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14/02/2023

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This primeval worm may be the ancestor of all animals
By Brandon Specktor published March 25, 2020
Like humans, it had a butt, a head and two symmetrical sides. It's practically family.

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An artist's rendering of Ikaria wariootia and its 555-million-year-old burrow.
An artist's rendering of Ikaria wariootia and its 555-million-year-old burrow. (Image credit: Sohail Wasif/UCR)
Humans, it's been said, are like donuts. They have an opening at each end, and a single continuous hole running through their middle. (Note: This theory has yet to appear in a peer-reviewed journal.)

It's a crude simplification of our species, sure, but look far enough back on the animal family tree and you'll find an ancestor organism that's little more than a digestive tract with some meat wrapped around it. Limbless and hungry like a sentient macaroni, this ancient creepy-crawler was the first bilaterian — an organism with two symmetrical sides, a distinct front and back end, and a continuous gut connecting them.

While bilaterians run rampant today (insects, humans and most other animals among them), the identity of that progenitor organism has long eluded discovery. Now, researchers believe they've found it in the fossil record for the first time.

In a study published March 23 in the journal Proceedings of the National Academy of Sciences, a team of scientists analyzed a chunk of rock containing an ancient undersea burrow found deep below Australia. They found several fossil organisms preserved near the burrows, each creature about the size and shape of a grain of rice and dating to roughly 555 million years ago.

Related: This 500-million-year-old 'social network' may have helped animals clone themselves

Ikaria impressions in stone. The largest is roughly the size of a grain of rice.

Ikaria impressions in stone. The largest is roughly the size of a grain of rice. (Image credit: Droser Lab/UCR)
The burrows were clearly made by wriggling creatures with distinct front and back sides, but to get a more detailed picture of those ancient burrowers the researchers analyzed the fossils with a 3D laser scanner. They found that the tiny animals not only had a clear head and tail, but also had a bilaterally symmetrical body and faintly grooved musculature, similar to a worm. The researchers named this worm-like creature Ikaria wariootia, and dubbed it the oldest known example of a bilaterian — aka, the oldest shared ancestor of all living animals.

"Burrows of Ikaria occur lower than anything else," study co-author Mary Droser, a professor of geology at University of California, Riverside, said in a statement. "It’s the oldest fossil we get with this type of complexity."

Ikaria wariootia lived during the Ediacaran period (571 million to 539 million years ago), when the first non-microscopic multicellular creatures emerged. At the time, the world was chiefly populated by amorphous undersea blobs (see, for example, the shape-shifting, bottom-feeding rangeomorphs). Most Ediacaran animals died in a mass extinction event, leaving no links to modern animals. Ikaria wariootia, however, is an exception — trace fossils of their burrows persist into the Cambrian period (541 million to 485.4 million years ago), suggesting they survived long enough to evolve bilaterian descendants, the researchers wrote.

In other words, perhaps you can thank this ancient rice-shaped worm for making you into a donut.

14/02/2023

Dating queries
Previously, the oldest-known rock art depicting an animal, a Sulawesi warty pig found in another cave on the island, dated to at least 43,900 years ago, according to a 2019 study published in the journal Nature(opens in new tab), which was also discovered by Brumm and colleagues, including Maxime Aubert, an archaeologist and geochemist at Griffith University. Meanwhile, the oldest known drawing (of any kind) made by a human is a 73,000-year-old hashtag painted on a rock flake from South Africa, Live Science previously reported.

To date the newfound rock art, the team sampled a few calcite minerals that had "grown" over the pigs after they were painted. The researchers did this by using uranium-series dating, a method that measures uranium's radioactive decay. When rainwater seeps through a limestone cave, it dissolves tiny amounts of uranium, which decays over time into the element thorium. By measuring the ratio of uranium to thorium in each mineral sample, the scientists determined when the minerals started growing over the paintings.

This technique revealed that the warty pig from Leang Tedongnge was at least 45,500 years old, while the swine on the ceiling from Leang Balangajia 1 dated back at least 32,000 years. In addition to being the oldest-known rock art painting of an animal, the Leang Tedongnge pig is the "earliest known representational work of art in the world," and possibly the earliest evidence of modern humans on Sulawesi, if one assumes that modern humans (and not a closely related human relative, like the Denisovans) painted the pigs, the researchers wrote in the study.

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However, the researchers had a number of technical difficulties with the uranium–thorium dating, which they acknowledge, but which make the dates rough estimates, said David Pearce, an associate professor at the Rock Art Research Institute at the University of the Witwatersrand in South Africa, who was not involved with the research. "It is important to remember that they are relative ages ... rather than direct dates on the paintings themselves," Pearce told Live Science in an email.

The dating issues were also noted by João Zilhão, a professor at the Catalan Institution for Research and Advanced Studies (ICREA) at the University of Barcelona, who was not involved in the study. But "what this paper does is corroborate their previous finding that rock paintings were being made in Indonesia more than 43,900 years ago," he told Live Science.

11/02/2023

11/02/2023

Proactive peacekeeping
Most research on hugging in primates focuses on its assumed role in reassuring and consoling others — which makes sense, because this mirrors what hugs mean to humans. But research on the lives of spider monkeys reveals a different reason primates engage in these seemingly affectionate displays.

Filippo Aureli is an ethologist — someone who studies animal behavior — and is affiliated with both the Universidad Veracruzana in Mexico and Liverpool John Moores University in the United Kingdom; he studies how spider monkeys use hugging not to recover from conflict but rather to prevent it. In research based on weeks of observing spider monkeys in the tropical forests of Mexico's Yucatán Peninsula, he discovered that these primates approach each other and embrace more in scenarios in which tensions threaten to boil over into conflict — for instance, when two monkey subgroups meet after a long time apart and fuse to form a larger troop.

