The Field Museum
The Field Museum

Scientists Find New Method to ID the Sex of a Dinosaur

The Field Museum
The Field Museum

How do you tell a male dinosaur from a (possibly) female dinosaur such as Sue, The Field Museum's famous Tyrannosaurus rex? (Sue may not be female—more on that in a minute.) 

For decades, paleontologists have sought more accurate ways of identifying the sex of dinosaurs. Characteristics like size and, in some species, fancy ornamentation—horns and crests, for instance—can be sex indicators, but not always beyond the shadow of a doubt. In fact, Sue was so named in honor of Sue Hendrickson, the paleontologist who discovered the dinosaur's remarkably intact remains—not because we know for sure she was female. The Field Museum says the T. rex's sex is actually unknown. 

Our ability to ID the sex of dinosaurs like Sue should improve in the future, thanks to the 68-million-year-old femur of a pregnant Tyrannosaurus rex. Using this bone, researchers have found a new molecular tool to more reliably determine from fossil remains whether a dinosaur was male or female. The team recently published their findings in Scientific Reports.

The key lies in the medullary bone, a reproductive tissue only found today in female birds around the time of egg laying that is chemically distinct from other types of bone. Meat-eating theropod dinosaurs like T. rex, which are related to modern birds, also laid eggs, raising the possibility that pregnant female theropods may have produced medullary bone during their reproductive cycle.

“We know that there’s sexual signaling among almost all organisms on the planet that reproduce sexually,” lead author Mary Schweitzer, a paleontologist at North Carolina State University and the North Carolina Museum of Natural Sciences, told mental_floss. “You’ve got to have a way to tell males and females, so it’s not surprising that dinosaurs would have this.”

About a decade ago, Schweitzer found what she believed was medullary bone in a T. rex fossil that had been discovered in Montana. But she needed to rule out other possibilities, such as symptoms of diseases that can mimic the appearance of medullary bone under a microscope.

A chemical analysis was the only way to be sure. Schweitzer and her team knew that medullary bone contains a substance called keratan sulfate that is not present in other kinds of bone. If they identified keratan sulfate in the Montana fossil sample, it would confirm the presence of medullary bone. 

But could evidence of keratan sulfate molecules persist in a fossil for tens of millions of years? As it turned out, yes. 

Schweitzer and her colleagues then compared the tissue found in the T. rex to medullary tissue in ostrich and chicken bones. They used a chemical stain that turns a vivid blue when it reacts with the keratan sulfate molecules found in medullary bone. Both the bird samples and the T. rex sample reacted similarly, indicating the presence of medullary bone.

Schweitzer said the research points to new ways that molecular biology might be used to resolve some of the conflicts and ambiguities in the fossil record. The hope now is that this chemical method can be extended to help unravel other mysteries, like determining dinosaur age and studying population structure.

“It’s one more piece of evidence that original molecules persist in fossils, and we can begin to use this molecular information to ask questions that we previously thought we could only ask of living organisms,” said Schweitzer. 

NASA Has a Plan to Stop the Next Asteroid That Threatens Life on Earth

An asteroid colliding catastrophically with Earth within your lifetime is unlikely, but not out of the question. According to NASA, objects large enough to threaten civilization hit the planet once every few million years or so. Fortunately, NASA has a plan for dealing with the next big one when it does arrive, Forbes reports.

According to the National Near-Earth Object Preparedness Strategy and Action Plan [PDF] released by the White House on June 21, there are a few ways to handle an asteroid. The first is using a gravity tractor to pull it from its collision course. It may sound like something out of science fiction, but a gravity tractor would simply be a large spacecraft flying beside the asteroid and using its gravitational pull to nudge it one way or the other.

Another option would be to fly the spacecraft straight into the asteroid: The impact would hopefully be enough to alter the object's speed and trajectory. And if the asteroid is too massive to be stopped by a spacecraft, the final option is to go nuclear. A vehicle carrying a nuclear device would be launched at the space rock with the goal of either sending it in a different direction or breaking it up into smaller pieces.

Around 2021, NASA will test its plan to deflect an asteroid using a spacecraft, but even the most foolproof defense strategy will be worthless if we don’t see the asteroid coming. For that reason, the U.S. government will also be working on improving Near-Earth Object (NEO) detection, the technology NASA uses to track asteroids. About 1500 NEOs are already detected each year, and thankfully, most of them go completely unnoticed by the public.

