Are we alone in the Universe? Astrobiology

Two of my astrobiology colleagues: Andrew Steele (l) and Steve Shirey (r), Carnegie 2012

“The probability for the chance of formation of the smallest, simplest form of living organism known is 1 to 10,340,000,000.... The size of this figure is truly staggering, since there are only supposed to be approximately 10⁸⁰ electrons in the whole universe!” Harold Morowitz, in Energy Flow in Biology (1968).

         In 1996, NASA announced that it had found evidence of life contained in the Martian meteorite Alan Hills 84001 (McKay et al., 1996). They held press conferences and presented evidence for what they termed bacterial cell structures in the meteorites, along with some amino acid profiles. News spread like wildfire among Mars aficionados and skeptics alike. The search for life on Mars stimulated several lander and orbital missions to Mars. At the same time, NASA under the advice of Wesley T. Huntress, Associate Administrator for Space Science, had the idea to form the NASA Astrobiology Institute (NAI), a virtual institute in which scientists in disciplines as far-ranging as astronomy and astrophysics would regularly engage with molecular biologists and geochemists. Objectives central to this effort were to understand how life arose on planet Earth, to determine when it arose, and to devise a set of criteria everyone could agree on that constituted evidence of life.

         This task has been more difficult than it sounds. To this day, NASA and NAI scientists still are discussing how they will determine which chemical or physical line(s) of evidence constitute proof that there is life on another planetary body. I was part of two original NAI teams that took very different approaches to search for life. The Jet Propulsion Lab (JPL) team focused on biosignatures. Biosignatures are fingerprints of life such as isotope fractionation patterns or elemental ratios. Ken Nealson, who specifically moved from University of Wisconsin to JPL, led the effort. Our work was carried out in both modern extreme environments as well as in ancient rocks. Being on the JPL campus, this NAI team used several new techniques that were being specifically designed for space flight. The goal of this group was to develop biosignatures in tandem with new analytical methods in the lab to help us to understand the significance of biosignatures observed in the field. 

(L-R) Wes Huntress, Doug Rumble, Marilyn, Ken Nealson, 2002

         On a geological time scale of hundreds, thousands, or millions of years, biologically-resistant material gradually obtains an isotopic and chemical composition that has little resemblance to original biochemical compounds. If we were to find evidence of life in martian rocks billions of years old, we needed to broaden our thinking. Rather than searching for pristine molecules similar to ones in living organisms, we needed to know what these molecules would look like—their biosignature--after they had been substantially degraded. Working with postdoc Sue Ziegler, we fed a simple mixed culture of microorganisms a single protein, Rubisco, the protein I studied for my PhD work. The bacteria ate the Rubisco protein completely in about 36 hours, turning the Rubisco protein into their own bacterial proteins.

         We compared the chemical isotope biosignature of the amino acids in the Rubisco with the isotope biosignature of the amino acids in the microbes. The biosignatures were completely different. After the bacteria had eaten the Rubisco, some slightly larger heterotrophic organisms ate the bacteria. Bacterial proteins were decomposed and recycled into these larger beasts. In a very short time, hours to days, the original Rubisco protein isotope biosignature had been altered twice. In the real world, almost any biomass made by plants and animals is quickly metabolized by microbes and almost never enters the fossil record. It is a reasonable assumption that if there were living organisms on another planet, a similar hierarchy of organisms would probably have evolved.

         The approach by the Carnegie team, which I also worked with, was completely different. Geophysical Laboratory staff member Bob Hazen and Harold Morowitz (George Mason University) had the idea that we might be able to study some of the most basic reactions fundamental to all organisms.  Bob Hazen is an accomplished writer of popular science books, textbooks, and scientific articles in his discipline. Over the years, I watched him transform from a high-pressure mineralogist to an astrobiologist to a big picture thinker on the nature of carbon in the deep earth. He was never a “lab guy” like the rest of us at the Geophysical Lab. Instead, he partnered with bright people like Larry Finger, George Cody, Robert Downs, and others to anchor the data collecting. Often, we sparred with one another, at unpredictable times. He saw my work as incremental, which is what most scientific advances truly are. I saw his work as broad brush, not getting at the heart of problems. Either way, Hazen sustained having novel scientific ideas which he supported with his encyclopedic ability to read articles, understand them, and write about them with style.

         Harold Morowitz was a real original thinker and intellect. Working at a second tier university in northern Virginia, he struck me as a person who could work anywhere that welcomed complex thoughts. Harold knew the biochemical pathways and enzymes thoroughly, which we appreciated. He visited to discuss the experiments, and sometimes tension arose when hypotheses did not match results and findings. Both he and Bob Hazen were scholars, while the rest of us were soldiers in the laboratory figuring out difficult analytical problems. Fortunately, George Cody and Harold worked on the same plane and were able to match their talents to produce the detailed work on abiotic organic synthesis.

          Hazen and Morowitz’s idea was to use heat and pressure—non-biological hydrothermal chemistry--rather than biological enzymes to see if we could simulate the TCA cycle reactions. The TCA cycle (also known as the Krebs cycle) operates generating energy for cells in just about all known organisms. Some microbes are missing a piece of the cycle, but in general, the TCA cycle is at the heart of metabolism. Geophysical Laboratory staff member George Cody, former Geophysical Laboratory Director Hat Yoder and I, as well as Bob and Harold, postdocs Mark Teece, Jay Brandes, Tim Filley, Jennifer Blank, and Nabil Boctor, discussed how this could be carried out. Bob and his postdocs would seal simple organic reactants into gold tubes—1/4” in diameter and about 4 inches long--that served as reaction vessels.  Then, Hat Yoder would take the gold tubes and subject them to high temperatures (200°C) and high pressures in his laboratory’s apparatus that took up an entire room. He was used to doing experiments at thousands of atmospheres of pressure and at least 500°C. It was a challenge for him to reduce the pressure and temperatures to levels that would not completely burn up the organic starting materials. He would place the small gold tubes into larger metal cylinders that he referred to as “bombs” because if they were made improperly they could explode and had the power to shoot through pretty think steel walls. Fortunately, that did not happen with any of our samples.

We tried to create "life" with heat and temperature, 2002

         George and his postdocs would analyze the products of the reaction. George Cody is one-of-a-kind, often self-absorbed and oblivious to humans, other times thinking about the long-term vision for the Geophysical Laboratory and his colleagues. Cody is most comfortable at the console of his custom built NMR spectrometer. As he evolved from being a coal chemist to an organic geochemist to an astrobiologist to a generalist, his skills in analyzing complex data sets thoroughly distinguish his work. At parties, George often can’t leave his work behind. After a few glasses of red wine, he may regale his friends about hamiltonians (an obscure parameter measured by his NMR spectrometer), while his wife looks patiently on. When we worked together, I could always rely on George to huddle with me and figure out gnarly lab problems, personnel issues, and weird data. Mark Teece and I were to measure the isotopic biosignature in the products; Harold and the rest of us would interpret the results. 