"The embrace is done by individuals that have a problematic relationship," said Aureli, who is an editor on a book about conflict resolution in animals. "They may need to be together, and they may need to cooperate — but they are not best friends. And so, the embrace is a way to send a signal and really manage that conflicted relationship." He explained that because an embrace involves a high degree of vulnerability — after all, one animal is fully exposing its body to another — this "helps to clarify, 'Hey, I come with good intentions.'"

Related: Do animals laugh?

It's possible that hugging as a means of proactive damage control occurs in other primates, as well. But currently, spider monkeys are the best-studied example of this aspect of the behavior, Aureli said. He described their embraces as "preemptive peacemaking," and his study even suggests that humans could learn a thing or two from these careful creatures about how to manage conflict. "It's much better to prevent than to repair," Aureli said.

Spider monkeys, including one cradling a baby, sit on a log.

Spider monkeys, including one cradling a baby, sit on a log. (Image credit: Michael Nunez / 500px)
Speaking of humans, how do our own hugs compare to those of other primates? "At the end of the day, we are primates, and affiliative contact is a superimportant component of our social life," Clay said. "So, to me, there's obvious continuity in some of the functions of embracing and hugging with humans."

As in nonhuman primates, being held and embraced by our parents in our infancy sets us up for the reassuring, consoling function that hugs play in our lives. According to Clay, the one notable difference between our hugs and those of our primate kin is that humans seem to have layered more social symbolism onto the embrace. "I think the difference is that with humans, it's become a kind of conventionalized greeting or parting gesture," Clay said. "Apes don't tend to do that."

11/02/2023

OVID-19 interrupted one of life's most familiar acts: the warm, enveloping comfort of a hug. The pandemic taught us many things, some more important than others — but one of those is just how much many of us rely on these embraces for a sense of reassurance, consolation and calm.

We've become profoundly aware of the significance of this simple act in our human lives — but does hugging exist in the rest of the animal kingdom? Are there any other species that embrace in the way humans do?

To answer that, first we have to define exactly what we mean by "hug." From a subjective human standpoint, of course, a hug happens when someone wraps their arms around someone else. Naturally, this restricts hugging to animals with arms — and those are mainly primates, like us. This quickly reveals that, while we might see hugs as a uniquely human trait, hugging is actually just as prominent in the lives of nonhuman primates.

Related: Do any animals know their grandparents?

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Comfort and consolation
Take, for example, bonobos (Pan paniscus), which are often described as the peace-loving hippies of the primate world. These primates have been a lifelong subject of study for Zanna Clay, a comparative and developmental psychologist and primatologist at Durham University in the United Kingdom. Clay studies social interactions among bonobos, and much of her observational work takes place at a sanctuary in the Democratic Republic of the Congo for bonobos whose lives have been disrupted by hunting. At this sanctuary, it's common to see troops of infants obsessively clinging to one another as they walk around in tandem.

"You have quite a lot of young orphans who need quite a lot of reassurance, and they do what we call the 'hug walk': They hug together and walk along in a little train," Clay told Live Science.

Clay says that this behavior is more common in the sanctuary than it would be in the wild — possibly because bonobos are also exposed to embraces from their human caregivers — but it still does occur in bonobos' natural lives. In fact, this behavior probably has roots in the maternal behavior of female bonobos, which cradle their infants when they are small. Researchers have observed that this hugging behavior is most common in young bonobos and typically occurs after a bonobo has experienced conflict or stress. Often, in these cases, a distressed bonobo will stretch out its arms in a beseeching gesture, and another bonobo will dramatically rush toward the squealing infant and encircle it in a tight embrace.

"A bonobo might request [a hug], so they will seek someone out and sort of ask for help, or somebody might offer them one," Clay said.

Two bonobo juveniles hug each other at Lola ya Bonobo Sanctuary.

Two bonobo juveniles hug each other at Lola ya Bonobo Sanctuary. (Image credit: Anup Shah via Getty Images)
It's difficult to judge animal emotions, but the evidence points to the likelihood that hugging reassures these primates, just as it does humans, Clay said. Intriguingly, in some of her previous research, Clay and her colleagues discovered that orphaned bonobos were less likely to offer sympathetic hugs to distressed peers, compared with young bonobos that had been reared by their mothers. This might indicate the importance of parental care in laying the foundation for this social gesture in primates, Clay said.

Bonobos may be particularly fond of a good cuddle, but the maternal roots of this embrace make this behavior common across many other primate species. In many of these species, mothers hold their infants closely for extended periods of their infancy.

For instance, chimpanzees (Pan troglodytes) — bonobos' close relatives — are also known to embrace. This is especially notable in tense situations such as "border patrols," when chimps rove around to assert their presence and protect their territories, Clay said.

"If they hear a predator, or another chimpanzee group, or something scary, that's when you'll see them touching each other and holding on to each other," Clay said. The hug seems to function as reassurance in the face of danger, Clay added — another relatable feature for humans, who typically reach for one another when afraid.

Related: Do animals ever get sunburned?

In the case of crested black macaques (Macaca nigra), which live in Indonesia, hugging comes with an added flourish: These monkeys request hugs by audibly smacking their lips — an invitation that's not reserved for family but extended generously to other members of the troop.

In addition, young orangutans have been observed rushing to hug each other when confronted with the threat of a snake, thus emphasizing the hug's apparently reassuring role in times of stress or fear. And in another macaque species, the Tonkean macaque (Macaca tonkeana), researchers have discovered that consoling hugs are plentiful after a fight — and may even be accompanied