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It is surprisingly cold in Florida at two and seven in the AM. I may have to start bringing a sweat-shirt with me for the mornings and late evenings, or go back to layering. I suspect that the temperature is already on its way up to the high 80's for this afternoon.
Not a complaint - just an observation. I worked on my statistics homework and did the taxonomy reading by the poolside yesterday afternoon...
Today was another good day. I spent most of it on a desolate and barren hillside in the middle of a gravel quarry, hunched over a mountain of clay - and armed with only a screwdriver to sift through it - but today was still a good day. I may have burned out my brain in the hot hot sun, but I was searching for buried treasure, and I found it.
We were digging in a two million year-old sinkhole that once lay at the bottom of a Florida lake. The lake acted as a funnel to the sinkhole's drain, and the depth of that hole promoted an anoxic environment, deterring further scavenging and predation. This created conditions favorable to the preservation of a large number of whole and partially articulated skeletons. You might be surprised by the diversity of life represented in this unusual watery grave - any number of things can fall in a lake and drown over a few thousand years.
I spent the first half of the day slowly filling and then emptying bucket after bucket with the dust of ages, all while watching my peers - who sat less than three feet away from me! - unveil a series of perfect turtles, tapir legs, a few ribs, and the miscellaneous bits of a giant ground sloth. What I was doing was important - I was 'shifting dirt', and the vast majority of paleontology and archeology involves a lot of this particular task. If every poke of the shovel constitutes an experiment with the accompanying hypothesis, "is there anything down there?", then the majority of experiments in these sciences result in failure. Still, every bucket of dirt I shifted was another bucket that somebody else didn't have to - and these sciences are also about comparing the means of many many samples.
While hits may initially appear randomly distributed, they tend to cluster.
Eventually, just as I was beginning to think about heading home and working on my statistics homework, I struck paydirt.
After four or five hours of fruitless searching, you immediately recognize when your awl touches fossilized bone instead of just another lump of limestone. Every sensation is different; the sound, the shock of connection transferred up your arm, and the resistance of the bone within the clay. Even the color, once revealed, is different: at this locality, the bones have a reddish cast that is totally unlike that of the thick grey of the clay or stony white of the limestone that surrounds it. A rising "hmmm..." seems to be the "eureka" of choice among the diggers in the dirt, and each canto is followed immediately by its response from your neighbors: "any idea what you found?"
The thrill of discovery surges through you, and the heat of the afternoon and the ache of tired muscles and bent backs falls away in an instant. Your efforts are immediately redoubled, and you begin to scrape precise spalls of clay away from your source. This is as much art as science, and the careful hand of the sculptor is vital. You shave away the matrix, freeing the bone locked beneath. You do not want to disturb or damage a delicate fossil that may well turn out to be unique. Once released, the piece is bagged and tagged with a field number identifying the locality, depth, and date it was uncovered. The name of the collector is attached, and in some small way I have achieved immortality: wherever these pieces travel from here, they will also carry my name into the future of science.
If you have found one piece, you may have found another, and you never know just how much of the iceberg lies beneath the surface. You can circle around your find site, hoping to trace the line away from your single point that will lead in the direction of a miraculously complete skeleton and the incredible satisfaction of having found something that no one has seen in a very long time.
I did not unearth anything terribly spectacular: the toes of a long-dead giant armadillo, and a few scutes from its tail. The carpals of a tapir's toe.
It was still more than enough to make my whole afternoon worthwhile.
A good many have asked my thoughts on the progress of graduate school thus far, and while I remain conflicted on some of the details and my nuanced response could go on for pages, there really is a simple answer. If any one thing underlines my experience thus far, it is this:
science is fun again.
This juvenile specimen was discovered observing a small school of fish in a drainage ditch along the edge of Lake Alice here in Gainesville. It was just over a foot in length, and approximately a quarter-inch in thickness. Some have alleged this beast a rat snake, or corn snake - so known because of their propensity to consume rats in barns, and because their coloration provides for excellent camouflage in the original red-colored strains of corn grown in North America. That said, there also exists a possibility that this is the altogether more fierce Florida banded water snake. My favorite herpetologists wished that I had handled the snake in order to obtain better pictures of his ventral scales, dorsal banding patterns, and his skull morphology - so that they might reach a more authoritative conclusion.