Jay Brandes (l) and George Cody at his NMR, 2001

         Experiments were more complicated than we ever anticipated. Eventually, Cody and team members found a potential reaction that jump started a modification of the biological TCA cycle. This pathway, named the hydrothermal redox pathway, is not used in any extant organisms but may have been the ignition point for primary metabolism during the early evolution of living organisms. One of the keys to getting this pathway to work at all was to choose the correct metals (for example, iron) and their sulfide minerals as catalysts. The potentially critical catalytic role of such metallic catalysts may be a crucial link between geochemistry and biochemistry at the point of life’s emergence. Integrating all of this, they discovered that they were within one reaction of demonstrating a purely geochemical carbon fixation pathway that closely mimics the TCA pathways, but they were unable, ever, to figure out how to do the last remaining reaction non-biologically.

         Origin of life studies were being carried out across the NAI and internationally at this time (2000s). The RNA world hypothesis, promoted by Jack Shostack at MIT, had been a favored pathway for jump-starting life. RNA (ribonucleic acid, one of the molecules carrying the genetic code) can catalyze simple reactions, directs the construction of more complicated molecules like proteins, and holds heritable information. The problem with this model was figuring out how to make RNA molecules in the first place. One hypothesis was that meteorites that bombarded early Earth brought these molecules with them.

         Zita Martins and the organic geochemists at Goddard Space Flight Center were searching for the building blocks of DNA and RNA, nucleobases, in organic extracts of the Murchison meteorite, one of the most famous carbonaceous chondrites of all time. Zita was working with Danny Glavin and Jason Dworkin at Goddard, and her colleagues and PhD advisor in the Netherlands. Using a sophisticated type of mass spectrometry, she could detect nucleobases in some of the Murchison extracts. She was able to zero in on these unusual and complicated structures, essentially picking the “needles out of the haystack” of other compounds. We began a collaboration to measure the stable isotope biosignature patterns in these particular molecules. If they really came from outer space, these compounds should have an isotope biosignature pattern similar to other meteorite organic molecules. Alternatively, if these were terrestrial contaminants, they should resemble isotope biosignature patterns of biological molecules.

         Zita arrived with extracts in hand at the Geophysical Laboratory, and we were confident that we could readily measure the carbon isotope patterns based on the results she measured at Goddard Space Flight Center. Unfortunately, the analytical system I was using, a combustion-GC-IRMS system, combusts all carbon compounds in the chromatogram, which was loaded with a multitude of other compounds, mostly organic acids, as well as with trace amounts of nucleobases (Martins et al., 2008).

         We were able to devise a clever analytical scheme for our instrument that separated the organic acids from the nucleobases without any serious overlap. The carbon isotope biosignature patterns of the organic acids had enriched levels of ¹³C in them, similar to measurements others had made on these same types of compounds in meteorites. We were thrilled when we were able to measure a ¹³C-enriched carbon isotope biosignature for uracil, a component in RNA, in the Murchison sample. The two isotope biosignatures were consistent with an extraterrestrial origin for both compounds. We also analyzed uracil from the soil surrounding the location in Australia where the meteorite was found. The soil uracil had an isotope biosignature similar to terrestrial carbon—not at all like the meteorite uracil. This work supports one of the many theories about the origins of life. One of these theories holds that meteorites delivered organic molecules to Earth during its formation and the period when Earth was continually bombarded by incoming asteroids. Although it was known that amino acids (e.g.,  Engel et al., 1980; Martins et al., 2007) were common monomers in some meteorites, no one had ever found nucleobases.

         Eventually, the stable isotope biogeochemistry studies of the Carnegie team shifted in emphasis. In phase two of the NAI project at the Geophysical Laboratory, we began to study the isotopic compositions of ancient sedimentary rocks and stromatolites and began an ambitious field campaign in Svalbard, an archipelago high above the Arctic Circle in a project termed AMASE: Arctic Mars Analogue Svalbard Expedition. Both the NAI and AMASE endeavors required field trips to far flung places to collect samples from ecosystems of interest to astrobiologists.

Andrew Steele AKA Steelie

            With Wes Huntress as our new Director in 1999, we began a search to hire a replacement for Ed Hare—someone who would be a full time astrobiologist. Carnegie and the Geophysical Laboratory hire people in very different ways than universities. It is the sole discretion of the Director of the department to choose and negotiate with a new staff member. For the astrobiology position, we advertised widely and received a number of applications from interesting, qualified individuals. A short list was struck and about five people each spent a couple of days visiting the campus, giving a seminar, and trying to impress the scientific staff.

            At the time, I was involved in using a new time-of-flight mass spectrometer to identify unknown compounds in complex mixtures. The instrument, the Protein Chip Reader, could measure the coupling of an antibody with its antigen very precisely. I had heard about a young man at Johnson Space Flight Center who was developing a similar system—except miniaturized—for flying on an upcoming Mars mission. He also heard of what I was doing and wrote me an email asking to visit the Laboratory. I was excited by the prospect, asked for his CV, and invited him to come for a seminar. Unbeknownst to him, his CV was circulated to the astrobiology hiring committee. We considered him a potentially viable candidate. Andrew Steele was officially on our radar screen.

            Andrew was, by then, working in England, so flew over to the States the weekend before his seminar to get adjusted to the time change. I met him briefly before his Monday seminar, telling him, “Hey! Do you know we have a staff position open for an Astrobiologist?” He did not. The news sent him into a bit of a panic, because Steele is usually informal in his mannerisms, dress, and speaking style. Apparently, he purchased a new outfit, updated his talk, and practiced it again and again before arriving at the Lab for his “visit” early Monday morning, which morphed into an impromptu interview. His combination of microbiology, meteorite geochemistry, technology, and Mars science was a perfect fit for what we were looking for. An offer quickly followed.

Steelie at the 9:30 Club, Washington DC

            Andrew—Steelie, as he is known to almost everyone, looks the part of a 1990s British rocker. In fact, he is an accomplished guitarist and composer of rock music, playing and singing in a Takoma Park band. His light brown hair reaches to the middle of his back, or is frequently up in a man-bun or back in a ragged ponytail. Wearing jeans purchased at a boutique shop in London and a t-shirt with science logos, Steelie can light up a room with his outward enthusiasm. He wears his personality and feelings on his sleeve, however. When he’s in a bad mood, it shows. When he’s deep in thought, he paces, looking at the ground, muttering to himself about thermodynamics and Mars.

            I was barely 13 years old when Steelie was born in January 1965. When we traveled to conferences, NASA meetings, and fieldwork, we looked like an unusual pair. Once—just once—in an airport rental car lot, a stranger said to him, “Your mother is waving at you over there.” That comment resulted in endless teasing. I was not old enough to be his mother, but earned the nickname of “Ma.” While he liked to say he thought I was “matronly” when he first met me, I enjoyed saying about him, “Yeah, he’s my son, living in the basement, doesn't have a girlfriend or a job, plays on an old Atari video game all day.” The razzing continues to this day.

            Steelie hit the ground running at the Lab and built a strong team of young postdocs and students who adored him and his unconventional style. People came from around the world to work with him. He set up his first lab in Ed Hare and John Frantz’s old labs, shoehorning in autoclaves, microbial culture apparatus, DNA identification instruments, and sophisticated microscopes. He was known for working odd hours. I’d see him slink by my office around 11 am, backpack slung over his shoulder, often laughing. He worked until late at night, sometimes regaling his colleagues with emails at midnight. Steelie had never been responsible for lab personnel before. Sometimes he loved the job, other times he found it a bother.

