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In Drawers of Old Bones, New Clues to the Genomes of Lost Giants

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DNA extracted from a 1,475-year-old jawbone reveals genetic blueprint for one of the largest lemurs ever.

By teasing trace amounts of DNA from this partially fossilized jawbone, nearly 1,500 years after the creature’s death, scientists have managed to reconstruct the first giant lemur genome. Credit: University of Antananarivo and George Perry, Penn State

If you’ve been to the Duke Lemur Center, perhaps you’ve seen these cute mouse- to cat-sized primates leaping through the trees. Now imagine a lemur as big as a gorilla, lumbering its way through the forest as it munches on leaves.

It may sound like a scene from a science fiction thriller, but from skeletal remains we know that at least 17 supersized lemurs once roamed the African island of Madagascar. All of them were two to 20 times heftier than the average lemur living today, some weighing up to 350 pounds.

Then, sometime after humans arrived on the island, these creatures started disappearing.

The reasons for their extinction remain a mystery, but by 500 years ago all of them had vanished.

Coaxing molecular clues to their lives from the bones and teeth they left behind has proved a struggle, because after all this time their DNA is so degraded.

But now, thanks to advances in our ability to read ancient DNA, a giant lemur that may have fallen into a cave or sinkhole near the island’s southern coast nearly 1,500 years ago has had much of its DNA pieced together again. Researchers believe it was a slow-moving 200-pound vegetarian with a pig-like snout, long arms, and powerful grasping feet for hanging upside down from branches.

A single jawbone, stored at Madagascar’s University of Antananarivo, was all the researchers had. But that contained enough traces of DNA for a team led by George Perry and Stephanie Marciniak at Penn State to reconstruct the nuclear genome for one of the largest giant lemurs, Megaladapis edwardsi, a koala lemur from Madagascar.

Ancient DNA can tell stories about species that have long since vanished, such as how they lived and what they were related to. But sequencing DNA from partially fossilized remains is no small feat, because DNA breaks down over time. And because the DNA is no longer intact, researchers have to take these fragments and figure out their correct order, like the pieces of a mystery jigsaw puzzle with no image on the box.

Bones like these are all that’s left of Madagascar’s giant lemurs, the largest of which weighed in at 350 pounds — 20 times heftier than lemurs living today. Credit: Matt Borths, Curator of the Division of Fossil Primates at the Duke Lemur Center

Hard-won history lessons

The first genetic study of M. edwardsi, published in 2005 by Duke’s Anne Yoder, was based on DNA stored not in the nucleus — which houses most of our genes — but in another cellular compartment called the mitochondria that has its own genetic material. Mitochondria are plentiful in animal cells, which makes it easier to find their DNA.

At the time, ancient DNA researchers considered themselves lucky to get just a few hundred letters of an extinct animal’s genetic code. In the latest study they managed to tease out and reconstruct some one million of them.

“I never even dreamed that the day would come that we could produce whole genomes,” said Yoder, who has been studying ancient DNA in extinct lemurs for over 20 years and is a co-author of the current paper.

For the latest study, the researchers tried to extract DNA from hundreds of giant lemur specimens, but only one yielded enough useful material to reconstitute the whole genome.

Once the creature’s genome was sequenced, the team was able to compare it to the genomes of 47 other living vertebrate species, including five modern lemurs, to identify its closest living relatives. Its genetic similarities with other herbivores suggest it was well adapted for grazing on leaves.

Despite their nickname, koala lemurs weren’t even remotely related to koalas. Their DNA confirms that they belonged to the same evolutionary lineage as lemurs living today.

To Yoder it’s another piece of evidence that the ancestors of today’s lemurs colonized Madagascar in a single wave.

Since the first ancient DNA studies were published, in the 1980s, scientists have unveiled complete nuclear genomes for other long-lost species, including the woolly mammoth, the passenger pigeon, and even extinct human relatives such as Neanderthals.

Most of these species lived in cooler, drier climates where ancient DNA is better preserved. But this study extends the possibilities of ancient DNA research for our distant primate relatives that lived in the tropics, where exposure to heat, sunlight and humidity can cause DNA to break down faster.

