from geology and the related earth sciences.  Archaeologists piece together the history of civilization using artwork, written sources, tools and weapons, and other site-specific artifacts. 
The historical theory of evolution gains confirmation by many independent lines of evidence converging on a single conclusion.  Independent sets of data from geology, paleontology, botany, zoology, herpetology, entomology, biogeography, comparative anatomy, physiology, and many other sciences each point to the conclusion that life has evolved.  Creationists demand "just one fossil transitional form" that shows evolution.  But a single fossil cannot prove evolution.  Evolution involves a convergence of fossils and many other lines of evidence, such as DNA sequence comparisons across species.  For creationists to disprove evolution they would need to unravel all these independent lines of evidence and find a rival theory that can explain them better than evolution.[footnote 1]
A conclusion based on multiple sources of evidence can still be very strong even if none of those individual sources of evidence are as strong on their own.  As psychologist Keith Stanovich puts it:
[S]uppose the findings from a number of different experiments were largely consistent in supporting a particular conclusion.  Given the imperfect nature of experiments, we would go on to evaluate the extent and nature of the flaws in these studies.  If all the experiments were flawed in a similar way, this circumstance would undermine confidence in the conclusions....On the other hand, if all the experiments were flawed in different ways, our confidence in the conclusions would be increased because it is less likely that the consistency in the results was due to a contaminating factor that confounded all the experiments....When evidence from a wide range of experiments, each flawed in a somewhat different way or carried out with techniques of differing strengths and weaknesses, points in a similar direction, then the evidence has converged.  A reasonably strong conclusion is justified even though no one experiment was perfectly designed.[2]
Convergent evidence is an important principle to remember when assessing young-Earth creationist criticisms of evolution.  A good case study is the age of the Hawaiian island chain.[3]  Scientists think the chain, which stretches about 3,000 miles (5,000 kilometres) across the Pacific Ocean, was formed by a volcanic 'hotspot': an area where magma periodically breaks the Earth's surface.  As the magma (lava) cools and hardens it forms islands.  The Hawaiian islands are on the Pacific Plate, which is moving to the northwest.  So the islands closest to the hotspot should be the youngest and those that have moved furthest from the hotspot should be much older.

The islands have been dated by potassium-argon dating, which shows the islands have a linear age range that reflects the distance of each island from the hotspot.  The oldest island remnants, at the northern end of the chain, are over 80 million years old.  The youngest island, closest to the hotspot, is less than one million years old.  If you take an island's potassium-argon age and divide it by the island's distance from the hotspot, you can work out that island's movement per year.  Using this method, scientists find the islands are moving at a rate of 2.6-3.6 inches (6.6-9.1 centremetres) per year.

Of course most young-Earth creationists argue radiometric dating such as potassium-argon dating is flawed (see pages 192-3 of The Greatest Hoax on Earth).  Fortunately, there's another way to determine the age of the Hawaiian island chain.  Scientists can use Global Positioning Systems to measure the rate the islands are moving.  These measurements give a movement of approximately 3.1 inches (7.9 centimetres) per year, which happens to be exactly in the middle of the rate of movement calculated by potassium-argon dating.  Assuming the islands have always moved at this rate, scientists can work out how old the islands are based on how far they are from the hotspot.

Of course young-Earth creationists would question the assumption that the islands have moved at the same rate in the past.  Fortunately, there's another source of evidence supporting the age of the Hawaiian islands.  Volcanic islands gradually subside and erode as they age: height and activity are both thought to peak when the volcano is around 500,000 years old, then they decline as the volcano (which becomes dormant and eventually extinct) is slowly eroded over millions of years.  Thus, in Hawaii, the newest islands should be the tallest ones and they should be closest to the hotspot.  And that is the case: as you move northwest along the island chain, away from the hotspot, you find the islands decrease in elevation and show an increase in weathering and erosion.

Of course young-Earth creationists would dispute a timeframe of millions of years for the erosion of the islands.  Fortunately, there's yet another means of dating the islands.  Ancient coral reefs form terraces off the shore of many of the Hawaiian islands.  Scientists can use radiometric dating (such as uranium-thorium dating) to determine the age of the coral.  Of course, as noted already, young-Earth creationists reject radiometric dating.  Fortunately, the coral is useful in other ways.  First, the coral reefs reinforce the evidence based on the elevation and erosion of the islands.  If the islands formed over millions of years, then the oldest islands should not only be more eroded, they should also have much larger and thicker coral reefs – which is the case.  Second:
Both modern corals and fossil corals deposit daily and annual growth bands. By careful analysis of these bands, we can tell how many days there were in a year when the coral was growing. For modern corals, this technique yields 365 day-bands per year, more or less, just as it should. For corals that grew in formations identified as Early Devonian [around 400 million years ago], the technique shows a little over 400 day-bands per year.  Astronomers can measure the rate at which Earth's rotation is slowing. Assuming the rate of slowing has remained constant, a day-count of 400 days per year indicates an age of roughly 400 million years. And when Early Devonian rocks are dated radiometrically, we get dates of roughly 400 million years.[4]
Thus the radiometric evidence and the biological and astronomical evidence provide similar dates.  Of course young-Earth creationists also dispute the reliability of these types of evidence (though they appear to rely on literature from over 30 years ago to do so).[5]

