What really killed the dinosaurs?
January 26th 2009 04:24
Recently, it has become apparent that the extinction of the dinosaurs was more complex than had previously been envisaged. We thought we had a pretty good handle on the cause of their demise: basically, a gigantic meteorite striking the Earth and releasing the energy of 10 billion Hiroshima bombs, resulting in the extinction of some 65 percent of all species, including the dinosaurs (except birds), pterosaurs and plesiosaurs (contrary to popular misconception, these latter two groups were not part of the Dinosauria, though they were related to them). But nagging questions have cropped up since this supposedly neat explanation was proposed. Why weren't the amphibians wiped out as well? The environmental changes that were thought to have been kicked off by the meteorite, including raging fires and acid rain, should have been at least as devastating to the amphibians as they were to the dinosaurs. After all, amphibians are highly sensitive to chemical perturbations in their habitat. Yet this group, despite suffering somewhat, made it through to the Cenozoic era (the current era), as did many other groups. Is it possible, then, that the meteorite wasn't so much the cause of the dinosaur's extinction as it was the last nail in the coffin for them? There is evidence suggesting that by the late Cretaceous, they were doing rather badly, perhaps owing to widespread climate change. What does seem fairly certain is that, right after the extraterrestrial impact, there was a so-called "fern spike" - a massive increase in the number of ferns, which are good at taking over when other plants have died off. With a lack of plants to eat, the herbivores would have starved, and the carnivores that fed on them would have gone on the same way. It is entirely conceivable that had the impact not occurred the dinosaurs would have eventually gone extinct anyway. But we'll probably never know for sure. Sometimes, groups that are doing badly manage to bounce back (due to fortuitous events that happen to come to their rescue, not destiny). Still, what is clear is that the story of the dinosaurs offers many lessons about natural history, and the more we look, the more complicated and indeed interesting this story becomes.
I highly recommend this absolutely riveting documentary on YouTube. It looks at countervailing arguments about the causes of this mass extinction that occurred 65 million years ago. I've given a summary of the argument that I find most plausible (based upon my admittedly very limited knowledge about this event), but you should judge for yourself. Can anyone think of alternative explanations, consistent with the evidence we have so far, that could explain why the dinosaurs and certain other groups went extinct at the end of the Cretaceous?
(and one final note, if I may. When we talk about something happening at the end of some period or era, we don't mean to imply that there is anything ineluctable about that boundary. The boundary is defined in terms of the interesting event that happened to have occurred. It's not like the aforementioned meteorite struck Earth because it was time to end the Cretaceous; the boundary is defined by that event. It is important to try to rid oneself of the "conceit of hindsight". What happened, happened. It didn't happen in order that something else could happen in the future. In that sense, we - just like all other organisms that live to this day - are accidents, serendipitous products thrown up by the lottery of history's circumstances).
I highly recommend this absolutely riveting documentary on YouTube. It looks at countervailing arguments about the causes of this mass extinction that occurred 65 million years ago. I've given a summary of the argument that I find most plausible (based upon my admittedly very limited knowledge about this event), but you should judge for yourself. Can anyone think of alternative explanations, consistent with the evidence we have so far, that could explain why the dinosaurs and certain other groups went extinct at the end of the Cretaceous?
(and one final note, if I may. When we talk about something happening at the end of some period or era, we don't mean to imply that there is anything ineluctable about that boundary. The boundary is defined in terms of the interesting event that happened to have occurred. It's not like the aforementioned meteorite struck Earth because it was time to end the Cretaceous; the boundary is defined by that event. It is important to try to rid oneself of the "conceit of hindsight". What happened, happened. It didn't happen in order that something else could happen in the future. In that sense, we - just like all other organisms that live to this day - are accidents, serendipitous products thrown up by the lottery of history's circumstances).
| 46 |
| Vote |