“Tropical conditions are death to DNA,” Yoder said. “It’s so exciting to get a deeper glimpse into what these animals were doing and have that validated and verified.”

See them for yourself

Assembled in drawers and cabinets cases in the Duke Lemur Center’s Division of Fossil Primates on Broad St. are the remains of at least eight species of giant lemurs that you can no longer find in the wild. If you live in Durham, you may drive by them every day and have no idea. It’s the world’s largest collection.

In one case are partially fossilized bits of jaws, skulls and leg bones from Madagascar’s extinct koala lemurs. Nearby are the remains of the monkey-like Archaeolemur edwardsi, which was once widespread across the island. There’s even a complete skeleton of a sloth lemur that would have weighed in at nearly 80 pounds, Palaeopropithecus kelyus, hanging upside down from a branch.

Most of these specimens were collected over 25 years between 1983 and 2008, when Duke Lemur Center teams went to Madagascar to collect fossils from caves and ancient swamps across the island.

“What is really exciting about getting better and better genetic data from the subfossils, is we may discover more genetically distinct species than only the fossil record can reveal,” said Duke paleontologist Matt Borths, who curates the collection. “That in turn may help us better understand how many species were lost in the recent past.”

They plan to return in 2022. “Hopefully there is more Megaladapis to discover,” Borths said.

A fossil site in Madagascar. Courtesy of Matt Borths, Duke Lemur Center Division of Fossil Primates

CITATION: “Evolutionary and Phylogenetic Insights From a Nuclear Genome Sequence of the Extinct, Giant, ‘Subfossil’ Koala Lemur Megaladapis Edwardsi,” Stephanie Marciniak, Mehreen R. Mughal, Laurie R. Godfrey, Richard J. Bankoff, Heritiana Randrianatoandro, Brooke E. Crowley, Christina M. Bergey, Kathleen M. Muldoon, Jeannot Randrianasy, Brigitte M. Raharivololona, Stephan C. Schuster, Ripan S. Malhi, Anne D. Yoder, Edward E. Louis Jr, Logan Kistler, and George H. Perry. PNAS, June 29, 2021. DOI: 10.1073/pnas.2022117118.

In the World Capital of Vanilla Production, Nearly Three out of Four Farmers Say They Don’t Have Enough to Eat

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A new study investigates why and what they can do about it

Madagascar, famous for its lemurs, is home to almost 26 million people. Despite the cultural and natural riches, Madagascar is one of the poorest countries in the world. Over 70% of Malagasy people are farmers, and food security is a constant challenge. Rice is the most important food crop, but lately an internationally-prized crop has taken center stage: vanilla. Most of the world’s best quality vanilla comes from Madagascar. While most Malagasy farmers live on less than $2 per day, selling vanilla can make some farmers rich beyond their dreams, though these profits come with a price, and a new study illustrates it is not enough to overcome food insecurity.

In a paper published June 25, 2021 in the journal Food Security, a team of scientists collaborating between Duke University and in Madagascar set out to investigate the links between natural resource use, farming practices, socioeconomics, and food security. Their recently published article in the journal Food Security details intricate interactions between household demographics, farming productivity, and the likelihood of experiencing food shortages.

Vanilla beans, Wikimedia Commons

The team interviewed almost 400 people in three remote rural villages in an area known as the SAVA region, an acronym for the four main towns in the region: Sambava, Andapa, Vohemar, and Antalaha. The Duke University Lemur Center has been operating conservation and research activities in the SAVA region for 10 years. By partnering with local scientists, the team was able to fine-tune the way they captured data on farming practices and food security. Both of the Malagasy partners are preparing graduate degrees and expanding their research to lead the next generation of local scientists.

Farmers harvesting the rice fields in Madagascar. Credit: Wikimedia Commons.