            Often, he was late for lab, committee, and informal meetings that he himself had set up. Finally one day, fed up with this, his lab group and I “decorated” his office with thousands of Styrofoam peanuts. When he saw the mess we created he was furious and let his lab mates know, in no uncertain terms, he was angry with their childish behavior. I let him know that I was the mastermind of the prank, and that if he wanted grown up behavior, he should be on time like a professional adult. We glowered a bit, then burst out laughing. I can’t say he completely changed his ways, but he grew more “adult like” and commanded the respect of his peers and lab group.

Styroform peanut crew, Steelie's lab

            Steelie’s first field trip was with my lab group who were investigating the effects of chicken waste (i.e., chicken &%*t) on the ecosystem. As part of this trip, we used seine nets to sample small fish from rivers that had been potentially polluted by chicken waste. Steelie came dressed in shorts wearing sandals. On his first attempt at fish seining, he lost one sandal in the mud. The remainder of the day he wore one shoe. He’d also forgotten to bring his wallet and drivers license, something we learned was more common than not. Consequently, when we went out for beers at the end of the day, the waitress refused to serve him. 

Steelie missing his shoe, 1st field trip

            Steelie’s next field trip was the 2003 expedition on AMASE. In Longyearbyen, he purchased a pair of fancy red hiking boots, which gave him huge blisters when he climbed Sverrefjell volcano for the first time. I joined the AMASE team in 2004, and by this time, he became skilled at organizing Artic fieldwork and finding signs of life on seemingly barren rocks. Never ever one to give up, Steelie went on to become Chief Scientist and an accomplished Arctic explorer over the years.

Steelie doing science in the Arctic

         Steelie is one of my Science Brothers. Now that we live and work thousands of miles away from each other, when we call the other answers the phone “As I live and breathe!” I watched over his daughter when his second child was born. He mentored my son Evan when Chris and I moved to California. Steelie was one of the first people I told about my ALS diagnosis. I was one of the first he told about his mother’s passing. I may be more matronly than ever. His hair and beard are tinged with gray, but we’ve got a firm hold on life and science. 

Steelie and Marilyn, Merced, 2014

A ride on the Vomit Comet

            We’ve all watched those space movies—Sandra Bullock floating around trying to repair a space ship, her hair twirling around her head, waving herself around the universe. It’s as fun as it looks, which I found out in 2004 on a trip on NASA’s Vomit Comet. In order to train astronauts for the feeling of zero gravity, NASA has a special plane taking off from Johnson Space Flight Center near Houston, Texas. In order to achieve zero gravity, the aircraft, a large C-130 cargo jet aircraft, follows a parabolic flight plan going up in an arc followed by descending in a similar arc. During the upward climb, gravity is about double Earth’s gravity; on the downward trajectory, gravity goes to zero.

            My opportunity to fly on the Vomit Comet was made possible by working with Jake Maule, a postdoc working with Andrew Steele. Jake, now a physician at Duke University Hospital, is a trim, sharp-looking Brit who had dreams of joining the astronaut core. His PhD is in medicine, so he was looking to use that training combined with an astrobiology theme to be attractive to the very competitive NASA program for selecting astronauts. Jake and I were both interested in immunology at that time. I had purchased an instrument capable of making the types of measurements that can detect complex diseases like HIV-AIDS. The instrument, an ELISA reader (enzyme-linked immuno-sorbent assay) measures the amount and strength that antibodies have in binding to the molecules, antigens, they are trying to remove from harming our bodies. 

Jake Maule, Arctic, 2005

            Jake’s idea was to use the ELISA reader to find out whether and how antibodies and antigens hook up together without the benefit of gravity. He asked to borrow my instrument. I told him, “OK, but you have to take me with you!” He thought about it briefly, and agreed. We flew down to Johnson Space Flight Center for 2 days of training. After a morning of lectures, we went into a space simulation chamber that was evacuated leaving almost no air, but all was fine because we were wearing oxygen masks. The chamber was then filled with nitrogen gas—which does not support life—and we were asked to remove our masks. It took me only 20 seconds to feel the effects—I was unable to count to five! My mask went right back on.

            Jake and I practiced our experiments in a lab on the ground. We planned to fly 40 cycles alternating between zero gravity and two-times gravity (2-G) during our 3 hour flight. Each cycle lasted 20 seconds—barely enough time to complete the manipulations needed. The morning of our flight we were given two medications to help—Dexedrine and scopolamine-one to keep you awake and the other to keep you from getting airsick. Donning NASA flight suits, 15 scientists, a flight supervisor, and the flight surgeon entered the plane. Excitedly, we set up our experiments. Ours was inside of a newborn baby’s Isolette, a plastic box with armholes for two people to attend to a premature infant, which kept our supplies from floating around the aircraft.

            We were seated for takeoff, then at 10,000 feet we moved to our workstations, where our feet were placed under straps so we wouldn’t float away. When we were about to enter zero-G, special lights flashed on. Then, as we switched to 2-G, the flight supervisor shouted, “Feet down! Comin’ up!” We heard that phrase more than 40 times.

            The first zero-G experience made your stomach do a flip-flop. Your hair raises up, your equipment floats around. Wow! Then, all too soon, you feel 2-G making you twice your body weight. A slight movement of your head and you felt nauseous, even going so far as to cause vomiting. On the second cycle, we began the manipulations. My skills working at sea on ships tossed around by big waves trained me for this work. Opposite to me, Jake was turning a bit green. The flight surgeon floated by, offered him a barf bag, wrapped it up, and then went on to the next scientist who needed some help. I’m proud to say my stomach remained in check.

            After 40 cycles of zero G, Jake and I unplugged and floated for the next couple of parabolas. The feeling of weightlessness, even for 20 seconds, is something my body has never forgotten. The ability to float in air, even fly, is something we only dream about but never experience. The trip on the Vomit Comet let my soul soar!

            Because I was a trooper on the flight, the pilots invited me to sit in the jump seat just behind them when we were returning to Johnson. What an eye opener!  First, I saw how close we were to another airplane and how the pilots handled that. Then, a warning light came on in the panel of instruments on the plane’s dashboard. We were all connected via headsets, so I could hear them discussing the meaning of the orange light. Apparently, it had to do with the functioning of one of the two jet engines. After we safely landed, the plane was taken into a hanger for maintenance to figure out what was happening with that engine. Turns out that it needed to be completely overhauled. Our 2^nd flight was cancelled and the Vomit Comet was out of commission for months.

            Our experiments were successful. We determined that antibodies and antigens had no problems working in the absence of gravity. Although humans evolved with the benefits of a gravitational field, our biochemical systems could adapt to spaceflight.

"Be occupied with or focused on things and issues that are of interest, importance, and concern to you"

Still crazy after all these years...Mariposa, 2019

“Be occupied with or focused on things and issues that are of interest, importance, and concern to you. Remain passionately involved in them.” Morrie Schwartz

Today I took possession of a machine that sits on a small table next to my bed. There are plastic hoses attached to it and a set of straps that fits over my head. The straps hold a small mask that fits over my nose. When the machine is ON, it will provide extra puffs of air to expand my lungs to full capacity when I’m sleeping. Even though the mask doesn’t cover my mouth, when the machine is on I’m unable to talk.

