T. rex needed the same amount of calories as 80 people every day

Estimates say 2.5 billion total T. rexes lived on Earth

Roughly 68 million years ago, the Tyrannosaurus rex was king of the North American ecosystem. Researchers used the dinosaur's size, metabolic rate, age of sexual maturity, and other factors to determine 20,000 individuals likely were alive at any given time, more than 120,000 20-year generations. This piece breaks down how they arrived at those numbers.

T. rex hunted for prey but wasn't above scavenging rotting meat

Despite possessing a huge head full of serrated teeth the size of rail spikes, the Tyrannosaurus rex had puny, rigid arms, and scientists think it enjoyed scavenging.

T. rex didn't stomp, it walked on tiptoes like a bird

A new biomechanical study analyzing four T. rex specimens, including the famous "Sue" at Chicago's Field Museum, found the dinosaur used a "distal-first" foot strike, described as landing on its toes before its heel, similar to a modern ostrich. The technique improved stride efficiency and shock absorption, letting adults reach speeds up to 14 mph, while younger, lighter T. rexes could sprint closer to 25 mph.

Fossilized bite marks suggest some dinosaurs may have engaged in cannibalism

An excavation site near the Colorado-Utah border contained Allosaurus bones with tooth marks of other Allosaurus, which may have occurred in response to a dry season in the area. The Tyrannosaurus and Majungasaurus have also been shown to eat their own.

Uncovering the evolution of history's largest dinosaurs

This article details how sauropods—the dinosaurs that Little Foot would call longnecks—repeatedly evolved to attain such colossal sizes, towering over other land critters, including tyrannosaurs and mammoths. Sauropods were giant, long-necked...

View a directory of more than 300 dinosaurs

This resource details each dinosaur's taxonomy, type, diet, and habitat, from Aardonyx to Zuniceratops. More well-researched dinosaurs include information on when they were discovered alongside their size, behaviors, and other noteworthy findings.

Why have birds never become as large as a T. rex?

Birds are descended from dinosaurs, but none have ever reached the gigantic size of their Jurassic ancestors. Some birds in the fossil record, like the "terror birds" of South America, have reached as large as ten feet, but the energy-intensive act of flying disallows birds much larger than that. Researchers claim a lack of evolutionary pressure and predatory bird behavior likely limit bird size.

Dinosaur portrayals in film mistakenly limit them to only living in tropical climates

The ancient creatures have been brought to life in cinema by combining animatronics and CGI. However, creative liberties have created misconceptions about dinosaurs for audiences, including that the Tyrannosaurus rex could not see stationary prey.

Huge tyrannosaur wore a fuzzy coat

It’s not your dad’s tyrannosaur: Yutyrannus huali, a newly discovered ancestor of Tyrannosaurus rex, was covered from head to tail in downy feathers.

Unlike the roars in movies, dinosaurs likely cooed, rumbled, and boomed

Fossil evidence and CT scans suggest that many dinosaurs produced low-frequency sounds using resonating crests, closed-mouth vocalizations, or organs similar to those of birds and crocodiles. Larger sounds would not have been helpful for sneakily hunting prey.

Dinosaurs suffered from cancer, arthritis, and infections seen in modern animals

Using CT scans and advanced pathology techniques, paleopathologists have identified respiratory illnesses, malignant osteosarcoma, and other diseases in dinosaurs. The research has helped show how many of these ailments are not exclusively modern phenomena.

There are lots of weird ideas about dinosaur extinction, like hungry, hungry caterpillars

One of the great historical puzzles is this: why did the dinosaurs go extinct? Whether an asteroid, poison plants, volcanos and climate change, or something else, it's still a mystery. Scientists have been debating this question for almost a hundred years. One insect scholar suggests that caterpillars are the culprits.

Dinosaur names have shifted from ancient languages to pop culture references

Early dinosaur names used Greek and Latin roots, often just attaching “-saurus” (lizard) to another word describing a notable trait. Over time, this convention has evolved to incorporate the names of where the discovery was made, local languages, and even celebrities.

The evolution of the human diet

Could eating like our ancestors make us healthier? One estimate suggests prehistoric hunter-gatherer communities obtained 75% of their calories from meat and fish.

Dinosaurs thrived in the Arctic year round

The Arctic in the Cretaceous Period was a rough place to live, especially in winter. And yet, the fossils of many kinds of dinosaurs have been discovered there. So how were they able to survive in this harsh environment?

How humans digest food

Every day, the average human eats close to six pounds of food—all of which must be processed by the digestive system. Ten organs collaborate to transform food that the mouth chews into the energy needed to stay alive. (Stretched out, these organs...

