Extinction hypotheses

Much - indeed, most - of what has been proposed to explain the extinction of dinosaurs does not even possess the basic prerequisites for a viable, scientific theory. These minimal criteria are:

1. The hypothesis must be testable. As we have seen (see Chapter 3), for a hypothesis to be considered in a scientific context, it must be testable; that is, it must have predictable, observable consequences. Without testability, there is no way to falsify a hypothesis and, in the absence of falsifiability, we

Fort Union - 0

Hell Creek (m)

Fort Union - 0

Figure 15.15. Sudden extinction of the dinosaurs. The vertical axis shows meters through the Hell Creek Formation, the uppermost unit in the Western Interior of the USA. "0" is the K/T boundary. The horizontal axis shows various vertebrate groups (including dinosaurs) that are found within the Hell Creek. Virtually all vertebrate groups are present throughout the thickness of the Hell Creek; there is no gradual decrease in the groups as the boundary is approached. The data indicate that the extinction of the dinosaurs and other vertebrates at 65.5 Ma was geologically instantaneous.

Figure 15.15. Sudden extinction of the dinosaurs. The vertical axis shows meters through the Hell Creek Formation, the uppermost unit in the Western Interior of the USA. "0" is the K/T boundary. The horizontal axis shows various vertebrate groups (including dinosaurs) that are found within the Hell Creek. Virtually all vertebrate groups are present throughout the thickness of the Hell Creek; there is no gradual decrease in the groups as the boundary is approached. The data indicate that the extinction of the dinosaurs and other vertebrates at 65.5 Ma was geologically instantaneous.

are then considering belief systems rather than scientific hypotheses. If an event occurred and left no traces that could be observed (by whatever means available), science is simply not an appropriate tool to investigate the event.

2. The hypothesis must be parsimonious; that is, explain all the events in question. This criterion is rooted in the principle of parsimony (again, see Chapter 3). We

K/T Boundary 65.0

K/T Boundary 65.0

Figure 15.16. Sudden extinction of the dinosaurs in intermontane basin sedimentary deposits of the Late Cretaceous of the U.S. Western Interior, as demonstrated by Lillegraven and Eberle (1999). The vertical axis shows meters through the K/T Ferris Formation and time (Ma). The horizontal axis shows various vertebrate groups (including dinosaurs) that were found in the study. Virtually all vertebrate groups are present below the boundary; there is no gradual decrease in the groups as the boundary is approached. After the boundary, diversity is drastically reduced. The data indicate that the extinction of the dinosaurs and other vertebrates 65.5 Ma was geologically instantaneous.

would like to explain an event or series of events. If each step of the event (or events) requires an additional ad hoc explanation, our hypotheses lose strength. They are strongest when the most parsimonious explanation is used: that explanation which explains the most observations. For this reason, if we can explain all that we observe at the K/T boundary with a single hypothesis, we have produced the most parsimonious hypothesis and it has a good chance of being correct.

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