But New Guinea does not divulge its secrets readily. “There’s a very limited road system, and most of our travels are either by foot or by small airplane,” says Austin, who often spends weeks camped on the banks of the Sepik River in the north-central rain forest where he collects lizards, snakes, and frogs. Back in his lab at Louisiana State, he analyzes their genetic material to better understand how New Guinea’s many unique species diverged from their relatives and took on their distinctive forms.
Every new species that Austin discovers is another piece of the puzzle. And because of the looming threats created by global climate change, what he is uncovering in these remote rain forests could have far-reaching consequences. “We are in the midst of one of the most remarkable patterns of extinction that has ever happened,” he says. The current temperature spikes are destroying delicate ecosystems and threatening the survival of millions of species of plants and animals around the globe. “We need to understand the balance between extinction and speciation [the creation of new species] if we have any hope of salvaging this planet.”
Neil Shubin holds part of a Tikaalik roseae fossil.
Image courtesy of Dan Dry, for the University of Chicago
The Canadian Arctic
In 2004 on a remote island in the Arctic wilderness, American scientists uncovered the remains of a fossil fish, Tiktaalik roseae, that first crawled on land about 375 million years ago. The find has deepened our understanding of this crucial evolutionary milestone and has illuminated the complex bodily changes that occurred when our distant ancestors moved out of the water. Tiktaalik is a strange creature, a combination of the limbs, skull, neck, and ribs of four-limbed animals and the more primitive jaw, fins, and scales of fish. It seems to be an intermediate step between fish and land-living animals, a key link in the evolutionary chain that led to amphibians, reptiles, and dinosaurs.
Researchers had conducted five annual fossil-hunting expeditions to Canada’s Ellesmere Island, 830 miles south of the North Pole, before they finally hit pay dirt five years ago. The conditions were harsh. Even in July, when the sun never sets, there were freezing temperatures, high winds, and nearly constant rain. One afternoon a member of the team spotted what looked like the snout of a flatheaded fish sticking out of a cliff.
“We figured we’d find the rest of the skeleton inside the mountain, which is exactly what happened,” says Neil H. Shubin, a team coleader and an evolutionary biologist at the University of Chicago. “Even though we had suffered through the dreariest weather imaginable, we were elated beyond belief.”
The newly discovered fossil fish was a predator that could reach nine feet in length. It lived in shallow freshwater but was able, researchers believe, to pull itself out of the water and move around on land. (The name Tiktaalik means “large freshwater fish” in Inuktitut.) In the late Devonian period, nearly 400 million years ago, the area where the fossils were found was near the equator and had the temperate climate of the Amazonian rain forest. As the earth’s continental plates shifted, the land drifted north to the Canadian Arctic.
An analysis of Tiktaalik’s anatomy, completed this past October, indicates that the evolution of fins into sturdy limbs was accompanied by other anatomical innovations, including the rudiments of an articulated neck. “What allowed this lineage of animals to start to exploit the land was not just a matter of changing the fins to limbs but also the ability to move their head so they could navigate in shallow water,” says Ted Daeschler, a team coleader and a paleontologist at the Academy of Natural Sciences in Philadelphia. “The fossil record has shed light on these major evolutionary shifts.”
Bacterial filaments entombed in limestone
at the Cuatro Cienegas basin in Mexico
Image courtesy of
Dr. Jack Farmer, Arizona State University
The Chihuahuan Desert
Cuatro Cienegas, nestled in a valley surrounded by towering mountains, is an oasis in northern Mexico’s Chihuahuan desert, with more than 400 ponds and outlet streams fed by underground springs. Scattered over 200 acres, these pools of sparkling blue water are home to 70 species of plants and animals that are found nowhere else on earth. The area has become a mecca for scientists, in part due to the presence of stromatolites—reeflike structures created by blue-green algae that were abundant before the rise of multicellular animals. The unique ecosystems of Cuatro Cienegas may yield insights into what sparked the Cambrian transition, a pivotal time about 540 million years ago when simple, single-celled life developed into a wide variety of multicellular forms.
“There was a sudden and explosive diversification of animal life from some trigger that we haven’t as yet identified,” says Jack Farmer, a paleontologist at Arizona State University in Tempe. “Cuatro Cienegas may provide clues because the mechanisms that control the region’s biodiversity may have operated during the Cambrian period.”
Scientists have found that about half of the organisms at Cuatro Cienegas are most closely related to marine life, even though the oases here have not been in contact with the ocean for tens of millions of years. “How do you get marine organisms so far from the ocean?” wonders James Elser, a biologist at Arizona State who makes regular trips to the site. “One theory is that they were deposited as the geological system formed and were trapped inside limestone until they were liberated eons later to form their own ecosystems. There’s a vestigial community—an experimental time machine—and studying them in the present might tell us something about the past,” Elser adds.
The Intensive Care Unit
In a perfect world, hospitals would strictly be places where the sick go to get well. Unfortunately, the hothouse environment of the hospital provides a window into an insidious side of evolution. All too often an epic battle for the survival of the fittest is taking place on almost every ward, transforming what should be sterile surfaces into incubators for antibiotic-resistant bacteria.
Because infectious microbes reproduce quickly and have enormous populations, changes in their genetic makeup over several generations can show up in just a few days. Moreover, they are up against overwhelming natural selection pressures: powerful antibiotics that kill off all but the hardiest microbial mutants. This ratchets up the normally leisurely pace of evolution by many orders of magnitude. “It’s Darwinism at its finest,” says Carl Bergstrom, an evolutionary biologist at the University of Washington in Seattle who studies drug-resistant bacteria.
Hospital-acquired infections kill 90,000 people a year—more than HIV, breast cancer, and influenza combined. The magnitude of the problem has scientists like Bergstrom in a race against time as they attempt to harness what they know about evolutionary theory to slow the rate at which bacteria become resistant. Bergstrom’s tools are computers and mathematics, and the testing grounds for his ideas are the hospital intensive care units that provide him data.
“We keep inventing new antibiotics, but bacteria evolve resistance almost immediately, so we’re constantly playing catch-up,” he says. “How can we make the best use of the antibiotics we’ve got now? We’re using mathematical models to generate hypotheses about how we can shape and alter prescription practice to minimize or delay the evolution of resistance.”
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