It will take willpower to get used to this thing. I’ll give it my best shot.

It’s been a hell of a roller coaster couple of weeks. I’m now a Lame Duck faculty member. When I left my last two positions at the Geophysical Lab and UC Merced, I remained in touch for a year, keeping instruments going, people happy and employed. Having two jobs at a time is real work—make no mistake. I’m trying this time to have a smoother transition into retirement. If I follow Morrie’s advice, which I do whenever possible, I need to keep focused. I am. And will continue to be.

What makes this more difficult than it should be is subtle. I was very close to losing something very important (and dear) to making my last days as a professor important and relevant. When I had to ponder that potential loss for several days, it made me realize even more that I can’t fight all the battles and solve all the problems that were the hallmark of my persona for the past 40 years.

“Just let it go. Inch by inch. Just let it go. Inch by inch. One day you’ll see.” India Arie

I’ve been given a reprieve—but this was a wakeup call. What has been important and concerning to me is necessarily going to change. I am thankful to have the opportunity to close out my time at the University as best as I can manage.

“Resist the temptation to think of yourself as useless…Find your own ways of being and feeling useful.”

It’s a constant struggle beginning each and every day to find ways of being useful that don't completely exhaust me. Forget all physical activities—I need help with everything. Mentally, I’ve got to pull things together.

I was asked last week by a student how the hell I managed to build a lab, start an Institute, move to a new city, teach, write grants, and have a life with the overwhelming burden of ALS. I answered that it took planning and breaking these tasks down into small manageable bits. I’ve never been a person who is “overwhelmed”. Chris and I are pretty steady, get-shit-done sort of people. We’ve been getting shit done. The conversation made me realize that I need to take stock of what I have accomplished and start to think of the next phase. What does “useful” look like in my future?

I can order food from Amazon for my 92-year-old mother, but I can’t buy her fresh milk, as she’s in New Jersey. I can buy birthday presents online, but it ain’t easy to stroll through shops and pick things out. I can find easy, tasty recipes online for Chris and I to cook, but I can’t put a baking dish in the oven. I can mix Manhattans (bourbon and vermouth with a cherry), but I can’t drink more than half of one. I can read, correct grammar, and suggest editorial changes, but the time is over for starting anything new. 

I can help save for his college education! Sheri, Mike, and baby Travis (my nephews)

I can write my feelings down in this blog. You readers help me when you read and comment. It makes me feel useful.

“Don’t assume that it’s too late to become involved or to redirect your interests.” Morrie Schwartz

When I faced the possibility of shrinking my final University aspirations, it became very real that I need to take more effort to redirect my interests. July will be here before I know it. The Institute will either go into mothballs for a year, or someone will step in (and up) and see that it continues. I’ll easily transition off any faculty committees. (I’d be weird if that weren’t the case.) The final remaining piece is the laboratory. I’ll need to say good-bye, leave it to others who can figure things out.

At lunch with a friend last week, she asked how my painting was coming along. She’s a painter herself—and quite a good one with stunning abstracts that pop out with color and feeling. I mentioned how it was harder to hold a brush, couldn’t reach far, etc. She listened patiently and hoped I’d figure it out, in so many words. I will.

Chris and I need to figure out the travel piece, which is a movable target. Come July, we’ll host family for a couple weeks, then time will yawn on. We’re hoping to spend long times on the coast at Sea Ranch. Reading books, calling friends, and breathing fresh sea air.

Our friends are stepping up. In mid-February, we’ll be hosting two old friends that I’ve known since Chris and I met and a former student/postdoc and her husband. They’ll join us on the Mariposa “campus” helping making meals, helping schlepp me to Yosemite or wildlife refuges in the Valley. I hope they’ll contribute to Morrie’s next bit of advice.

“Take in as much joy as you can whenever and however you can. You may find it in unpredictable places and situations.” Morrie Schwartz

I tell my mother every time we talk, “Remember, laughter is your best medicine!” I gotta have this on my mind every day. ALS medications do a bit, but it’s that laughter and lightness that makes the day tolerable.

Chris and I watch funny movies, tell stupid Dad jokes, quote Monty Python, and try how we might to keep laughing. I will do this. We will make these days as laughter filled as we can. If there are some troubling times, I will remind myself of Morrie’s sage advice to find joy in new places.

And when I concentrate on things like the Salton Sea, the triple quad mass spectrometer and mass fragments, painting, hosting, and laughing, I’ll try to conquer that damn breathing machine so I can laugh as loud as I possibly can.

Australia Part 2: Social interactions and stories

Giff Miller, Richard Tax, Marilyn, Sean Pack (standing); Geoff Hunt (rooftop), Mulan area 1999

  

       As we wound our way to the Top End, we experienced social norms very different than those in the United States at that time. For example, it was surprising to almost everyone that I was the scientist leading the trip, not my husband. In the town of Daly Waters, we attended a comedy show in a restaurant and heard many racist and anti-gay jokes. In indigenous people's communities, we saw poverty, alcoholism, and segregation, typically with a white couple running the show through the local gas and food store. The availability of fresh food in the Outback was minimal—frozen kangaroo tails were considered a delicacy. Chips (French fries), sweets, and white bread (also frozen) were about the only groceries available to the community.

            Working in remote Aboriginal communities requires several years of planning. We obtained permits for our studies in the Lake Gregory region of Western Australia. Getting there wasn't easy. Working with local people required building trust and respecting local customs. Our relationships with the people of Mulan, the community near Lake Gregory, were very good.

        On my second trip to Australia in 1998, my family and I started our voyage in Perth, drove north along the Indian Ocean coast, then inland to Halls Creek, a mid-size town in Western Australia. Our destination was the village of Mulan, an Aboriginal outpost with a population of about 200 people. We were headed to this area because Mulan was on the shores of Lake Gregory, a 400 square mile lake that has been accumulating sediments for thousands of years. Mulan wasn’t on any of the maps that we used to get us to the Lake Gregory field area. Giff Miller had sent a cryptic email that said, “Turn right about 30 kilometers after you pass through Billaluna. We’ll be camping about 10 kilometers out of town on a creek. You can’t miss it.”

            We drove from Halls Creek, past the Wolfe Creek Meteorite Crater to Billaluna, a town with several shops and a gas station. There, we asked where the road to Mulan was, but we asked in a way that was destined to take us in the wrong direction.

         We did not realize that indigenous people never answered “no” when asked a yes or no question. We asked, “Is this the road to Mulan?” The answer was, of course, yes. Our family of four, mom and dad with our two kids, headed down a dirt track that got smaller and smaller. Just outside of town, we passed a hitchhiker and without much thought, offered him a ride. He was heading in the same direction as we were, but we didn’t notice until he hopped in the car that he was carrying a rifle. Perhaps this wasn’t the smartest thing we’d ever done. 

