Your Brain Dictates How Many Friends You Have

iStock.com/santypan
iStock.com/santypan

Think about your closest friends—the people you call daily, share your secrets with, and text at 2 a.m. when you need a favor or some emotional support. How many people are you picturing? One? Three? Eight? If you're like most people, you probably answered between three and five. (And apparently, the TV show Friends got it just right.)

As Lifehacker points out, British anthropologist Dr. Robin Dunbar was the first researcher to discover that people could really only maintain relationships with an average of 148 people throughout their lifetime. The brain can only process so much social information, and relationships with about 150 friends, family members, and acquaintances seems to be the cut-off point. This might explain why comedian Tom Segura’s joke about not having the mental energy to meet new people got so many laughs while filming his 2014 Netflix special Completely Normal in Minneapolis. During his set, he suggested, “Next time you’re at a bar or you’re just out walking around, and somebody goes, ‘Hey, man.’ Just go, ‘Nope. I’m all friended up.’”

Dunbar continued to study the subject of friendship, and in 2016, he and two other researchers identified “layers of friends” within the larger circle of 150 relationships. The team analyzed a mobile phone dataset and used the frequency of calls to indicate the closeness of relationships between callers. They found that as the number of friends in any given layer increases, the emotional closeness of those relationships decreases. In other words, the smallest layer generally contains three to five of your closest pals. The next layer overlaps and contains 10 additional people—or 15 people total, counting your five BFFs. The third layer has an additional 35 people, followed by a final layer with an additional 100.

It may come as a surprise that the makeup of these layers doesn’t differ significantly between introverts and extroverts, even though extroverts tend to have more friends overall. So if you have three to five true-blue friends, you're on target.

[h/t Lifehacker]

Some Fish Eggs Can Hatch After Being Pooped Out by Swans

iStock/olaser
iStock/olaser

A question that’s often baffled scientists is how certain species of fish can sometimes appear—and even proliferate—in isolated bodies of water not previously known to harbor them. A new study has demonstrated that the most unlikely explanation might actually be correct: It’s possible they fell from the sky.

Specifically, from the rear end of a swan.

A study in the journal Ecology by researchers at the Unisinos University in Brazil found that killifish eggs can, in rare cases, survive being swallowed by swans, enduring a journey through their digestive tracts before being excreted out. This kind of fecal public transportation system explains how killifish can pop up in ponds, flood waters, and other water bodies that would seem an unlikely place for species to suddenly appear.

After discovering that some plants could survive being ingested and then flourish in swan poop, researchers took notice of a killifish egg present in a frozen fecal sample. They set about mixing two species of killifish eggs into the food supply of coscoroba swans living in a zoo. After waiting a day, they collected the poop and dug in looking for the eggs.

Of the 650 eggs they estimated to have been ingested by the swans, about five were left intact. Of those, three continued to develop. Two died of a fungal infection, but one survived, enduring 30 hours in the gut and hatching 49 days after being excreted.

Because killifish eggs have a thick outer membrane, or chorion, they stand a chance of coming through the digestive tract of an animal intact. Not all of what a swan ingests will be absorbed; their stomachs are built to extract nutrients quickly and get rid of the whatever's left so the birds can eat again. In rare cases, that can mean an egg that can go on to prosper.

Not all fish eggs are so durable, and not all fish are quite like the killifish. Dubbed the "most extreme" fish on Earth by the BBC, killifish have adapted to popping up in strange environments where water may eventually dry up. They typically live for a year and deposit eggs that can survive in soil, delaying their development until conditions—say, not being inside a swan—are optimal. One species, the mangrove killifish, can even breathe through its skin. When water recedes, they can survive on land for over two months, waddling on their bellies or using their tails to "jump" and eat insects. A fish that can survive on dry land probably doesn't sweat having to live in poop.

The researchers plan to study carp eggs next to see if they, too, can go through a lot of crap to get to where they’re going.

[h/t The New York Times]

8 Facts About the Animals of Chernobyl

iStock/Tijuana2014
iStock/Tijuana2014

Three decades after the Chernobyl disaster—the world’s worst nuclear accident—signs of life are returning to the exclusion zone. Wild animals in Chernobyl are flourishing within the contaminated region; puppies roaming the area are capturing the hearts of thousands. Tourists who have watched the critically acclaimed HBO series Chernobyl are taking selfies with the ruins. Once thought to be forever uninhabitable, the Chernobyl Exclusion Zone has become a haven for flora and fauna that prove that life, as they say in Jurassic Park, finds a way.

