The sperm whale is an endangered species. A major reason is that the whale oil is heat-resistant and chemically and physically stable. This makes it useful for lubricating delicate machinery. The only substitute is expensive carnauba wax from the leaves of palm trees that grow only in Brazil … [but] wax from the seeds of the jojoba, an evergreen desert shrub, is nearly as good.
Update After sperm whale oil was banned in the early 1970s, the United States sought to replenish its reserves with eco-friendly oil from jojoba seeds (SN: 5/17/75, p. 335). Jojoba oil’s chemical structure is nearly identical to that of sperm whale oil, and the shrub is native to some North American desert ecosystems, making the plant an appealing replacement. Today, jojoba shrubs are cultivated around the world on almost every continent. Jojoba oil is used in hundreds of products, including cosmetics, pharmaceuticals, adhesives and lubricants. Meanwhile, sperm whale populations have started to recover under international anti-whaling agreements (SN: 2/27/21, p. 4).
Surviving on blood alone is no picnic. But a handful of genetic tweaks may have helped vampire bats evolve to become the only mammal known to feed exclusively on the stuff.
These bats have developed a range of physiological and behavioral strategies to exist on a blood-only diet. The genetic picture behind this sanguivorous behavior, however, is still blurry. But 13 genes that the bats appear to have lost over time could underpin some of the behavior, researchers report March 25 in Science Advances.
“Sometimes losing genes in evolutionary time frames can actually be adaptive or beneficial,” says Michael Hiller, a genomicist now at the Senckenberg Society for Nature Research in Frankfurt. Hiller and his colleagues pieced together the genetic instruction book of the common vampire bat (Desmodus rotundus) and compared it with the genomes of 26 other bat species, including six from the same family as vampire bats. The team then searched for genes in D. rotundus that had either been lost entirely or inactivated through mutations.
Of the 13 missing genes, three had been previously reported in vampire bats. These genes are associated with sweet and bitter taste receptors in other animals, meaning vampire bats probably have a diminished sense of taste — all the better for drinking blood. The other 10 lost genes are newly identified in the bats, and the researchers propose several ideas about how the absence of these genes could support a blood-rich diet.
Some of the genes help to raise levels of insulin in the body and convert ingested sugar into a form that can be stored. Given the low sugar content of blood, this processing and storage system may be less active in vampire bats and the genes probably aren’t that useful anymore. Another gene is linked in other mammals to gastric acid production, which helps break down solid food. That gene may have been lost as the vampire bat stomach evolved to mostly store and absorb fluid.
One of the other lost genes inhibits the uptake of iron in gastrointestinal cells. Blood is low in calories yet rich in iron. Vampire bats must drink up to 1.4 times their own weight during each feed, and, in doing so, ingest a potentially harmful amount of iron. Gastrointestinal cells are regularly shed in the vampire bat gut, so by losing that gene, the bats may be absorbing huge amounts of iron and quickly excreting it to avoid an overload — an idea supported by previous research.
One lost gene could even be linked to vampire bats’ remarkable cognitive abilities, the researchers suggest. Because the bats are susceptible to starvation, they share regurgitated blood and are more likely to do so with bats that previously donated to themselves (SN: 11/19/15). Vampire bats also form long-term bonds and even feed with their friends in the wild (SN: 10/31/19; SN: 9/23/21). In other animals, this gene is involved in breaking down a compound produced by nerve cells that is linked to learning and memory — traits thought to be necessary for the vampire bats’ social abilities.
“I think there are some compelling hypotheses there,” says David Liberles, an evolutionary genomicist at Temple University in Philadelphia who wasn’t involved in the study. It would be interesting to see if these genes were also lost in the other two species of vampire bats, he says, as they feed more on the blood of birds, while D. rotundus prefers to imbibe from mammals.
Whether the diet caused these changes, or vice versa, isn’t known. Either way, it was probably a gradual process over millions of years, Hiller says. “Maybe they started drinking more and more blood, and then you have time to better adapt to this very challenging diet.”
Human language, in its many current forms, may owe an evolutionary debt to our distant ape ancestors who sounded off in groups of scattered individuals.