         After a few kilometers, we came up to a group of Aboriginal hunters, and our rider thanked us and took off. The hunters had set fire to the area on the left side of the road in order to drive game to the other side where they would shoot any bustards--turkey-sized birds--or kangaroos, both of which were considered delicacies. It was our first time driving through a bush fire, but not the last. When we let off our hitchhiker, the road diverged into three directions. Chris pointed to the left fork, “Is this the best way to get to Mulan?” The answer, of course, was yes. Chris headed the jeep down a one-lane dirt track. Within a kilometer or two, the road had diverged again. We stopped, thought about it for a moment, then took the left fork. Shortly, the road started to fade out with thorny acacia bushes covering the way. We had reached a dead end.

Painting of Lake Gregory and Serpent

         Fortunately we had food, water, and enough fuel to camp out if we were lost—and we were. Carefully, we turned the vehicle around and retraced our steps. In 1998, I did not have a GPS unit so were traveling on our own with maps. After returning to Billaluna, we stopped in the store, this time asking the white proprietor how to get to Mulan. He directed us back to the Tanami Track and told us to look for a primitive sign and an even more primitive track leading to Mulan. Near 5 pm, as the sun was low in the horizon, we finally turned off on the track that took us through sand dunes and swamps to the village of Mulan.

         Over the years, I met many indigenous people, even working with them in the field. I went many times through the village of Mulan, 40 kilometers off the Tanami Track in Western Australia, but that first trip influenced my son to become a medical professional. Years later he reflected on this trip:

“I traveled with my family through the Australian outback in search of the small Aboriginal town, Mulan, where my mother conducted fieldwork, 8 hours away from the nearest paved road. After years of abuse from the Australian government, the village greeted us with wary skepticism. Mulan hosted high levels of chronic illness, drug and alcohol abuse, and impoverishment. The village leader, Whiskey, took us in and we exchanged ideas on wildlife and climate. Throughout our stay, what impressed me more than the accumulation of 100s of years of passed down knowledge was the distinct and overwhelming respect the community held for him as their leader and, more importantly, as their healer. He treated everyone with the utmost kindness and kept an open ear for all who sought his counsel. The degree of trust they had in him inspired resilience that pushed them through times of drought and illness. Observing Whiskey made me realize how one person can make a difference in the lives of others. The strength he inspired in his people allowed them to turn the Australian outback into a home where they could grow for generations.” Evan Swarth, December 2018.

Marilyn and Evan on the road to Mulan, 1998

         We drove out of Mulan with Whiskey’s directions—over a sand hill, through a creek bed, then over a sand hill, you’ll see them on the right, he said. We took off confident we’d be in the camp within a few minutes. No problem with the first couple of sand hills and creek beds, but no sign of Giff or John. Then the road forked. We got out of the vehicle and looked for recent tracks, but the sun was now well below the horizon and it was getting dark. We chose the left fork heading into a vast open plain dotted with the outlines of gum trees. Suddenly, there in the distance we saw the bright orange glow of a campfire! The relief was palpable. 

         We’d made it or so we thought. As we drove closer, the orange glow grew larger—but it was the rising moon. Disappointment lay heavy in the vehicle. Chris and I kept an upbeat tone. But it was 9 pm, pitch black outside. The kids were hungry, and we were beat. We pulled off the road under a gum tree, pitched our tent, heated up some baked beans, and called it a day. The kids slept in the car.

         Where was Giff? Would we ever find the camp? The next morning we packed up camp, and with determination, continued on the track. Within 20 minutes, we ran straight into a small caravan of field vehicles driven by Giff, John Magee and Jim Bowler. Relief flooded over me. We’d actually made it, this time. After spending the day collecting plants, we headed at last to the camp, another 10 kilometers from where we’d parked the night before, far from the few sand hills past Mulan. 

Nancy Tax (Richard's wife), Lake Gregory painting

         That first field season in the Mulan and Lake Gregory area was a good experience for learning how to incorporate a whole new field area into a study. We had originally thought that we could take sediment cores from the center of Lake Gregory, a sizeable lake in  native territory. We were naïve in this thought because the community had no boats and forbid sampling sediments in any part of the lake. When we thought about this, we realized that the Mulan people’s dreamtime stories included a serpent coming from the center of the lake, who morphed into the tribe that occupies the land today. To drill into the lake would in essence disturb the sacred ground—a religious area strictly off limits to geologists.

Richard Tax, Senior Lawman, Rainmaker, and Artist

         Collecting plants and eggshells was no problem for the elders in Mulan, but taking soil samples was another matter, because soil meant earth, meaning their land. In 2001, we wanted to take cores of sand dunes in the Lake Gregory area around Mulan. To do so, we were assigned a “senior lawman” to travel with us to make sure we did not violate any sacred sites. Monday morning we picked up Richard Tax, who was accompanied to our vehicle by his wife, Nancy Tax. Richard was dressed in an older, buttoned shirt, some three-quarter length pants, and a pair of seemingly ill-fitting shoes. He reeked of tobacco, sat quietly in the back seat sans seatbelt with his lunch in a tin container.  We took off going places, we learned later, that Richard had not seen since he was a boy. As we crested one particularly steep sand dune where everyone, not just me squealed, we heard his seat belt click on. Together we were on a once in a lifetime ride into wilderness where the closest inhabitants were 100 kilometers away in all directions. The power and beauty of the landscape filled us with quiet awe.

         Tax became a member of our team on Wednesday of that week. When we stopped to pick him up, he leaped into the vehicle, nodded good morning, clicked his seat belt, and we were off. At lunch time, we would park under a gum tree, gather some twigs and make a small fire to heat the Billy for tea and Jaffles, heated sandwiches filled with yesterday’s leftover dinner, slices of cheese, and pepper sauce, melded together over the fire. Student Sean Pack offered Tax sugar for his tea with the phrase “Say when!” We watched as more and more sugar was dumped into Richard’s cup, finally realizing he had no idea what “Say when” actually meant. The syrupy tea was dumped and everyone laughed. 

         On our last day with Richard, we stopped and took a group photo. It is said that indigenous people of Australia don’t like to be photographed, but that did not seem a problem. We shook hands warmly as we drove out of Mulan, knowing we’d had a cultural experience and glimpse into the life of a native Australian that almost no white Australians ever have. When we departed via the town of Balgo, stopping at the local art shoppe, we were surprised to learn that not only was Richard Tax a valued senior lawman, but he was the Rainmaker of the community, a man who could put a spell on us if we’d misbehaved! He was also an internationally recognized painter with tourists flying into Balgo to purchase his artwork. His painting of people sitting around a campfire hangs on the wall of my home office as I wrote this. 

Richard Tax, abstract painting of people (Xs) around a campfire

Wolfe Creek Meteorite Crater or the Rainbow Serpent’s ascent

            The samples we were ultimately able to collect in the Lake Gregory area weren’t good enough to provide a robust climate signal. Giff, John Magee, and I had another idea. We thought the Wolfe Creek meteorite crater just north of Lake Gregory might provide us with laminated sediments, if we were to take a core in the very center of the crater. Wolfe Creek meteorite crater is part of a national park of the same name. We obtained permission to sample the sediments inside the crater from the National Park folks, as well as the senior lawmen from the Aboriginal community that resided in Billaluna to the south.