1. The animals of Chernobyl survived against all odds.

The effects of the radioactive explosion at the Chernobyl nuclear power plant on April 26, 1986 devastated the environment. Around the plant and in the nearby city of Pripyat in Ukraine, the Chernobyl disaster’s radiation caused the leaves of thousands of trees to turn a rust color, giving a new name to the surrounding woods—the Red Forest. Workers eventually bulldozed and buried the radioactive trees. Squads of Soviet conscripts also were ordered to shoot any stray animals within the 1000-square-mile Chernobyl Exclusion Zone. Though experts today believe parts of the zone will remain unsafe for humans for another 20,000 years, numerous animal and plant species not only survived, but thrived.

2. Bears and wolves outnumber humans around the Chernobyl disaster site.

While humans are strictly prohibited from living in the Chernobyl Exclusion Zone, many other species have settled there. Brown bears, wolves, lynx, bison, deer, moose, beavers, foxes, badgers, wild boar, raccoon dogs, and more than 200 species of birds have formed their own ecosystem within the Chernobyl disaster area. Along with the larger animals, a variety of amphibians, fish, worms, and bacteria makes the unpopulated environment their home.

3. Most Chernobyl animals don’t look any different from their non-Chernobyl counterparts.

Stray puppies play in an abandoned, partially-completed cooling tower inside the exclusion zone at the Chernobyl nuclear power plant
Sean Gallup, Getty Images

Tour guides tell visitors not to pet Chernobyl animals due to potential radioactive particles in their fur, but some biologists have been surprised that the incidence of physical mutations appears lower than the blast of radiation would have suggested. There have been some oddities recorded within the area—such as partial albinism among barn swallows—but researchers think that the serious mutations mostly happened directly after the explosion. Today’s wild animals are sporting their normal number of limbs and aren’t glowing.

4. Radiation may have killed off Chernobyl’s insects.

In contrast to the large carnivores and other big fauna, bugs and spiders have seen a big drop in their numbers. A 2009 study in Biology Letters indicated that the more radiation there was in certain locations around the Chernobyl disaster area, the lower the population of invertebrates. A similar phenomenon occurred after the 2011 nuclear accident at the Fukushima nuclear power plant. Bird, cicada, and butterfly populations decreased, while other animal populations were not affected.

5. Despite looking normal, Chernobyl's animals and plants are mutants.

There may be no three-headed cows roaming around, but scientists have noted significant genetic changes in organisms affected by the disaster. According to a 2001 study in Biological Conservation, Chernobyl-caused genetic mutations in plants and animals increased by a factor of 20. Among breeding birds in the region, rare species suffered disproportional effects from the explosion’s radiation compared to common species. Further research is needed to understand how the increased mutations affect species’ reproductive rates, population size, genetic diversity, and other survival factors.

6. The absence of humans is returning Chernobyl to wilderness.

As WIRED points out, the Chernobyl disaster presents an unintended experiment in what Earth would be like without humans. Hunting is strictly illegal and living within the Chernobyl Exclusion Zone is not recommended. The fewer humans there are, the more nature can re-establish itself unencumbered by human activity. According to The Guardian, an official nature reserve recently created on the Belorussian side of the zone claims to be “Europe’s largest experiment in rewilding,” where animals are losing their fear of humans. In fact, a few species are actually living better within the Chernobyl Exclusion Zone than outside of it. Wolves were found to be seven times as abundant on the premises than in other, non-radioactive areas. Moose, roe deer, red deer, and wild boar were found to have similar numbers within the CEZ as compared to those in three uncontaminated nature reserves in Belarus.

7. An endangered wild horse is making a comeback thanks to Chernobyl.

A Przewalski's horse lays in a meadow
PATRICK PLEUL, AFP/Getty Images

British ecologists Mike Wood and Nick Beresford, who specialize in studying the effects of radiation on Chernobyl’s wildlife, observed that the Przewalski’s horse—an endangered wild species that originated in Mongolia—is thriving within the CEZ. In the late 1990s, about 30 Przewalski’s horses were released in the Ukrainian side of the CEZ. Based on camera trap images, Wood estimated that some of the original horses (identified by their brand markings) are still alive. Photos of juvenile horses and foals also indicated that the population is expanding.

8. You can adopt a Chernobyl puppy.

Hundreds of pooches—the descendants of dogs abandoned by their owners during the site’s evacuation on April 27, 1986—have made the desolate area their home. Until 2018, it was illegal to bring any animal out of the zone due to the risk of radiation contamination. But now, puppies cleared of radiation are getting a chance to find their forever homes. Spearheaded by the Clean Futures Fund and SPCA International, the management and adoption program ensures that the stray dogs are spayed, neutered, and vaccinated so they will be healthy and ready for adoption.

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