The Rise and Fall of Dinosaurs

April 11, 2005

Having recently covered a plethora of social and political topics, my thoughts have turned to the rise and fall of dinosaurs, prompted by by an article in Discover magazine. One of the “unanswered questions” they presented was How did the dinosaurs get so big? And the answer they proposed was that for some reason there was a huge increase in CO2 causing runaway plant growth and therefore making vast amounts of food available. While I can't say that's wrong, it feels wrong. It supposes a sudden change in the composition of the atmosphere, which lasted for millions of years, ended suddenly, and didn't leave fossil evidence that there was a corresponding increase in the size or number of other herbivores.

It also doesn't address the issue of of why plant growth didn't quickly bring the level of CO2 back down to a lower level, or where all the carbon went. While some source of millions of years of CO2 is possible, it requires a release mechanism which provides enough CO2 for plant growth without removing so much oxygen from the atmosphere thet the animals notice a lack. And given that dinosaurs were both large and fast, it's hard to believe that there was a lack of oxygen. I think that rules out release and burning of methane.

Let me make a wild speculation here, justified by only in that it doesn't contradict any facts known to me, and that it seems to require less speculation about causes than any “suddenly all the plants got bigger” hypothesis. While a mutation causing giantism is not impossible, even one which is dominant rather than recessive, postulating that it happened in all the reptiles at the same time requires more assumption that I wish to believe.

To grow, an animal requires more nourishment for both mass and energy. But the increase could come not from a large increase in volume, but a from large increase in digestive efficiency instead. Consider for a moment the humble bacteria. The human gut is full of them, and they help digestion. Anyone who has had a course of strong antibiotic will tell you that the lack of such bacteria will cause significant changes in the digestive function, and not for the better.

If there evolved such a bacteria, and it lived and flourished in the gut of reptiles, and it allowed more efficient use of the same volume of food, and doesn't require changes in the atmosphere or contagious mutations. It assumes that the bacteria could pass through the gut, be transmitted to all similar species, and affect only a subset of animals, the dinosaurs, which had the correct intestinal conditions and diet to benefit from such a bacterium. It also provides a possible answer to questions of why other, non-reptile, herbivores didn't suddenly increase in size.

At the end of the dinosaur era, you can speculate on an extinction caused by meteor impact, methane bubbling, or evolution of a mold which killed the bacteria. We at least have recent evidence that the last of these could happen, Penicillin is indeed a mold. So while the killer mold theory is speculation, there is proof that such a mold could evolve, and assuming that it did so in the forage of the large dinosaurs, a spread to the smaller herbivores and by ingestion to the carnivores is at least “not impossible” as a mechanism of deployment.

So there you have it, my take on the creation and destruction of the dinosaurs, by means of natural nanotechnology. It avoids the need for sudden evolution and cosmic events, which William of Occam would probably claim made it the most likely explanation.