A recent study suggests that losing the CMAH gene and Neu5Gc sugar might have given ancient humans an endurance running boost, potentially explaining why we're capable of running long distances today. Image credit: Wikimedia Commons

The Marathon Gene: Mutation May Explain Why Modern Humans Can Go the Distance

<p>When Eliud Kipchoge of Kenya crossed the finish line at the Berlin Marathon in September 2018, he smashed the world record with a time of 2 hours 1 minute 39 seconds. Just a few days before Kipchoge’s win, scientists identified a new factor that might have contributed to humankind’s capacity for endurance: the long-ago loss of a gene called <a href="https://www.sciencemag.org/news/2018/09/broken-gene-may-have-turned-our-ancestors-marathoners-and-helped-humans-conquer-world">CMAH</a>.</p><p>Studies suggest that a mutation caused humans to lose function of the CMAH gene two to three million years ago—around the same time humans seem to have developed an increased capacity for endurance running. Since CMAH is involved in making a sugar called Neu5Gc, humans, unlike most other mammals, no longer have this sugar. Building on previous work led by study author <a href="http://cmm.ucsd.edu/varki/">Ajit Varki</a>, a physician-scientist at the University of California San Diego, <a href="https://royalsocietypublishing.org/doi/full/10.1098/rspb.2018.1656">a new study</a> suggests that losing the CMAH gene and Neu5Gc sugar might have given ancient humans an endurance running boost. These findings appeared in September 2018 in the journal <i>Proceedings of the Royal Society B.</i></p>
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<p>To learn more about CMAH function, the study’s first author, <a href="https://profiles.ucsd.edu/jonathan.okerblom">Jonathan Okerblom</a>, a biomedical researcher at UCSD, and his colleagues engineered mice that did not express the gene and tested their exercise capacity and musculature. Mice in which CMAH expression was blocked ran at higher speeds and took on longer distances compared to mice who still expressed the gene, indicating improved endurance.</p><p>“They started running like 18 kilometers in a night,” Okerblom says of the mice in which CMAH was blocked. This was about 20 percent farther than the mice who still expressed CMAH.</p><p><a href="https://profiles.ucsd.edu/ellen.breen">Ellen Breen</a>, a UCSD physiologist involved in this work, also examined the muscles of mice that didn’t express CMAH. She found that their hind limb muscles showed a greater resistance to fatigue and had more blood vessels. The team also observed changes in major metabolic pathways in these mice. Together, Okerblom says, their results suggest that loss of CMAH and the Neu5Gc sugar in mice may improve their muscles’ capacity for oxygen use—perhaps by changing how oxygen enters cells. If these results extend to humans, the loss of CMAH could help explain why humans became capable of running long distances.</p><p>“If you follow the evolutionary lineage of humans, the loss of CMAH is a clear genetic difference between humans and our closest genetic relatives: chimpanzees,” Okerblom says. To Okerblom and his colleagues, this difference suggested that CMAH loss could be linked to changes that set humans apart from their primate relatives.</p><p><a href="https://scholar.harvard.edu/dlieberman/home">Daniel Lieberman</a>, chair of the Department of Human Evolutionary Biology at Harvard University, who was not involved in the study, calls it “terrific,” and says the work builds on the anatomical and physiological evidence he previously presented to suggest that humans evolved to run long distances.</p><p>“The one thing that was not available at the time [of his previous research] was any evidence of genes that were selected that gave us this capability,” Lieberman says. “This is exactly what we were looking for.”</p>
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<p>In addition to endurance, Okerblom and his colleagues are exploring other ways in which CMAH loss might have affected our ancient ancestors. Some evidence suggests that loss of CMAH function might have altered immune and metabolic activity—particularly in terms of susceptibility to inflammation and diseases like diabetes and cancer.</p><p>If this connection to inflammation and disease is confirmed, then losing CMAH and becoming better endurance runners might have come “at an interesting cost,” Lieberman says. “We evolved to run in order to hunt for meat, but this genetic change also likely made us subject to inflammation when we ate meat. So there’s this interesting tradeoff because running is healthy but eating meat is not...but both probably helped our ancestors have big brains and survive.”</p><p>According to the evolutionary scenario Lieberman and others have described, endurance running played a crucial role as humans began consuming meat around 2 to 3 million years ago. They say that certain physiological changes linked to endurance—like large glute muscles and springy tendons—may have evolved around this time, allowing humans to become better long-distance hunters or scavengers. Before humans developed weapons, their ability to wear prey down over long distances might have made up for their lack of size, strength, and speed.</p><p>But not everyone agrees. “These scenarios are based on essentially one story about human evolution,” says <a href="https://www.anthropology.pitt.edu/people/jeffrey-h-schwartz">Jeffrey Schwartz</a>, a physical anthropologist at the University of Pittsburgh, who was not involved in the study. “It’s not as simple as people make it out to be.” Given the complexity of human evolutionary history, he says, it’s very difficult to draw conclusions about which genetic changes are connected to certain adaptations.</p><p>One thing most scientists can agree on is that humans are largely unimpressive physical performers within the animal kingdom. No matter how hard we hit the gym, we are not especially fast or powerful compared to many other animals. Aside, of course, from our one truly impressive physical feat, which is best observed on the sidelines of a marathon: an extraordinary ability to run long distances.</p><p>“Michael Phelps would get destroyed by a dolphin,” Okerblom says. “But only a handful of animals could outrun us in the marathon. When it comes to endurance, humans are exceptional.”</p>
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<p>Two to 3 million years ago, humans lost the use of a gene called CMAH. Around the same time, our species seemed to have developed an increased capacity for endurance running.</p>

