Tuesday, November 19, 2013

Amber implies low oxygen levels for the dinosaurs

A specimen of amber, found in Alberta, Canada, containing
leaves from an extinct conifer.  It is thought to be 77 million
years old.  Credit: Ryan C. McKellar.  Image source.
One of the fascinating aspects of dinosaurs is the immense size that some of them attained.  Though not quite reaching the mass of the modern blue whale, dinosaurs certainly seemed to be the largest land animals that ever lived, exceeding the size of elephants several times over.  Supplying such massive bodies with sufficient oxygen would have been quite a feat, requiring extremely strong hearts and lungs, especially given the small size of their nostrils.  Both creationist and evolutionist scientists propose that the job was made easier for the dinosaurs by higher oxygen concentrations in the atmosphere at the time they were alive.  Some studies have estimated that the atmosphere in the Cretaceous period was 30% oxygen, compared to today's 21%.

Last week, an international team of scientists published a study analyzing resin and amber for clues to past oxygen levels (original article available for purchase).  According to their conclusions, oxygen levels at the time of the dinosaurs were actually significantly lower than today, challenging the prevailing assumptions.

Resin is the sticky substance secreted by coniferous trees (not to be confused with sap, which transports nutrients through the trees).  If resin is buried quickly enough and isolated from weathering and biological processes, it will eventually harden into amber, which is often used as a gemstone due to its rich, dark, golden color.  As anyone who has watched Jurassic Park will know, amber often contains other biological material, ranging from leaves to insects, nearly perfectly preserved.  However, this study is concerned not with the preserved contents of the amber, but with the amber itself.

The scientists used measurements of carbon-13 (13C) to infer the atmospheric oxygen levels at the time the former resin was produced by a tree.  This process should not be confused with carbon-14 dating, which uses decay rates of carbon-14 to infer age.  Carbon-13 is not radioactive, but it is slightly heavier than its more common isotope, carbon-12 (12C).  Because of this weight difference, 13C is slightly less likely to move around in an ecosystem than 12C.  Therefore, plants that absorb carbon from atmospheric carbon dioxide will have a slightly lower proportion of 13C than the atmosphere. The ratio of plant 13C to atmospheric 13C is consistent according to the type of plant, and it can be measured in modern ecosystems.  Curiously, the authors of the study claim that the amount of 13C in resins is more indicative of oxygen levels than of atmospheric 13C levels.  The high amounts of 13C in amber samples, according to the authors, demonstrate that oxygen levels were as low as 10% (compared to today's 21%) during the Mesozoic (the time of the dinosaurs).

This study presents some amount of difficulty for both evolutionists and creationists.  As I mentioned earlier, both camps propose high oxygen levels to account for the great size of the dinosaurs and other extinct creatures.  It is difficult to imagine how such large creatures survived in such oxygen-depleted environments, particularly for millions of years in the evolutionary timeline.  The authors propose that volcanic eruptions added excessive carbon dioxide to the atmosphere, diluting the oxygen, but this explanation does nothing to help the evolutionary model.  It may, however, explain the results in a creation model.

Although layers in which the amber is buried are attributed to the Flood by creationists, the actual production of the resin must have occurred immediately before the Flood.  I have no data on the lifespan of resin, but I think it is safe to assume that the resin was produced within a year before it was buried.  If the volcanic explanation is accurate, it may suggest that there was a period of high volcanic activity during the year prior to the Flood itself, possibly related to the beginnings of tectonic movement.  The oxygen levels may have been high enough before then to support gigantic life for many generations, and a few months of lower oxygen levels should not have been enough to wipe out the dinosaurs before they were brought to Noah.  Juvenile dinosaurs were likely taken aboard the Ark as representatives of their kinds, so it would not matter if the largest ones died of oxygen deprivation during the pre-Flood volcanic year.

Of course, it is always possible that the study itself is in error.  The authors recommend further investigation, indicating that the results are not final.  Despite the authors' claims to the contrary, it may be that the plants which produced the ambers are not quite the same as their modern counterparts, producing different 13C/12C ratios during photosynthesis.  Their claims that 13C are related to oxygen levels may also be in error. Unfortunately, I do not have access to the full article, so I am currently unable to investigate their claims further.

Aside from oxygen levels, amber and resins provide fascinating glimpses into past life and plenty of uses for us today.  Even frankincense and myrrh, two of the gifts given to baby Jesus, are made from resin!  Although I doubt that we will ever be able to clone dinosaurs from mosquitoes trapped in amber Jurassic Park style, I have no qualms with continued study of these substances and the biological bits contained within them.

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