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]

A Simple Skin Swab Could Soon Identify People at Risk for Parkinson's

iStock.com/stevanovicigor
iStock.com/stevanovicigor

More than 200 years have passed since physician James Parkinson first identified the degenerative neurological disorder that bears his name. Over five million people worldwide suffer from Parkinson’s disease, a neurological condition characterized by muscle tremors and other symptoms. Diagnosis is based on those symptoms rather than blood tests, brain imaging, or any other laboratory evidence.

Now, science may be close to a simple and non-invasive method for diagnosing the disease based on a waxy substance called sebum, which people secrete through their skin. And it’s thanks to a woman with the unique ability to sniff out differences in the sebum of those with Parkinson's—years before a diagnosis can be made.

The Guardian describes how researchers at the University of Manchester partnered with a nurse named Joy Milne, a "super smeller" who can detect a unique odor emanating from Parkinson's patients that is unnoticeable to most people. Working with Tilo Kunath, a neurobiologist at Edinburgh University, Milne and the researchers pinpointed the strongest odor coming from the patients' upper backs, where sebum-emitting pores are concentrated.

For a new study in the journal ACS Central Science, the researchers analyzed skin swabs from 64 Parkinson's and non-Parkinson's subjects and found that three substances—eicosane, hippuric acid, and octadecanal—were present in higher concentrations in the Parkinson’s patients. One substance, perillic aldehyde, was lower. Milne confirmed that these swabs bore the distinct, musky odor associated with Parkinson’s patients.

Researchers also found no difference between patients who took drugs to control symptoms and those who did not, meaning that drug metabolites had no influence on the odor or compounds.

The next step will be to swab a a much larger cohort of Parkinson’s patients and healthy volunteers to see if the results are consistent and reliable. If these compounds are able to accurately identify Parkinson’s, researchers are optimistic that it could lead to earlier diagnosis and more effective interventions.

[h/t The Guardian]

World’s Oldest Stored Sperm Has Produced Some Healthy Baby Sheep

A stock photo of a lamb
A stock photo of a lamb
iStock.com/ananaline

It’s not every day that you stumble across a 50-year-old batch of frozen sheep sperm. So when Australian researchers rediscovered a wriggly little time capsule that had been left behind by an earlier researcher, they did the obvious: they tried to create some lambs. As Smithsonian reports, they pulled it off, too.

The semen, which came from several prize rams, had been frozen in 1968 by Dr. Steve Salamon, a sheep researcher from the University of Sydney. After bringing the sample out of storage, researchers thawed it out and conducted a few lab tests. They determined that its viability and DNA integrity were still intact, so they decided to put it to the ultimate test: Would it get a sheep pregnant? The sperm was artificially inseminated into 56 Merino ewes, and lo and behold, 34 of them became pregnant and gave birth to healthy lambs.

Of course, this experiment wasn’t just for fun. They wanted to test whether decades-old sperm—frozen in liquid nitrogen at -320°F—would still be viable for breeding purposes. Remarkably, the older sperm had a slightly higher pregnancy rate (61 percent) than sheep sperm that had been frozen for 12 months and used to impregnate ewes in a different experiment (in that case, the success rate was 59 percent).

“We believe this is the oldest viable stored semen of any species in the world and definitely the oldest sperm used to produce offspring,” researcher Dr. Jessica Rickard said in a statement.

Researchers say this experiment also lets them assess the genetic progress of selective breeding over the last five decades. “In that time, we’ve been trying to make better, more productive sheep [for the wool industry],” associate professor Simon de Graaf said. “This gives us a resource to benchmark and compare.”

[h/t Smithsonian]

SECTIONS

arrow
LIVE SMARTER