I was far too smart to try handling an unknown (and possibly venomous!) organism without good thick gloves on - and besides, I really am more of a "sit back and observe what happens" than a "poke it with a stick and see what happens" kind of scientist. Call me lazy, but I'd prefer for the organism to inadvertently perform the passive experiments itself than for me to force a situation upon the serpent where it must make an active decision about its lifestyle.
I left the snake a good two or three feet for him to feel comfortable in. Even so, he didn't do much more than move his head four or five inches the whole time I was there - he was nervous. Once I got back up out of the ditch and moved back to seven or eight feet, he slithered slowly forward and around the bend of one of those rocks into the undergrowth with increasing acceleration. He wanted to be gone once he thought I was out of grabbing range...
Besides: after being chased by water moccasins in a former life, I felt justified in leaving a few feet for me to feel comfortable and hope that I would have a good running start to get away from any hornked-off snake...
Sometimes love is all you have against the dark.
In spite of belonging to one of the most diverse orders of mammals, with over a thousand separate species classified, bats remain something of a mystery - often unobserved by the casual naturalist. Perhaps I tend towards a Chinese interpretation of things because of my childhood travels, but I must admit that I have long been rather fond of the nocturnal wonders. While I can not be certain, I suspect that I saw my first real bat long ago at the Denver Zoo, but my earliest memorable encounters with the creatures in their natural environment were never through their direct presence, but always of the carnage they left in their wake.
While living in Singapore, we had an enormous mango tree growing in the front yard of our home on the hill at 8A Rochalie Drive, but we never did get the chance to taste the mangoes that grew from that tree. As soon as they would begin to ripen, an unseen horde of flying foxes would descend out of the Malaysian sunset and devour the fruit, scattering their thick guano - now rich in partially digested mango - all over the driveway. This relationship presented a classic example of inadvertent predatory mutualism. The mango tree expends energy producing fruiting bodies to support its offspring, but by day the rich ethylene put off by the ripening fruit attracts birds and primates - and by night it draws bats who also consume the fruit. Mango seeds which can not survive passage through the intestinal column of a frugivore are gradually winnowed from the population - or at the very least, face a competitive disadvantage when compared to siblings or neighbors' seeds that can survive the process. Trees whose seeds do survive the transition may be carried some distance from their parent before being dispersed, thereby helping to expand the mango's range, and hopefully prevent competition between proximate family members. This process has been so successful that there are some mangoes for whom selection has encouraged germination only upon contact with fruit bat stomach acids after ingestion. Evolutionary relationships aside, as the season wore on, this rotting fruit would begin to ferment in the humid and warm air, and the atmosphere could become positively narcotic. Our low-slung cairn-terrier would avoid the shadow of that tree, but our evil little cat would at times bask in the alcoholic vapors, after which he would become positively silly.
My next memory of bat-contact would also be indirect, and it would take me some time to realize that I was again observing their handiwork. For some time, I had seen banana leaves and palm fronds with small cuts chewed into their undersides, perpendicular to the lobes of the leaves. These tiny cuts weakened the cross-sectional strength of the lobate processes on a leaf, and they folded along these lines, forming a small tent-like structure. One morning while waiting for the fourth-grade school bus at the top of the hill on Rochalie Drive, I happened to look up and discover the culprits responsible for this unusual gardening: a knot of tiny white-furred bats roosting in the folds of a banana leaf some thirty feet above my head.
Years later, I would watch in wonder as thousands of fruit bats left their chattering camp to pillage some hapless fruit plantation somewhere in Northern Australia. Their coterie began with one or two flyers leading the way, and eventually grew into an endless stream nearly a dozen individuals thick. The whole flock took nearly half an hour to pass, a river of airborne terriers, steadily and silently wending their way into the gradually darkening sky. It is easy to see why many farmers consider them an agricultural catastrophe, as flocks of this size are allegedly capable of denuding an entire orchard in a night.
