Jack Dumbacher's interests include the ecology and evolution of birds and molecular ecology. While he's traveled the world to study birds, his most recent expedition focused on the round-eared elephant shrews of the Namibian desert.
One of the harshest places on earth is the desert of Namibia. Stretching a thousand miles along the coast of the Atlantic in Southern Africa, it contains some of the highest sand dunes in the world. Almost completely barren and largely uninhabited by man, the desert is one of the oldest in the world. Animal populations have evolved in the pristine isolation of the Namibian desert for approximately 55 million years.
That's precisely why curator Jack Dumbacher wanted to go there.
As forbidding as it is, Namibia is an ideal place for a field research expedition since it is relatively undisturbed by man.
Dumbacher has spent much of his time in this inhospitable environment looking for the round-eared elephant shrew. This tiny creature, about the size of a gerbil, feeds entirely on ants and was incorrectly thought to be the relative of shrews, moles, and hedgehogs.
While humans have hunted large mammals and encroached upon their habitat, they've overlooked the tiny elephant shrew. This creature is particularly interesting to Dumbacher because understanding the genetics of small animals like the elephant shrew can can help us learn more about evolution in Africa.
Dumbacher went to Namibia to see if the different colored elephant shrews that existed in different parts of the country were the same species. On the coast, the animal tends to have reddish fur. In the high desert escarpment, they are darker in color. Dumbacher wondered if the color types interbred—if they exchanged genes—or if they were different species.
On his expedition, Dumbacher caught a number of elephant shrews and collected DNA samples. Back in the lab, Dumbacher sequenced the DNA to look for gene flow between populations, working to broaden his understanding of the species boundaries.
Once thought to be the relative of moles, the elephant shrew is recognized as a solitary offshoot on an ancient African branch of the evolutionary tree. Their closest relatives include elephants, sea cows, and aardvarks. In an unexpected twist, the elephant shrew of Namibia is more elephant than shrew.
Evolution and Math
Dumbacher began his scientific career with a background in math, a passion that still informs his study of evolutionary biology. In college one of his favorite classes used mathematical models to explain altruistic behavior and cooperation. The ability to boil down the complexities of life using a simple mathematical construct appealed to Dumbacher. He says that´s what led him to seek out the math geniuses and population geneticists at the University of Chicago.
Mathematical models can reconstruct the evolution of organisms. The basic organizing principle of evolutionary biology, the so-called tree of life that explains the genetic relationships of living things, is essentially a mathematical construct.
Math can be used to understand evolution, diversity, and the spread of species. The same patterns Darwin saw can be explained and predicted in a mathematical equation. Scientists use gene sequencing to track the evolution of a single gene through time. The mathematics that underlie these genetic sequences enable them to see how traits are inherited from one generation to the next, and how a gene moves through a population or even an entire species.
Mathematics can boil down the complexity of evolutionary biology into simple constructs. Has the gene been selected or not? A mathematical model can examine slight variations in selection over hundreds of generations and can make accurate predictions about gene frequency. Statistics and regression analysis provide an elegant way to measure and predict genetic selection in great detail.
Mathematics makes for a rigorous way to refine models and make better predictions, which ultimately leads to better understanding. Combined with molecular genetics, chemistry, and biogeography, mathematics is just one of the tools and techniques scientists use to understand evolution, biodiversity, and the distribution of animal populations on the planet.
As Dumbacher says, “The more we understand how animals evolve, the more we understand how we are evolving. The forces that are pushing animals to evolve push on us, too. The more we know about nature, the more we know about ourselves. The more we know about ourselves, the better we can make decisions about our future.”
A Poisonous Bird
Some of the best discoveries in science are completely serendipitous. Jack Dumbacher discovered, quite by accident, that common New Guinea birds use potent poisons for protection. While trekking in the bush with a tribesman in Papua New Guinea, Dumbacher released a jay-sized songbird called a “pitohui” from a mist net. In doing so, he cut his hand and developed a burning sensation. Dumbacher popped the cut in his mouth. Soon his lips and tongue began to tingle and burn. “The effect lasted for hours,” he says.
Later, in the interest of science, Dumbacher gamely popped a pitohui feather in his mouth. Immediately, he felt the same burning sensation, just as if he had placed a nine-volt battery on his tongue.
He asked his guides about the pitohui, and was told that they were rubbish birds, good for nothing. “You can't even eat them,” his local helpers said.
Dumbacher realized he was onto something. He thought this might be the only case of a poisonous bird ever found, and began a study of the chemical defenses of the pitohui.
Dumbacher had known of chemist John Daly's discovery of the Colombian poison dart frog in the 1960s. Many schoolchildren learn that monarch butterflies are poisonous, using their brightly colored orange-and-black wings as a signal to birds to stay away. Dumbacher thought the pitohui might use a similar defense mechanism. If that were the case, it would be the first—and only— known case of a poisonous bird ever discovered.
At a University of Chicago speech, Dumbacher brought along his bag of feathers, and passed them out among the audience. Butch Brodie, a behavioral neuroscientist, was in the audience. He tasted a feather, immediately recognized it as a poison, and passed a sample along to one of the nation's premier chemists, John Daly, at the National Institute of Health. Daly was the same man who isolated the poison in the Colombian poison dart frog in The '60s.
Using direct probe mass spectrography, Daly mashed the feathers into a potion, dried the substance, put a sample on the tip of a probe and bombarded the mass until it broke down into its chemical constituents. Daly discovered batrachotoxins identical to the poisons found in some species of frogs. According to Dumbacher, “No one else in the world had the machinery and the know-how to recognize this as a batrachotoxin.”
Extremely rare in nature, the toxin attacks the nerves and muscle membranes. The toxin disrupts the firing mechanism of the nerve, which results in a tingling sensation and numbness. In higher doses this can result in paralysis, cardiac arrest, and death. Gram for gram, batrachotoxin is the most potent neurotoxin in the world. And it was located on the feathers of a pitohui. The pitohui—half a world away from Colombia—shared the same potent neurotoxin as poison dart frogs.
The response to the discovery of a poisonous bird made a huge splash. Dumbacher's claim—that this was the first known poisonous bird—earned enormous attention in the field of ornithology. The bird became famous, and interest in the field rose. Today, Dumbacher has identified five more species of poisonous birds and, in another first, may have discovered the source of the bird's poison. Turns out the pitohui eats a beetle chock-full of the same poison. Now Dumbacher can add to his list the first insect species ever identified as a carrier of batrachotoxin.
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