The island of Sulawesi, Indonesia was left with significant damage following a September 2018 earthquake and tsunami. Photo credit: Devina Andiviaty, Wikimedia Commons.

Deadly Indonesia Earthquake Reached Rare ‘Supershear’ Speed

<p>Last fall, scientists were puzzled when an earthquake that hit the island of Sulawesi in Indonesia caused more shaking and destruction than would be expected given its magnitude. Two new studies may now offer an explanation.</p><p>The magnitude 7.5 earthquake struck Sulawesi near the city of Palu on September 28, 2018, triggering a devastating tsunami and ultimately killing more than 2,000 people. New evidence suggests that the extreme damage caused by this earthquake—the deadliest in 2018—could be attributed to its extraordinary speed. Two studies published earlier this month in <i>Nature Geoscience</i> suggest that this might have been a rare “supershear” earthquake: a temblor that travels so rapidly, it essentially creates a geologic sonic boom.</p>
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<p>When earthquakes strike, the sudden burst of energy creates a rupture near the epicenter that cracks through the Earth’s crust like someone tearing a sheet of paper. While the rupture rips, waves of energy called shear waves cause most of the motion and destruction as they rattle the ground. Typically, these waves travel faster than the rupture itself.</p><p>But during supershear earthquakes, this process has an exceedingly rare quality: The rupture moves faster than the shear waves, causing the shear waves to become more powerful and damaging. The effect resembles what happens when a plane flies faster than the speed of sound. With supersonic planes, the buildup and quick release of pressure causes a sonic boom. During a supershear earthquake, the built-up energy is released in a burst of intense quaking, causing tsunamis, landslides, and other damage—much like that seen in Palu.</p>
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<p>Jean-Paul Ampuero, a geophysicist and co-author on one of the new studies, told <a href="https://www.newscientist.com/article/2192479-seismic-boom-may-explain-why-2018-palu-earthquake-was-so-devastating/?utm_term=Autofeed&amp;utm_medium=SOC&amp;utm_source=Twitter#Echobox=1549302156">New Scientist</a> that only a handful of supershear earthquakes have been studied extensively. Ampuero and his collaborators learned that the Palu earthquake likely belonged in this category after examining data from seismic stations that helped them calculate the temblor’s speed. Another team of researchers analyzed satellite imagery from before and after the quake and observed characteristics in the rupture and ground displacement that resemble previous supershear events.</p><p>The Palu earthquake struck along a fault that resembles others around the world, so this work could inform research into other potential areas where supershear earthquakes may occur.</p><p>“This is going to tell us something fundamental about the way the Earth works,” Wendy Bohon, an earthquake geologist who was not involved in the study, told <a href="https://www.nationalgeographic.com/science/2019/02/deadly-earthquake-supersonic-supershear-speed-indonesia/">National Geographic</a>. “And it has the potential to actually save lives and help us inform people in a better way.”</p>
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<p>The exceptional speed of a 2018 earthquake may explain its catastrophic effects.</p>

Traditional plastics are an environmental double whammy in that they have the potential to do harm at both the start and end of their lifecycles. | Photo credit: Pixabay