Of course, only a third of bat species are frugivorous. The major division in bats is between suborder megachiroptera and suborder microchiroptera, and while the larger-bodied megabats tend to rely on a phytovorous diet high in sugars, the microbats tend towards carnivory. In particular, the microbats lean towards insectivory, taking up the challenge and the ecological niche of "small volant predator" when the swallows go home to roost for the night. These are the bats whose famous echolocation drives their dazzling acrobatics as they dive and flitter before bright stadium lights for moths and the precious fat they carry. I've been watching small bats of an indeterminate species flit before the arc-sodium light over my apartment complex's parking lot for the last five years, and I recently played host to a small colony living inside the bedroom wall of my apartment for a few weeks late in December of 2005. They woke up and began their flight at seven to eight in the evening, and returned between one and two in the morning. While their chittering was often comforting to one who has lived alone for far too long, my apartment complex elected to have them removed. While the bats themselves are mostly inoffensive, their droppings could provide a nutrient rich home for many noxious fungi and bacteria that could grow and spread throughout the walls of the complex.
Just as the habits of living bats remain somewhat mysterious, their evolutionary origins are also considered controversial. The earliest known bat fossils are found from 50 to 52 MYA in the Eocene, but their crania are already in possession of the traits key to echolocation in extant microbats, and their fossils are also already broadly distributed across the globe. Creationists seize upon this "full-formed and sudden appearance" within the fossil record without a solid lineage of transitional fossils as evidence refuting evolution. It is unfortunate that bats, like birds, are small-bodied animals with fine bones that rarely survive the process of fossilization. Worse still, the majority of extant species of bat live in tropical forests whose environments are even less conducive to the creation and preservation of fossils, and it is presumed that their extinct ancestors may have lived in similar environments. In spite of these difficulties, the dentine in teeth preserves remarkably well, and incisors showing intermediate properties of Order Insectivora and the insectivorous microbats have been discovered in Cretaceous and Paleocene rocks. Of course, there is no telling what the rest of the organism might look like...
Modern "creation science" also likes to speak of "irreducible complexity", and some would claim that the evolution of flight in bats is just such an impossible trait, because there could be no successful transitional organism between full flight wings and webbed fingers. These individuals lack imagination, and I believe that I need point no farther than the relative diversity and abundance of the so-called 'flying frogs' - also of southeast asia. Remember that there are no 'partial traits' on any living organism: only fully functional traits that can be exploited with varying degrees of success! More importantly, the initial function of a trait may create spandrels ready for exaption to another function. Organisms may have webbed feet because their ancestors used them to swim, or because they act as a fly-swatting net to capture prey, or to glide from tree to tree - but their descendants may accidentally adapt them to a new alternately useful purpose.
Having personally witnessed some of these oddities glide from tree to tree, or using their webbed forelimbs as a fly-swatter to capture or stun prey while terrestrially bound, I can assure you: while the transition between partial gliding flight via webbed feet, elongated ribs, or full-body patagia may be a difficult path, it unquestionably provides a prior selective advantage to the individual in possession of these 'partial traits'. Conveniently enough, a recent paper demonstrates a mechanism by which bats' long fingers might have evolved. It appears that mutations leading to an up-regulation of bone morphogenic protein-2 (BMP2) (or the down-regulation of BMP2 antagonists such as Noggin) in the distal phalanges would result in the elongation of bat forelimb digits, providing a mechanism by which early proto-bats might literally have flown over some adaptive constraints on the path to flight.
All of this still fails to explore the actual controversy in real science: the confusing relationship between the mega- and microbats - and fails to answer where their branch or branches anchors to the tree of life. Much as tarsiers have proven difficult to classify, so have the suborders of bats - and for similar reasons. Without strong fossil evidence pointing its stony fingers at a particular time and event, it is near impossible to tell whether the megabats or the microbats evolved first, and if so - is one line derived from the other? At first glance, the relationship seems obvious - the megabats and microbats share many presumed ancestral character traits in common, but the microbats possess the derived traits contributing to echolocation. A closer analysis of skull morphology reveals some interesting differences. Morphologically, microbats share many traits in common with Order Insectivora - and surprisingly enough, the megabats share many significant traits with Order Primates. This has led some researchers to declare the megabats flying primates, relatives of the Dermoptera. Of course, filing colugoes under a particular branch has proven equally difficult. Even molecular studies remain somewhat inconclusive.
Only time and more research in fields of both paleontology and molecular science will let us know for certain. Until then, I will just have to watch and enjoy the bats at the University of Florida's bat house.
