Science is many things to many people, and some of these things are the results of distortions in the popular culture, often by way of political or commercial propaganda.

Hitler and Stalin both called their politics scientific. The former gave the world the horrible experiments of Dr. Mengele, and the latter the state-sanctioned frauds of Dr. Lysenko. One of the older and less subtle forms of deceptive advertising is to dress someone up in a white coat and have that person declare that Brand Y is "37 percent better" (than what? according to what measure?). The mad scientist is a standard fixture at Central Casting. (This reporter prefers the nihilistic kind, the ones who want to destroy the world, over the boring venal creeps who seek mere planetary domination --- though Pinky and the Brain are an exception.)

When it comes to evolution, certain breeds of religious zealots have come up with "creation science," a line of inquiry that starts with the premise that ancient interpretations of even more ancient texts are literally true in every respect, and then seeks ways to explain away creosote rings, fossils, isotope dating techniques and the geological records of sedimentation and continental drift in order to uphold the original idea.

But of course, all of the above-cited ways of thought and argument are unscientific. Science is a systematic method of searching for the truth, one that starts with observation of facts, continues with attempts to explain those facts, and proceeds to experimentation and new observations designed to test the attempted explanations. If the whole point is to find evidence that blacks and Jews are genetically inferior to Germanic and Nordic types; or to demonstrate that Father Mendel was an obscurantist and racist whose observations of peas are irrelevant to agricultural science; or to prove that Company A deserves to overwhelm Company B in the marketplace; or to develop a radiocarbon decay curve that shows that the dinosaurs lived 6,000 years ago, then the process is too arrogant and presumptuous to be called scientific. The true scientific attitude is much more modest and open-minded.

These days the mountains of evidence gathered by scientific processes uphold the basic theory that Charles Darwin explored, that processes of natural selection and adaptation lead to the emergence of new species. That's the way that the chips fall, notwithstanding the protests of right wing members of the committee that chooses textbooks for Texas public schools.

However, true scientists don't worship idols, and acknowledge that Darwin, who died 120 years ago, did not discover the final and eternal truth about evolution in all of its details. Darwin's theories and hypotheses raised more questions than the man was ever able to answer, and subsequent generations of scientists have on the average uncovered several mysteries for each revelation.

The search for evolution's keys continues in Panama, especially at the Smithsonian Tropical Research Institute (STRI). The subject frequently comes up at the weekly scientific lectures that take place every Tuesday at noon at the Tupper Center Auditorium in Ancon and every Thursday night at the conference room on Barro Colorado Island. On August 20 and 22, two scientists with different specialties attacked the problem from two different angles for audiences primarily composed of other researchers.

At the Tuesday forum, STRI biologist Egbert Leigh reviewed theories and investigations about why there are so many different kinds of tropical trees.

The first part of Leigh's presentation was a mathematical argument about the notion of random environmental variation. The biologist noted that people can plot and have plotted the average rate of change in the fossil records of the relative proportions of certain kinds of trees in given forests. With rare species, as time goes by the frequency with which they are found is based upon its reproductive success in comparison to other species. "Species will drift away from equal frequency," Leigh noted. "You will expect one species to have knocked the other one off."

But when there are overlapping generations of trees and ecological niches with limited ranges, then the theory of random environmental variation becomes much less predictive. "The main fault with this theory is that it's very hard to embed it in a finite system," Leigh concluded.

That, however, does not kill random environmental variation for Leigh. He finds that by using averages instead of raw numbers in the equations, distribution models become "more realistic." While allowing that there's room for more inquiry, so far he finds the theory "a low-grade mathematical argument" that "doesn't quite get rabbits out of hats." The main lesson he draws from this attempt to explain the proliferation of tropical tree species is that "you can't get process from pattern."

Leigh went on to review research in diversity gradients, inquiries directed at understanding the balance between speciation --- the rise of new species --- and extinction. The problem with this field at the moment, he said, is that we don't know very much about the speciation of tropical trees.

He said he found an interesting lead, however, in a recent study on inter-species pollenation of types of ginger. It turns out that two different species found far away from one another can be cross-pollenated, but two plants of the same species will not become fertilized by each others' pollen.

When one makes the hybrids and then tries to grow them in the natural conditions from which either of the parent plants hail, it has been found that the hybrids don't thrive as their parents did. Most likely this means that the parents were specialized at living in specific niche, and that the advantages of this specialization are lost in the hybrid offspring.

The ginger study suggests new lines of inquiry about trees to Leigh. For example, philogeographers could look at closely related tropical tree species to find out whether they tend to have overlapping, adjacent or widely separated ranges. Researchers might try to discover why tree diversity is much lower on tropical islands than in the continental tropics. The fossil record might be expanded and more closely examined to see if it can tell us why tree diversity was greater in the Miocene epoch (25 to 10 million years ago) than it is now.

"It would be very interesting to know how difficult or rare speciation is," Leigh concluded.

At the Thursday night talk on Barro Colorado Island, paleontologist Helena Fortunato took on the subject of speciation by way of her studies and those of colleagues about little snails of the strombina group, past and present.

It turns out that various species of these marine mollusks are found in relatively shallow waters off both sides of Panama, and in fossils dating back millions of years. Because the different strombina species in and around the isthmus have been well collected by several generations of scientists beginning especially during the canal construction era, Fortunato said, "this region happens to be ideal" for her inquiries into the biogeography of speciation and the extinction and origination of related snail types.

Continental plates drift to and fro over geological time, and there was a time when the Isthmus of Panama was not in place and did not separate the waters of the Eastern Pacific from those of the Caribbean Sea. In fact there is evidence suggesting that by way of rising and falling sea levels the interoceanic barrier that's Panama has been breached at least once between the time that it formed several million years ago and the completion of the Panama Canal in 1914.

The record shows that some strombina species disappeared from the Caribbean but persisted in the Pacific, and that long ago there was a greater variety of the snails in the Caribbean, but now there are only a few Caribbean species while Pacific strombina have proliferated into many more forms.

So why is that? Fortunato doesn't have the certain answer, but she's looking into it.

"When we think about speciation, we tend to think about barriers," Fortunato noted. But what caused the speciation that's known to have taken place in environments where there is rather continuous shallow water?

Fortunato's presentation was in large part a series of slides that depicted different lines of inquiry aimed at answering this question. Some of the snails she studies prefer to live on rocky substrates, while others like sand and others stay in the mud. Certain strombina go through a larval phase, while others directly reproduce tiny snails. Forms that produce larvae are much more common in the Pacific than in the Caribbean. When the fossil record is reviewed, it shows a burst of speciation about five million years ago. About 22 percent of the species she looked at are "transisthmian," that is, exist on one side of the isthmus and are descended from species on the other.

The definitive proof has yet to be found, but Fortunato suspects that climatic changes may have isolated certain marine mollusk populations for relatively brief times by creating slight changes in temperature, salinity or sea bottom conditions, and that this may have been enough to trigger speciations.

During the question-and-answer period between the end of her presentation and much of the audience's departure on the boat back to Gamboa, Fortunato's answer to a couple of questions was "I don't know." While one might expect that a religious zealot looking for proof that scientists trying to discover the mechanisms behind the origins of the species are a bunch of blasphemous fools would take heart from such admissions, there was no trace of embarrassment in the paleontologist's expression or the audience's reaction. Such candor and modesty are hallmarks of the attitude we call science.

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