            An international team was assembled. Bev Johnson, postdoc Matthew Wooller, and two students of Bev’s from Bates College joined Giff, John Magee, and scientists from Australian National University at the campground just outside the crater. A sizeable drilling rig had been hauled up on a trailer from Canberra. Using a system of ropes and pulleys, the rig was carefully lowered from the east rim down to the crater floor. After a couple of days of testing, we took our first few meters of core sediments. The floor of the Crater contains plants that are specially adapted to that environment. At its very center, there are small ponds 1-2 meters in diameter that are filled with aquatic plants and slimy microbes. It is without a doubt a surreal place that exudes a feeling of cultural importance.

            On the third day of drilling, we were relaxing around the campfire, discussing the day, when a man walked into our camp uninvited. He was about 50 years old, wearing a pair of grey woolen slacks, a short sleeved white sport shirt, and a skinny tie. At first glance, I took him for a religious missionary of some sort. We said hello to him, then he spoke.

Mat Wooller, Giff, Marilyn, and John Magee, 2001 Wolfe Creek campsite

            “I’ll have to ask you to cease and desist from your drilling operation in the Crater, or I’m afraid I’ll have to put you under arrest,” he announced somewhat sheepishly. He was from the government council in Halls Creek, 158 km north, the nearest major town. “We’ve had complaints from the local community down here. You need to stop.”

            We were stunned—almost speechless. Giff was the first to get control, “But we’ve got permits from the National Park and the community. Who complained?”

            “I can’t really say,” the government fellow answered, “but this is a sacred site and it can’t be violated. I’m afraid there is no choice but to stop your work and leave the crater.”

            I pictured myself in a jail cell in Halls Creek, sharing the space with women who were sleeping off a night of heavy drinking. It wasn’t appealing. After a twenty-minute conversation, we obtained more details and discussed appealing our situation to the government office in Halls Creek the next morning. Giff, Magee, and I packed overnight bags and drove into the town after breakfast. We spent time going from government buildings to community spaces speaking with both white and indigenous people leaders. No one was sympathetic. The area was closed to drilling and that was that. Eventually, we learned how to get in touch with cultural leaders in the Billaluna—not the senior lawmen that we’d gotten permission from.

            Two days later, three older members of the community came to our campsite and listened to our story. Most geologists in Australia are economic geologists searching for mineral deposits to make money. We were simply doing research—and spending money. We tried to make our case, but continued to be denied.

            We learned from a government anthropologist that the Crater site was so sacred, even the local community did not know its full importance. We gleaned that the Crater held their answer for the origin of their people. One of their enduring stories is that the Rainbow Serpent emerged from the center and created Sturt Creek, an important landmark. We’ll never know the full story because its written record is sealed and never to be opened by any but the indigenous people of the area.

            Mat Wooller and I spent a day collecting plants and surface soils in the Crater, while the drill team hauled the rig back up the side and out. We had tried but had run smack into cultural norms that we don’t have in the United States. Giff and John cored a sand dune just outside the rim. We made the best of a bad situation. That can easily happen in any research endeavor. I learned that it’s best to undertake complicated projects with an open mind. Fortunately for us, we were a strong team and able to lick our wounds and continue on with our work in other areas.

Inside the meteorite crater, 2001

            The indigenous people of Australia have gone through near annihilation during their first couple of centuries of contact with Europeans. I treasure the times I was able to visit their lands and see first hand their view of their history and culture. Both Giff and I purchased many Aboriginal paintings during our trips there. They mind me, daily, that there is still a world out there that doesn’t depend on tweets and television.

Extinction and Climate change in the Australian Outback

Giff Miller and Marilyn, Mulan, 2000

         The Australian Outback is known for its hot, dry conditions, but it hasn’t always been that way. Geologists look at sediments around lakes that are now dried out and can tell that in the past, these lakes were filled with water and surrounded by animals and humans. One of the goals of my study of Australian climate has been to figure out the wet-dry cycles that have occurred over the past 120,000 years. Also, I asked the questions: Did early humans have an influence on the amount of rainfall that fell on Australia? Are the current dry conditions in the Outback related to human influences?  

            When people first came to Australia about 55,000 years ago, the landscape was very different from today. The first Aboriginal settlers came from Indonesia, during a glacial period when sea levels were much lower than they are now. Primitive boats could easily cross the distance between Australia and the northern islands. Within only a few thousand years, people had settled along most of Australia’s vast coastlines as well as the interior that we know today as the Outback, a dry, hot, extreme environment with limited plant and animal life. When humans first arrived, the continent was home to many species of giant marsupials, monotremes (mammals that give birth from eggs like the platypus), birds and lizards. These large beasts are called megafauna. In Australia, the megafauna all went extinct a few thousand years after humans came to the continent.

Genyornis (left) and emu (right)

            What happened to Australia’s megafauna? Scientists have been studying the causes of major animal extinctions in Australia and North America for many decades. Typically, paleontologists (scientists studying past animals and plants) look for fossils, records of pollen from ancient plants, and study the sediments to figure out the living history of an area. In Australia, there are rich beds of fossils that have been recovered in caves, around lakeshores, and in riverbank sediments. Because Australia has been hot and dry for so long, the sediments from the Outback don’t have pollen in them anymore, so scientists have little idea what kind of plants used to live here. 

Artists rendition of early inhabitants of Australia

            There are a few ideas about what happened to the megafauna. Some scientists believe that they went extinct as the climate changed naturally. They believe that after a cold glacial period, they never came back. Other scientists think that hunting of the megafauna slowly depleted their populations until they no longer could survive. The idea that my colleagues and I have been investigating is whether human use of fire was the main reason for wiping out the megafauna.

            How can fire destroy almost all of a country’s large animals? What does fire do to the plants and the climate? Can human actions like burning the landscape, as an aid to hunting and food gathering, change the climate of an entire continent?

Bush fire, Lake Gregory area, Marilyn in foreground

            Earth’s climate has changed drastically over time. In the past 2 million years, the climate has swung between ice ages and hot houses roughly correlated to subtle differences in how the Earth revolves around the sun. These differences turn out to be cyclical in nature, occurring on periods of 25, 40 or 100 thousand years called Milankovitch cycles. There was very little detailed understanding of the periodicity and magnitude of these cycles until scientists began measuring very small changes in isotope patterns found in carbonates in marine sediment cores. As more and more sediment cores were brought into isotope labs and measured, scientists began to compare and correlate isotope patterns across major ocean basins.

            Oxygen isotope patterns in a sediment core are “wiggly lines” shifting as sea ice accumulates and global temperatures increase or decrease. Using radiogenic isotopes, like uranium, some of the cores were dated, then scientists matched the isotope variations in the wiggly lines allowing them to provide a global pattern of climate change over time. It became evident from this work that although climate changed all over the globe at the same time, there were some differences depending on the geographic location of the core. The work I conducted in Australia was concerned with continental scale climate change, which was influenced by global processes but had many more factors influencing it.

        Because there are no laminated sediments in the Outback region of Australia, climate science was at a standstill. There needed to be another method for learning about paleo-temperatures, vegetation, and rainfall amounts as a function of geologic time. In the early 1990s, my colleague at the Geophysical Lab, Ed Hare, and Allison Brooks, an archaeologist at George Washington University, had a new idea based on finding beads made from ostrich eggshells in archeological excavations from early human sites in southern Africa.  Ed, a geochemist, and Allison worked together and developed techniques for dating the fossil eggshells using amino acid racemization methods described previously.