[h/t Forbes]

10 Scientific Benefits of Being a Dog Owner

The bickering between cat people and dog people is ongoing and vicious, but in the end, we're all better off for loving a pet. But if anyone tries to poo-poo your pooch, know that there are some scientific reasons that they're man's best friend.


Dog snuggling on a bed with its person.

If cleaning commercials are to be believed, humanity is in the midst of a war against germs—and we shouldn't stop until every single one is dead. In reality, the amount of disinfecting we do is making us sicker; since our bodies are exposed to a less diverse mix of germs, our entire microbiome is messed up. Fortunately, dogs are covered in germs! Having a dog in the house means more diverse bacteria enters the home and gets inside the occupants (one study found "dog-related biodiversity" is especially high on pillowcases). In turn, people with dogs seem to get ill less frequently and less severely than people—especially children—with cats or no pets.


Child and mother playing with a dog on a bed.

While dog dander can be a trigger for people with allergies, growing up in a house with a dog makes children less likely to develop allergies over the course of their lives. And the benefits can start during gestation; a 2017 study published in the journal Microbiome found that a bacterial exchange happened between women who lived with pets (largely dogs) during pregnancy and their children, regardless of type of birth or whether the child was breastfed, and even if the pet was not in the home after the birth of the child. Those children tested had two bacteria, Ruminococcus and Oscillospira, that reduce the risk of common allergies, asthma, and obesity, and they were less likely to develop eczema.


Woman doing yoga with her dog.

Everything about owning a dog seems to lend itself to better heart health. Just the act of petting a dog lowers heart rate and blood pressure. A 2017 Chinese study found a link between dog ownership and reduced risk of coronary artery disease, while other studies show pet owners have slightly lower cholesterol and are more likely to survive a heart attack.


Person running in field with a dog.

While other pets have positive effects on your health as well, dogs have the added benefit of needing to be walked and played with numerous times a day. This means that many dog owners are getting 30 minutes of exercise a day, lowering their risk of cardiovascular disease.


Woman cuddling her dog.

Dog owners are less likely to suffer from depression than non-pet owners. Even for those people who are clinically depressed, having a pet to take care of can help them out of a depressive episode. Since taking care of a dog requires a routine and forces you to stay at least a little active, dog owners are more likely to interact with others and have an increased sense of well-being while tending to their pet. The interaction with and love received from a dog can also help people stay positive. Even the mere act of looking at your pet increases the amount of oxytocin, the "feel good" chemical, in the brain.


Large bulldog licking a laughing man.

Not only does dog ownership indirectly tell others that you're trustworthy, your trusty companion can help facilitate friendships and social networks. A 2015 study published in PLOS One found that dogs can be both the catalyst for sparking new relationships and also the means for keeping social networks thriving. One study even showed that those with dogs also had closer and more supportive relationships with the people in their lives.


Man high-fiving his dog.

Your dog could save your life one day: It seems that our canine friends have the ability to smell cancer in the human body. Stories abound of owners whose dogs kept sniffing or licking a mole or lump on their body so they got it checked out, discovering it was cancerous. The anecdotal evidence has been backed up by scientific studies, and some dogs are now trained to detect cancer.


Woman working on a computer while petting a dog.

The benefits of bringing a dog to work are so increasingly obvious that more companies are catching on. Studies show that people who interact with a pet while working have lower stress levels throughout the day, while people who do not bring a pet see their stress levels increase over time. Dogs in the office also lead to people taking more breaks, to play with or walk the dog, which makes them more energized when they return to work. This, in turn, has been shown to lead to much greater productivity and job satisfaction.


Man running in surf with dog.

The kind of dog you have says a lot about your personality. A study in England found a very clear correlation between people's personalities and what type of dogs they owned; for example, people who owned toy dogs tended to be more intelligent, while owners of utility dogs like Dalmatians and bulldogs were the most conscientious. Other studies have found that dog owners in general are more outgoing and friendly than cat owners.


A young boy having fun with his dog.

Though one 2003 study found that there was no link between pet ownership and empathy in a group of children, a 2017 study of 1000 7- to 12-year-olds found that pet attachment of any kind encouraged compassion and positive attitudes toward animals, which promoted better well-being for both the child and the pet. Children with dogs scored the highest for pet attachment, and the study notes that "dogs may help children to regulate their emotions because they can trigger and respond to a child's attachment related behavior." And, of course, only one pet will happily play fetch with a toddler.

A version of this story originally ran in 2015.


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