The example of the Hawaiian island chain shows that young-Earth creationists have to reject an awful lot of evidence from multiple, independent sources.  The problem for young-Earth creationists is that all of these lines of evidence support the same conclusion: the Hawaiian islands were formed over millions of years.  Further lines of evidence (such as those from evolutionary biology and biogeography[6]) not summarised here also support this conclusion.  Additionally, other island chains on the Pacific Plate thought to have been formed by hotspots have the same patterns of movement and of radiometric ages as the Hawaiian islands.[7] 

The counter-argument from young-Earth creationists is that much of the explanation for the how the Hawaiian island chain was formed is hypothesis, rather than confirmed fact.  For example, even the 'secular' literature disputes the precise location and form of the Hawaiian hotspot and there is evidence it has moved at certain points in the past.[8]  The few young-Earth creationist articles addressing the Hawaiian island chain seize upon such examples in an attempt to discredit the millions-of-years timeframe.[9]  However, these young-Earth articles fail to address the principle of converging evidence: scientists may disagree over specific aspects of how the Hawaiian island chain was formed, but all the evidence still points to the chain having been formed over millions of years.  Young-Earth theories (like catastrophic plate tectonics) fail to account for all the independent lines of evidence, which conclude the Hawaiian island chain was formed over millions of years and not in a matter of days during Noah’s flood.


References:

[1] Michael Shermer and Alex Grobman, Denying History: Who Says the Holocaust Never Happened and Why Do They Say It?, Berkeley: University of California Press (2000), p 32.

[2] Keith Stanovich, How To Think Straight About Psychology, Boston: Allyn & Bacon (2004, seventh edition), p 128.

[3] In this discussion I use the term ‘island chain’ loosely – it also includes seamounts: underwater mountains that rise above the ocean floor but don’t break the surface of the water (effectively underwater islands). My description of the Hawaiian island chain draws on the following sources: Robert Tilling, Christina Heliker, and Donald Swanson, ‘Plate Tectonics and the Hawaiian Hot Spot’ (2010) http://geology.com/usgs/hawaiian-hot-spot/; Hawaiian Volcano Obervatory, 'Evolution of Hawaiian Volcanoes' (1995) http://hvo.wr.usgs.gov/volcanowatch/archive/1995/95_09_08.html; Ken Rubin, 'The Formation of the Hawaiian Islands' (2005) http://www.soest.hawaii.edu/GG/HCV/haw_formation.html; Steve Olson, Evolution in Hawaii: A Supplement to Teaching About Evolution and the Nature of Science, Washington, DC: The National Academies Press (2004), pp 5-9; Monterey Bay Aquarium Research Institute, 'Hawaiian Coral Reefs' (2012) http://www.mbari.org/volcanism/Hawaii/HR-CoralReefs.htm

[4] Jonathon Woolf, 'An Introduction to Radiometric Dating' http://www.jwoolfden.com/rad_dat.html; see also: Normal Newell, Creation and Evolution: Myth or Reality, Westport: Greenwood Press 1984, pp 119-24.

[5] See, for example: Shaun Doyle and Tas Walker, 'BioLogos and the age of the earth: Pushing an anti-biblical doctrine' (4 October 2012) http://creation.com/biologos-age-earth

[6] See, for example: C Barry Cox and Peter Moore, Biogeography: An Ecological and Evolutionary Approach, Hoboken: John Wiley & Sons (2010, eighth edition), pp 231-238; Warren Wagner and Vicki Funk (eds), Hawaiian Biogeography: Evolution on a Hot Spot Archipelago, Washington, DC: Smithsonian Institution Press (1995).

[7] Patrick Nunn, Pacific Island Landscapes, Suva: The University of the South Pacific (1998), pp 161-3; Daniele Buigues, 'Geology and Hydrogeology of Mururoa and Fangataufa, French Polynesia', in H L Vacher and T Quinn (eds), Geology and Hydrogeology of Carbonate Islands, Oxford: Elsevier Ltd (1997), pp 433-5.

[8] On location and form, see: Qin Cao, et al, ‘Seismic Imaging of Transition Zone Discontinuities Suggests Hot Mantle West of Hawaii’, Science, Vol 332, No 6033 (2011), pp 1068–1071, online: http://www.sciencemag.org/content/332/6033/1068.full; on past movement, see: Caroline Uhlik, 'The 'fixed' hotspot that formed Hawaii may not be stationary, scientists conclude', Stanford Report (8 January 2003) http://news.stanford.edu/news/2003/january8/aguhotspots-18.html

[9] Tas Walker, 'The Hawaiian hot spot and the Bible' (28 May 2011) http://creation.com/hawaii-hot-spot; Tas Walker, 'The elusive Hawaiian hot spot spoils a nice geological story' (4 June 2011) http://biblicalgeology.net/blog/elusive-hawaiian-hot-spot/

2 comments:

  1. I'll flag your article in a live discussion with a US YEC named Robert under John Heininger's review of 'Hoax' at Amazon.com. Another Christian there, Jon, was a YEC after reading Sarfati's book but then gradually became unconvinced of that view (but still a keen Christian which is fine by me).

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  2. For information:
    http://forums.bcseweb.org.uk/viewtopic.php?f=1&t=3418

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