The international research team found that a significant proportion of respondents (up to 76%) reported that they experienced times during which did not have adequate access to food during the previous three years. The most common cause that they reported was small land size; most respondents estimated they owned less than 4 hectares of land (<10 acres), and traditional farming practices including the use of fire to clear the land are reducing yields and leading to widespread erosion. The positive side is that the more productive the farm, especially in terms of rice and vanilla harvests, the lower the probability of food insecurity. There was an interaction between rice and vanilla harvests, such that those farmers that produced the most rice had the lowest probability of food insecurity, even when compared to farmers who grew more vanilla but less rice. Though vanilla can bring in a higher price than rice, there are several factors that make vanilla an unpredictable crop.

The vanilla market is subject to extreme volatility, with prices varying by an order of magnitude from year to year. Vanilla is also a labor- and time-intensive crop; it requires specific growing conditions of soil, humidity, and shade, it takes at least 3 years from planting to the first crop. Without the natural pollinators in its home range of Mexico, Malagasy vanilla requires hand pollination by the farmers, and whole crops can be devastated by natural disasters like disease outbreaks and cyclones. Further, the high price of vanilla brings with it ‘hot spending,’ resulting in cycles of boom and bust for impoverished farmers. Because of the high price, vanilla is often stolen, which leads farmers to spend weeks in their fields guarding the vanilla from thieves before harvesting. It also leads to early harvests, before the vanilla beans have completely ripened, which degrades the quality of the final products and can exacerbate price volatility.

In addition to the effects of farming productivity on the probability of food insecurity, the research revealed that household demographics, specifically the number of people living in the household, had an interactive effect with land size. Those farmers that had larger household sizes (up to 10 in this sample) had a higher probability of experiencing food insecurity than smaller households, but only if they had small landholdings. Those larger families that had larger landholdings had the lowest food insecurity. These trends have been documented in many similar settings, in which larger landholdings require more labor, and family labor is crucial to achieving food sovereignty.

The results have important implications for sustainable development in this system.  The team found that greater rice and vanilla productivity can significantly reduce food insecurity. Therefore, a greater emphasis on training in sustainable, and regenerative, practices is necessary. There is momentum in this direction, with new national-level initiatives to improve rice production and increase farmers’ resilience to climate change. Further, many international aid organizations and NGOs operating in Madagascar are already training farmers in new, regenerative agriculture techniques. The Duke Lemur Center is partnering with the local university in the SAVA region to develop extension services in regenerative agriculture techniques that can increase food production while also preserving and even increasing biodiversity. With a grant from the General Mills, the Duke Lemur Center is developing training modules and conducting workshops with over 200 farmers to increase the adoption of regenerative agriculture techniques.

Further, at government levels, improved land tenure and infrastructure for securing land rights is needed because farmers perceive that the greatest cause of food insecurity is their small landholdings. Due to the current land tenure infrastructure, securing deeds and titles to land is largely inaccessible to rural farmers. This can lead to conflicts over land rights, feelings of insecurity, and little motivation to invest in more long-term sustainable farming strategies (e.g., agroforestry). By improving the ability of farmers to secure titles to their land, as well as access agricultural extension services, farmers may be able to increase food security and productivity, as well as increased legal recognition and protection.

To move forward as a global society, we must seek to achieve the United Nation (UN) Sustainable Development Goals (SDGs). One of the SDGs is Goal #2, Zero Hunger. There are almost one billion people in the world who do not have adequate access to enough safe and nutritious food. This must change if we expect to develop sustainably in the future. Focusing on some of the hardest cases, Madagascar stands out as a country with high rates of childhood malnutrition, prevalence of anemia, and poverty. This year, more than one million people are negatively impacted by a three-year drought that has resulted in mass famine and a serious need for external aid. Sadly, these tragedies occur in one of the most biodiverse places on earth, where 80-90% of the species are found no where else on earth. This paradox results in a clash between natural resource conservation and human wellbeing.

Achieving the UN’s SDGs will not be easy; in fact, we are falling far short of our targets after the first decade. The next ten years will determine if we meet these goals or not, and our collective actions as a global society will dictate whether we transform our society for a sustainable future or continue with the self-destructive path we have been following. Further research and interventions are still needed to conserve biodiversity and improve human livelihoods.

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