            As opposed to bones or teeth, eggshell holds onto its protein matrix and is not affected by geochemical changes even over hundred of thousands of years. It seemed to be a good bet that fossil eggshell would hold onto its isotope signals as well. Isotope biogeochemists in South Africa experimented with modern ostrich eggshells to see if carbon isotopes in ostrich eggshells hold a signal of the bird’s diet at the time it laid its egg. They did. 

Fossil emu and Genyornis eggshell pieces

            In 1991, Beverly Johnson, then a PhD student with Gifford Miller at the University of Colorado, came to the Geophysical Laboratory for several months to pilot a study on stable carbon and nitrogen isotopes in fossil and modern flightless bird eggshells (e.g., ostriches and emus). The work turned into her PhD dissertation and began a 28-year project that I have continued with Miller. Beverly managed to locate eggshells from farm-raised ostriches in the United States, along with their ostrich chow diet (Johnson et al. 1998). She also field collected ostrich eggshell from South Africa to calibrate the carbon isotope differences between diet, carbonate, and organic shell proteins. Her work on Equus Cave, South Africa, determined changes in vegetation, rainfall, and temperature over the last 17,000 years.

            Giff, a former postdoc working with Ed Hare, is a geologist with a natural inclination towards chemistry. His lab at the University of Colorado was housed on the bottom floor of a post-war brick building with aging lab benches. The shelves of his lab were packed with carefully labeled boxes of samples he’d collected in Arctic, African, and Australian localities. A couple of homemade amino acid analyzers hummed away on the benches, churning out measurements of the ratios of D- to L- amino acids (i.e., amino acid racemization) that Giff uses to date most of his samples. He typically has two or three graduate students in his lab at any one time. They keep the instruments going, periodically replacing separation columns and detectors. The lone sink in this lab sits adjacent to a fancy espresso coffee machine that pumps out brew at all hours. A table in the middle of the lab serves as a meeting place for visitors like myself and is a daily gathering place for Giff’s lab group.

            Being in Boulder, the Colorado team was usually casually dressed in Patagonia gear or specialized bicycle clothing after they’d taken a 20-mile ride up and down the Flatiron mountains adjacent to the campus. Giff is an especially stylish fellow both at home and in the field. In the 30 years we’ve worked together, he’s transitioned with grace from having almost an eternally youthful appearance to a distinguished salt-and-pepper bearded senior scientist.

         As Hare and Brooks work was being completed, Giff was starting a new collaboration with geologist John Magee and others at the Australian National University in Canberra. Emu eggshell and eggshell fragments from the extinct fossil bird Genyornis were plentiful in sand dune deposits throughout much of the arid interior of the Australian continent. Genyornis was a two-meter high flightless bird endemic to Australia. Like the emu, Genyornis was very heavily built and, as a result, were not the fastest movers. The large bird had powerful legs, tiny wings, an enormous beak and hoof-like claws. Fossils of Genyornis bones and eggs have been found throughout the south, west, and east Australia.

Field vehicles, 2006--We always had two

            It’s not easy to find fossil eggshells—small fragments 1 centimeter in size—spread out over the vastness of the Australian Outback. Giff and John Magee became experts in this “sport”. In the field, Miller is a wizard taking advantage of modern GIS technology to find promising deposits. Year after year, he and others combed sand dunes, head bent down, hands in pockets--slowly walking for hours to find small fragments of eggshells. Wind, over thousands of years, exposes the eggshells leaving them on the sandy surface. In a good day we might find 10 different places with 20 or more eggshell fragments in each. At the end of the day, we always uncorked a good bottle of red wine, cooked a meal of roasted Chook (that is chicken) or lamb over a campfire, and worked on the day’s field notes.

            In 1994, Beverly, now a postdoc, Giff, and John Magee joined my family for my first trip to Australia. My son was 3 years old and just recovering from a nasty round of chickenpox. My daughter, 7 years old, was very interested in animals and plants. My husband served as driver, campsite manager, babysitter, and principal ornithologist. We traveled from Adelaide, in Southern Australia, all the way north to Kakadu National Park, almost in Darwin, NT, and then back again, a ~6,000 kilometers roundtrip. All of the fieldwork was in remote regions of the Outback where we pitched a tent and prepared meals over a campfire. I collected plants and soils along the transect, learning to identify new species in the different regions of the continent. 

Evan (foreground), Marilyn, Giff, Bev, Lake Eyre 1994

         That first year we learned a lot about traveling, camping, and doing fieldwork in Australia. When my family split off from the seasoned team led by Giff and John, the sense of adventure was high! Set loose on an entirely new continent with a vehicle that could go anywhere, we took off on the Oodnadatta Track towards Alice Springs. Our first night was spent in a small caravan park in our tent. We ate canned beans for dinner and called it a day. Around midnight, we were awakened by loud voices and shouting from the adjacent Aboriginal community—our first subtle lesson on how this group gets along in Australia.

         We reached the outskirts of Alice Springs in a few days again setting up a camp with just our tent, no chairs, no tables, no pillows, no nothing. Looking around the caravan park, properly dressed older couples were having afternoon tea on a table laid with a flowered cloth, china teapot, and real teacups. They were seated on sturdy folding chairs in the shade of a gum tree, well out of the red dirt carpeting the caravan park. The next day we drove into Alice to the K-Mart in town and purchased a small folding table, two chairs, some pillows, and proper plates and cups. We stopped off at Woolworth’s supermarket and picked up fresh lamb chops, onions, and meat pies, along with a slab of beer and several bottles of decent red wine. Quickly, we learned that the men take the meat and onions to the Barbie, chat with each other as they cook, and the women remain in their camp with the children.

Dana and Chris sampling a dead emu, 1994

           The 1994 trip was my first international field expedition. I did not have proper plant import permits from the United States Department of Agriculture, so when we returned to the United States, my plants were confiscated at the border. I learned my lesson. Through contacts at the Smithsonian, I obtained a permit and after a nervous month, all of my samples entered the United States and were delivered safely to my lab. I brought back 250 plant specimens and over the next year we analyzed their carbon and nitrogen isotopic compositions. Grasses in Australia shift from C₄ metabolism in the North to mixtures of C₄ and C₃ grasses in the very south. Acacia species, both shrubs and trees, and eucalyptus trees are C₃ plants. In general, the vegetation in Australia has mixtures of grasses, Acacia, and eucalypts with variable proportions of herbaceous C₃ plants and chenopods. Our goal was to determine the extent of C₄ grasses in an Australian animal’s diet.

         Because we were ultimately studying the diets of emu and Genyornis, my field collections centered around two things: the general vegetative landscape and potential emu diet. Emus consume the seeds and flowers of all plants except eucalypts; they sometimes eat whole leaves and consume fruits when available. Without question, emus will also eat any insect or lizard that they can catch, which augments their protein intake substantially during the nesting season, particularly in arid areas. With subsequent trips in 1998, 1999, 2000, 2001, 2006, and 2008, I amassed more than 1000 plant specimens from all over the continent where annual precipitation amounts ranged from less than 100 mm per year to well over 4,000 mm per year. Precipitation affects the ability of plants to fix carbon dioxide during photosynthesis and regulates the cycling of nitrogen containing nutrients in soil.