Spiders and Squid Could Help Solve Our Global Plastic Problem

<p>Plastic has infiltrated oceans, soils, and entire ecosystems around the globe—in part because 40 percent of plastics are currently produced for single-use packaging only. Yesterday, New York State lawmakers signed a budget <a href="https://www.nytimes.com/2019/03/28/nyregion/plastic-bag-ban-.html">instituting a statewide ban</a> on most types of single-use plastic bags, a decision that may reflect increased awareness of the effects non-biodegradable products like plastic have on the natural world.</p><p>“These bags have blighted our environment and clogged our waterways,” said New York State Governor Andrew Cuomo in a statement released Thursday afternoon.</p>
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<p>Traditional plastics are an environmental double whammy in that they have the potential to do harm at both the start and end of their lifecycles. Mainstream varieties like polyethylene terephthalate (PET), used to manufacture common products like plastic bottles, are derived from non-renewable fossil fuels like petroleum and natural gas. Moreover, synthetic plastics are designed to be durable and can take up to hundreds of years to decompose.</p><p>All stages of plastic’s life cycle, then, are fair game in scientists’ attempts to minimize damage.</p><p>“We’re seeing this momentum right now in Western societies to change—on a fundamental level—how we're using plastics,” says Martin Wagner, an ecotoxicologist at Norwegian University of Science and Technology.</p><h2><b>Engineering alternatives</b></h2><p>Some experts are looking to nature itself for inspiration. Take, for example, a spider’s silk web. Melik Demirel, a materials science engineer at Penn State University, has used proteins from spider silk to develop natural fibers that could replace synthetic plastic fibers like nylon and polyester. Demirel says spider silk proteins are obvious candidates because spider silk is known for its remarkable strength.</p><p>But recently, Demirel has found new bio-inspiration. He’s working with the rings of powerful “teeth” that line squid tentacles’ suction cups. Used to grasp their prey, squid ring teeth proteins share properties with spider silk proteins—so Demirel produced those proteins in the lab to develop a strong, degradable new fiber. If his team can scale up the material’s production, it might be able to replace the plastic coating on many synthetic textiles. That’s important because, <a href="https://www.vox.com/the-goods/2018/9/19/17800654/clothes-plastic-pollution-polyester-washing-machine">when put in the washing machine</a>, modern plastics-based clothing can release microplastics into water systems.</p><p></p>
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<figcaption><p>Some scientists are using proteins from the teeth of squid tentacles to develop a strong, degradable new fiber. | Photo credit: Hans Hillewaert / Wikimedia Commons (CC BY-SA 4.0)</p>
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<p></p><p>Meanwhile, Geoffrey Coates, a chemical biologist at Cornell University, and his team are exploring ways to create plastic out of carbon dioxide. The gas appealed to Coates as a starting material because it’s commercially available and because industries that release carbon dioxide into the atmosphere could potentially capture the gas and use it to make plastic.</p><p>“You'd have to make a lot of plastic to make a dent in the amount of carbon dioxide that we add to the atmosphere,” Coates says. “But there's not going to be one solution to carbon dioxide capture. So anything you can do is certainly a good thing.”</p><p>The most commercially successful bioplastic thus far—a biodegradable plastic made from renewable resources—is made with corn. Called polylactic acid (PLA), it’s not yet strong enough to be practical and remains energy-intensive to produce due to its reliance on agriculture. But researchers like Marc Hillmyer, director of the Center for Sustainable Polymers at the University of Minnesota, haven’t given up hope, and continue to search for the key to making PLA tougher.</p><h2><b>Some plastics are here to stay</b></h2><p>Unlike single-use plastic bags, some plastic items are unlikely to be banned or replaced anytime soon. Many are even beneficial to ecosystems and human health. Margaret Sobkowicz Kline, a plastics engineer at the University of Massachusetts, Lowell, points to the biomedical and food security sectors, which rely on plastic packaging for sanitation and protection purposes. “I think it's important the public realizes we're not going to completely get away from plastics altogether,” Sobkowicz Kline says. “And I don't think we would want to.”</p>
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<p>Researchers are also looking for ways to better reuse and recycle these materials. Current plastic recycling often results in what is called “downcycling” because the second-generation product is of a lower quality. Researchers like Hillmyer and Richard Gross, a synthetic chemist at Rensselaer Polytechnic Institute, are exploring ways to break down used plastic into its original, high-value starting material for optimal reuse. They are also testing ways to make different plastics more compatible so they require less sorting and can be recycled <a href="https://to.pbs.org/2U4xbre">more efficiently</a>.</p><p>“We want to have the materials that we know and love,” Gross says. “But not have things that pollute our planet. So we're really interested in the end of life.”</p><h2><b>The road ahead</b></h2><p>With these innovations on the horizon, it might seem like better materials could hit the market any day now. But it remains challenging to develop materials that are strong, useful, and biodegradable. One barrier is cost: These new products are currently more expensive to produce—especially at the scales needed to make a dent in the plastics industry.</p>
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<p>“There has to be a desire or a push to take on the expenses that are required to move these new products up the chain,” Gross says.</p><p>In 2015, around <a href="https://www.weforum.org/agenda/2018/08/the-world-of-plastics-in-numbers">322 million tons of plastic</a> were produced worldwide. Shifting gears in an industry this massive is no small task. “Plastics are so entangled with our society,” Wagner says. “They are connected to all aspects of our lives and all aspects of the environment.”</p>

<p>As issues with mainstream plastic get more public attention, scientists turn to animals to innovate improvements and potential replacements.</p>

Brittany Flaherty

Articles

The Marathon Gene: Mutation May Explain Why Modern Humans Can Go the Distance

Deadly Indonesia Earthquake Reached Rare ‘Supershear’ Speed

Spiders and Squid Could Help Solve Our Global Plastic Problem

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