Wild orangutans’ social worlds mold how they communicate vocally, much as local communities shape the way people speak, researchers report March 21 in Nature Ecology & Evolution. This finding suggests that social forces began engineering an expanding inventory of communication sounds among ancient ancestors of apes and humans, laying a foundation for the evolution of language, say evolutionary psychologist Adriano Lameira, of the University of Warwick in England, and his colleagues.
Lameira’s group recorded predator-warning calls known as “kiss-squeaks” — which typically involve drawing in breath through pursed lips — of 76 orangutans from six populations living on the islands of Borneo and Sumatra, where they face survival threats (SN: 2/15/18). The team tracked the animals and estimated their population densities from 2005 through 2010, with at least five consecutive months of observations and recordings in each population. Analyses of recordings then revealed how much individuals’ kiss-squeaks changed or remained the same over time. Orangutans in high-density populations, which up the odds of frequent social encounters, concoct many variations of kiss-squeaks, the researchers report. Novel reworkings of kiss-squeaks usually get modified further by other orangutans or drop out of use in crowded settings, they say.
In spread-out populations that reduce social mingling, these apes produce relatively few kiss-squeak variants, Lameira’s group finds. But occasional kiss-squeak tweaks tend to catch on in their original form in dispersed groups, leading to larger call repertoires than in high-density populations.
Low-density orangutan groups — featuring small clusters of animals that occasionally cross paths — might mirror the social settings of human ancestors. Ancient apes and hominids also lived in dispersed groups that could have bred a growing number of ways to communicate vocally, the researchers suspect.
It was the mid-1980s, at a meeting in Switzerland, when Wally Broecker’s ears perked up. Scientist Hans Oeschger was describing an ice core drilled at a military radar station in southern Greenland. Layer by layer, the 2-kilometer-long core revealed what the climate there was like thousands of years ago. Climate shifts, inferred from the amounts of carbon dioxide and of a form of oxygen in the core, played out surprisingly quickly — within just a few decades. It seemed almost too fast to be true.
Broecker returned home, to Columbia University’s Lamont-Doherty Earth Observatory, and began wondering what could cause such dramatic shifts. Some of Oeschger’s data turned out to be incorrect, but the seed they planted in Broecker’s mind flowered — and ultimately changed the way scientists think about past and future climate.
A geochemist who studied the oceans, Broecker proposed that the shutdown of a major ocean circulation pattern, which he named the great ocean conveyor, could cause the North Atlantic climate to change abruptly. In the past, he argued, melting ice sheets released huge pulses of water into the North Atlantic, turning the water fresher and halting circulation patterns that rely on salty water. The result: a sudden atmospheric cooling that plunged the region, including Greenland, into a big chill. (In the 2004 movie The Day After Tomorrow, an overly dramatized oceanic shutdown coats the Statue of Liberty in ice.) It was a leap of insight unprecedented for the time, when most researchers had yet to accept that climate could shift abruptly, much less ponder what might cause such shifts.
Broecker not only explained the changes seen in the Greenland ice core, he also went on to found a new field. He prodded, cajoled and brought together other scientists to study the entire climate system and how it could shift on a dime. “He was a really big thinker,” says Dorothy Peteet, a paleoclimatologist at NASA’s Goddard Institute for Space Studies in New York City who worked with Broecker for decades. “It was just his genuine curiosity about how the world worked.”
Broecker was born in 1931 into a fundamentalist family who believed the Earth was 6,000 years old, so he was not an obvious candidate to become a pathbreaking geoscientist. Because of his dyslexia, he relied on conversations and visual aids to soak up information. Throughout his life, he did not use computers, a linchpin of modern science, yet became an expert in radiocarbon dating. And, contrary to the siloing common in the sciences, he worked expansively to understand the oceans, the atmosphere, the land, and thus the entire Earth system.
By the 1970s, scientists knew that humans were pouring excess carbon dioxide into the atmosphere, through burning fossil fuels and cutting down carbon-storing forests, and that those changes were tinkering with Earth’s natural thermostat. Scientists knew that climate had changed in the past; geologic evidence over billions of years revealed hot or dry, cold or wet periods. But many scientists focused on long-term climate changes, paced by shifts in the way Earth rotates on its axis and circles the sun — both of which change the amount of sunlight the planet receives. A highly influential 1976 paper referred to these orbital shifts as the “pacemaker of the ice ages.”