       Fortunately by this time we were using a new elemental analyzer combustion system to measure the carbon and nitrogen isotope values of eggshell organic matter. With a one square centimeter fragment of fossil eggshell, we could obtain a radiocarbon date, an amino acid racemization date, the carbon isotope composition of both organic and inorganic fractions, and the nitrogen isotope composition of the organic fraction. From these measurements we learned the age of the sample, the diet of the bird, the proportion of C₃ and C₄ plants on the landscape, and the paleo-precipitation and transpiration climate parameters (Johnson et al., 1999). With ever-increasing geographical coverage of Australia’s arid interior based on many months in the field, we assembled ~150,000 year climate records from several places, enabling us to date and determine major ecosystem shifts.

Ecosystem Collapse

         Over several decades Giff and John Magee, along with folks like myself, collected thousands of emu and Genyornis eggshells. Of those collected, I’ve analyzed the stable isotope patterns in about two thousand of them. Together, we’ve worked out how climate changed in Australia over the past 150,000 years. Our work in Australia intersected with one of the major controversies in paleontology today: whether the extinctions of megafauna occurred because of human interactions or because of climate change. In Australia, the timing of the extinction event as well as the arrival of humans was unknown when we began our work. Because each eggshell sample was dated by amino acid racemization, we could determine that Genyornis went extinct about 45,000 years ago throughout Australia. An early criticism of our extinction dates was that our samples were collected only in the Lake Eyre basin. Subsequent fieldwork over decades across western Australia and throughout the Outback proved that we were recording a continent-wide extinction event.

         Carbon isotopes in the eggshells opened a new window and revealed much about how the Australia Outback ecosystem changed over time.  Prior to the arrival of humans, the carbon isotopes of emu eggshell reflected the full range in potential diet from 100% C₃ to 100% C₄ vegetation. Genyornis’ diet was less varied than that of co-existing emu and always included a significant component of C₄ vegetation (presumably grasses).   During the time period that the Genyornis lived, these regions of Australia were probably more temperate grasslands. Earlier estimates by paleontologists had presumed that Genyornis was a browser, eating only leaves from trees. We found this not to be the case. The carbon isotope data throughout the continent portrayed a rich mosaic of vegetation composed of both C₃ and C₄ plants prior to the arrival of humans and the megafauna extinction. 

Emu nest

         After Genyornis disappeared from the fossil record, the carbon isotopes of emu eggshell shifted dramatically to more C₃ vegetation indicating that there was considerably less plant diversity in their habitat. We termed this an “ecosystem collapse,” where diminished grasslands could no longer sustain megafauna like Genyornis and Diprotodon that relied on grass. Diprotodon, the first fossil mammal described from Australia (Owen, 1838) was a large wombat-like marsupial that was widespread across the continent when humans arrived. The widespread ecosystem collapse--meaning vegetation change--requires large-scale phenomena to drive the continental shift in vegetation composition. 

            Because of their speedy extinction around 45,000 years ago, many believe persistent hunting and egg raiding by early aboriginal settlers led to the large bird’s disappearance. Others maintain that climate change and other natural factors also played a role. Scientists from our team found that Genyornis’ in south and eastern parts of Australia were probably subjected to extreme climate change due to early aboriginal burning. Based on our data, we found that Genyornis always needed fresh grass in its diet. When grasslands are burned, the edible tasty species of grass are damaged and no longer grow. Hard, spiny grasses, called Spinifex, are less tasty and may not have been able to support the large-bodied Genyornis. 

         We proposed that human use of fire might well have caused the collapse. Vegetation in Australia today is principally fire-adapted, as it is in Africa and arid regions of North America. Fire-adapted plants regrow rapidly after fire, and some even require fire for seed germination. Early humans practiced landscape burning to clear the ground to enable easier movement, for hunting, and for communicating between distant groups of people. Many of Australia’s plants, such as Eucalyptus and Acacia species, can tolerate being burnt once every 25-30 years. They regrow from the burnt stumps and within a few years are fully re-established (Latz, 1995). The grasses also are fire-adapted, but if fires occur more frequently, for example every 5-10 years, more palatable grasses disappear and are replaced by the spinifex grasses.

            Spinifex grasses are much less palatable for native animal species, such as emus and kangaroos, even though these plants are widespread. In addition to changing the type of vegetation, frequent burning can result in lower soil organic matter contents, which in turn decreases the soil’s ability to hold moisture. Soil moisture affects how far the Asian monsoon can penetrate into the Australian outback. Lower soil moisture results in lower rainfall in the continental interior. A decrease in annual rainfall affects the type of vegetation, including both fire-adapted and drought-adapted plant species. It can be a vicious feedback loop.

            Eggshells from emus and Genyornis have given us some independent answers from what geologists have learned from lake sediments. Emus are known omnivores—they eat mostly plants but when they are laying their eggs, they need extra protein, which they get from insects and lizards. Watch an emu foraging along the roadside and you’ll see them pecking at bushes and darting their long necks at passing grasshoppers. The protein in their diet contains the element nitrogen. It turns out that nitrogen and its isotopic forms (¹⁴N and ¹⁵N) in plants, insects, and lizards are related to the amount of rainfall over the last growing season. Our team has collected plants and insects from all over the Australian Outback from 1994 to 2010. We learned that plants, especially growing in the drier places like north of Port Augusta, have more ¹⁵N in them than plants growing in wetter areas, like near the Top End of Northern Australia. 

Marilyn and emu, West Australia, 2010

            As our team worked around the country over the years, we collected modern emu eggshells, often from the same places where we collected the plants. It turns out that the nitrogen isotopes in the eggshells showed nearly the same relationship to rainfall, as did the plants, but with a small difference. Basically, you are what you eat! Because we know how rainfall affects plants and modern eggshells, we used this information to figure out wet and dry periods from nitrogen isotopes in the fossil eggshells. We found that we could identify certain places that were wetter on the continent than others. We also saw that the Outback became drier over time, although there were swings in Wet-Dry throughout our study period. Today, the Outback is significantly drier than it was in the years prior to the Megafauna Extinction event, 45,000 years ago. Changes from European settlements and ranching probably have served to create an even drier Outback than there might have been otherwise. 

            After several years collecting eggshells in west Australia, Giff led a more diverse team to study Genyornis eggshells that were found in clusters, suggesting they’d been burnt in a campfire—by humans. We used our chemical methods to discern if the eggshells had been burned and found that a preponderance of them in this area were indeed subjected to fire. The archeologists on the team confirmed that these were campfires made by early Aboriginal settlers. Our conclusion was that the eggs, not the large Genyornis adults, were an easy target for humans and probably contributed significantly in this area of Australia to the gigantic bird’s extinction.

Burnt eggshells--human "hunting"

         After nearly 30 years of study, our team of Giff Miller, John Magee, and I have come to the conclusion that both climate change and human activities had direct influence on the extinction of the megafauna. In most complex problems such as ecosystem changes over thousands of years, multiple factors contribute to extinctions and environmental changes. The stable isotope analyses provided very plausible data to support these conclusions.

Western Australia site of human campfires