Introduction Extinction, a case of two perspectives.
Extinction is studied by paleontologists, paleoecologists and by neontologists (biologists who study living organisms). Both groups bring a very different perspective to the discussion, and both suffer from significant problems due to the very nature of their field of study. Paleontologists and paleoecologists study ancient animals and ecosystems, most of which are already extinct. Neontologists on the other hand are basically in the midst of the game, since life goes on all around them. Let me illustrate the differences with some analogies.
Paleoecology interpreting the graveyard.
In a sense, the paleontologist is surrounded by results (of evolution, environmental changes on the earth, possibly catastrophes) but must interpret the cause.
Imagine two investigators who are attempting to decipher the history of a small town by studying the local graveyard. Its an odd town, because the tombstones simply list the decade in which the person died, not the actual date (e.g., John Doe, died 1870s).
Our investigators begin by collecting all of the data available in terms of the number of tombstones dated per decade. Investigator 1 tabulates the data and produces the following table:
At first glance it appears fairly obvious that the 1870s were anomalous for the very large number of deaths which occurred during that decade. The average death rate (what we might refer to as the "backround death rate") is an average of 8.5 per decade. So, with a death rate during the 1870s of approximately ten times backround, something happened but what?
Investigator 2 has been talking to some local people, and has been loaned a map of the town from the 1870s. It is clear from the number of buildings (both residential and business) that the town was large enough to have a population in excess of about 200, so that the high death rate of the 1870s, while unusual, would not necessarily imply an influx of people from outside the town. So our investigators decide to treat this as a wholly local phenomenon.
As the two investigators are discussing the tombstone data and the map, a person walks over to talk to them (they have let it be known that they would like people who have any insight into the history of the town to stop by and tell them about it). They learn that the 1870s were famous for a series of very severe winters.
Ah ha! They immediately hypothesize that the severe winters were the cause of the very high death rates. Note that they have not actually proved anything they simply now have an hypothesis to work with.
While they are busily taking notes about their conversation with the first person, a second walks up and informs them that the 1870s were well known for numerous years of crop failure, and also for a number of years when all the local farmers livestock was decimated due to disease. Hmm, a second hypothesis is born starvation and malnutrition.
Our investigators start to take more notes, but while they are the two towns people begin to argue. The first claims that the crop failures were not that severe (he claims his great-great grandfather left a diary which proves his point); while the second claims that the cold winter stories were overblown (he also has family history evidence).
While the argument rages, a third person comes over and starts to tell the investigators about the great fire of 1876, which burned the entire town to the ground. This, he claims is when most of the people died during the 1870s.
This third hypothesis (a catastrophe) gets the first two towns people to abandon their argument, and turn their attention to telling the third person why hes wrong, and the argument flares again.
Our two investigators are now left with three valid hypotheses, little data to test them with, and three towns people arguing at the top of their vocal range. They try to sneak away to the town library and examine the (meager) demographic data to test the three hypotheses.
If you substituted "paleontologists" for "investigators, and instead of "towns people" used the terms geophysicist, geochemist, and stratigrapher, you might have an idea of what the question of extinction in the fossil record is like. The paleontologist sees that a major extinction event has occurred in the past, but must rely on other disciplines to "prove" the cause. In many cases each of the other disciplines does provide valid evidence indicating that certain events occurred, but the simple simultaneous (or possibly simultaneous) occurrence of two event does not prove causality. For example, if you see a traffic accident occur exactly as the local church bell strikes the hour, does that mean that the striking of the bell caused the accident? It could have if the noise of the bell distracted one of the drivers; but could have is not the same as did!! Unless a clear cause/effect relationship can be shown to exist, we are simply making an interpretation which may eventually be falsified by the appearance of new data. Such is life when you study ancient extinctions.
The Neontologist theyre dropping like flys, but nobody wants to believe us!
The problem faced by neontologists is just the opposite of that faced by the paleontologist. The neontologist sees change taking place which is detrimental to organisms, often sees the shrinkage (if not total loss) of species populations, but must build a case to support the hypothesis that we are in the midst of a major extinction event. The neontologist often faces problems of politics, human custom or heritage, and simple human needs (food, livelihood, living space) which are rarely faced by the paleontologist.
If we were to try to create an analogy in this case, we could begin a physician in a large city. The physician has seen demographic data (and even a few of the sick people individually) plus reports indicating that all the forcing mechanisms for widespread illness (overcrowding, poor sanitation, malnutrition, etc.) are present in the city and increasing in intensity. Furthermore, death rates have risen over the last few years, but the data is insufficient to statistically prove the presence of a trend.
The physician can examine individuals (but not the entire population of a city), in many cases determine the exact way that a forcing mechanism produces illness in an individual, even visit the worst parts of the city. All his data then leads to a prediction (an interpretation of trends).
When our physician presents his findings to the mayor, along with a report suggesting a course of action, he is met with less than whole-hearted support. The mayor agrees that the report is disturbing, but does the physician know how much his planned course of remediation would cost? The mayor would need to raise taxes, close down some industries which appear to be polluting the citys water and air, etc. How can he even consider this course of action based on the rather shaky data presented by the physician?
Sadder but wiser, the physician leaves the mayors office and begins to develop a plan of action which will allow him to save those that can be saved.
Not a pretty picture.
In summary, the paleontologist can examine the graveyard of species, and warn us that very nasty things have happened to the bio-sphere in the past, and could well happen again. With the aid of other scientists, they can even suggest some of the forcing mechanisms. Neontologists, on the other hand, see a very poor time for the bio-sphere on the horizon, attempt to prove that their predictions are valid, and also attempt to chart out the best plan to save what can be saved.