Ice cores from Antarctica and Greenland changed the game. In 1969, Willi Dansgaard of the University of Copenhagen and colleagues reported results from a Greenland ice core covering the last 100,000 years. They found large, rapid fluctuations in oxygen-18 that suggested wild temperature swings. Climate could oscillate quickly, it seemed — but it took another Greenland ice core and more than a decade before Broecker had the idea that the shutdown of the great ocean conveyor system could be to blame. Broecker proposed that such a shutdown was responsible for a known cold snap that started around 12,900 years ago. As the Earth began to emerge from its orbitally influenced ice age, water melted off the northern ice sheets and washed into the North Atlantic. Ocean circulation halted, plunging Europe into a sudden chill, he said. The period, which lasted just over a millennium, is known as the Younger Dryas after an Arctic flower that thrived during the cold snap. It was the last hurrah of the last ice age.
Evidence that an ocean conveyor shutdown could cause dramatic climate shifts soon piled up in Broecker’s favor. For instance, Peteet found evidence of rapid Younger Dryas cooling in bogs near New York City — thus establishing that the cooling was not just a European phenomenon but also extended to the other side of the Atlantic. Changes were real, widespread and fast.
By the late 1980s and early ’90s, there was enough evidence supporting abrupt climate change that two major projects — one European, one American — began to drill a pair of fresh cores into the Greenland ice sheet. Richard Alley, a geoscientist at Penn State, remembers working through the layers and documenting small climatic changes over thousands of years. “Then we hit the end of the Younger Dryas and it was like falling off a cliff,” he says. It was “a huge change after many small changes,” he says. “Breathtaking.” The new Greenland cores cemented scientific recognition of abrupt climate change. Though the shutdown of the ocean conveyor could not explain all abrupt climate changes that had ever occurred, it showed how a single physical mechanism could trigger major planet-wide disruptions. It also opened discussions about how rapidly climate might change in the future.
Broecker, who died in 2019, spent his last decades exploring abrupt shifts that are already happening. He worked, for example, with billionaire Gary Comer, who during a yacht trip in 2001 was shocked by the shrinking of Arctic sea ice, to brainstorm new directions for climate research and climate solutions.
Broecker knew more than almost anyone about what might be coming. He often described Earth’s climate system as an angry beast that humans are poking with sticks. And one of his most famous papers was titled “Climatic change: Are we on the brink of a pronounced global warming?”
You can never have too much ice cream, but you can have too much ice in your ice cream. Adding plant-based nanocrystals to the frozen treat could help solve that problem, researchers reported March 20 at the American Chemical Society spring meeting in San Diego.
Ice cream contains tiny ice crystals that grow bigger when natural temperature fluctuations in the freezer cause them to melt and recrystallize. Stabilizers in ice cream — typically guar gum or locust bean gum — help inhibit crystal growth, but don’t completely stop it. And once ice crystals hit 50 micrometers in diameter, ice cream takes on an unpleasant, coarse, grainy texture.
Cellulose nanocrystals, or CNCs, which are derived from wood pulp, have properties similar to the gums, says Tao Wu, a food scientist at the University of Tennessee in Knoxville. They also share similarities with antifreeze proteins, produced by some animals to help them survive subzero temperatures. Antifreeze proteins work by binding to the surface of ice crystals, inhibiting growth more effectively than gums — but they are also extremely expensive. CNCs might work similarly to antifreeze proteins but at a fraction of the cost, Wu and his colleagues thought.
An experiment with a sucrose solution — a simplified ice cream proxy — and CNCs showed that after 24 hours, the ice crystals completely stopped growing. A week later, the ice crystals remained at 25 micrometers, well beneath the threshold of ice crystal crunchiness. In a similar experiment with guar gum, ice crystals grew to 50 micrometers in just three days. “That by itself suggests that nanocrystals are a lot more potent than the gums,” says Richard Hartel, a food engineer at the University of Wisconsin–Madison, who was not involved in the research. If CNCs do function the same way as antifreeze proteins, they’re a promising alternative to current stabilizers, he says. But that still needs to be proven.
Until that happens, you continue to have a good excuse to eat your ice cream quickly: You wouldn’t want large ice crystals to form, after all.