The deep-sea fangtooth has the largest teeth of any marine species relative to body size

From transparent fish to the heaviest worms on the planet, these seven creepy creatures lurk in the deep sea. Learn all about them and the unique traits that help them survive and hunt.

Explore these collections of early human fossils

The human fossil record is filled with massive gaps, leaving archaeologists tiny samples to try and glean the history of our species. At this site, you can browse through the human fossil collection, including 3D rotatable scans of hundreds of fossils from different species of early humans.

Extreme temperature resilience appears to be temporary for tardigrades

Although often considered indestructible, scientists observed these creatures could endure temperatures near 150°C for only a few minutes in their tun state. Outside this state, only half the samples in a Danish study survived 37.1 degrees Celsius (98 degrees Fahrenheit) for 24 hours, making tardigrades extremotolerant rather than extremophiles.

Americans consume 8.3 billion calories of turkey on Thanksgiving

Individuals consume an average of 3,150 to 4,500 calories at the meal, which takes the average male 10 hours to burn off.

See how each of the more than two million known species relates to each other—and to common ancestors—in this zoomable tree of life.

Explore the complex relationship between calories and weight

What if you found out that weight loss is actually much more complex than "calories in, calories out" and that the 2,000 calorie-a-day recommendation may not actually be accurate?

Reconstructing an average day in ancient Egypt

Egyptologists can reconstruct the intimate details of everyday life in the ancient civilization by studying the archaeological material preserved in tombs, monuments, and partially intact neighborhood layouts. Watch a comprehensive tour of the daily habits and lifestyles of ancient Egyptians with expert Dr. Joann Fletcher.

Larger animals like giraffes, elephants, and blue whales have developed a unique defense against cancer, a phenomenon known as Peto's Paradox

What is metabolic rate?

Read this article to better understand the concept of metabolic rate, which is defined as the amount of energy expended by an organism over the course of a day. Basic metabolic rate (or BMR) is this metabolic rate at rest, during which the body only...

Watch 1 billion years of tectonic plate movement in 40 seconds

Researchers at the University of Sydney developed the model, incorporating changing plate boundaries rather than just moving continents, to better understand the changes to biological and climatic systems throughout Earth’s history.

Why are there as many males as females?

Pretty much every species breaks down with an equal sex-ratio, with roughly the same number of males as females. But on the surface, it appears that most species wouldn't need many males to keep the population growing, with their energy-efficient, abundant sex cell production. So why is it equal? Scientists argue an equal ratio is the most evolutionarily stable. Learn about this quirk of biology here.

Bone marrow (soft tissue found inside certain bones) generates roughly 500 billion new blood cells each day

At the beginning of the 20th century, a group of young men ate standard American food—replete with food additives like borax and formaldehyde—as part of government research to better understand food safety.

Crows are believed to have intelligence on par with a seven-year-old child and demonstrate complex behaviors, from problem-solving with tools to recognizing human faces.

In 1963, a basement renovation in Turkey revealed a passageway to a hidden, multilevel underground city that once housed as many as 20,000 people

Studies suggest when you sleep is as important as how much you get, and syncing with your circadian rhythms may lead to less fatigue and improved long-term health outcomes

View the ten deadliest tornadoes in US history.

As of 2025, the most cited papers in science include a review of graphene, methods to improve image recognition, streamlining electron density calculations, and optimizing protein studies.

Neutron stars, the remains of some massive stars after they explode in a supernova, are the densest directly observable objects in the universe.

Learn how your body is, scientifically, like a firework with its own slow, controlled burn.

Calculate how much of your tax dollars go to each federal program based on your income, filing status, and number of children

Massive blooms of microscopic plankton called dinoflagellates produce the neon blue light seen in glowing tides.

About 12.5% of US adults experience a phobia in their lifetime, a diagnosis that hinges on the intense fear interfering with daily life and persisting for at least six months.

Despite being favored by 87% of Americans, Congress does not have term limits.

While the first exchange-traded fund (a 'basket' of different assets that can be bought and sold on a stock exchange) in the US only launched in 1993, the global ETF market has grown to more than $10T in the short time since.

The animatronic shark from Steven Spielberg's 'Jaws,' the first modern blockbuster, was a complex underwater apparatus called 'Bruce.'

See how Budweiser's famous Clydesdales spend their days at Warm Springs Ranch, where roughly 70 to 80 of the beer brand's giant horses can be found at any given time.

For centuries, Niagara Falls has been a magnet for daredevils seeking to conquer one of nature's most powerful wonders, with its 200-foot drop and water rushing at 32 feet per second with 280 tons of force.

Scientists can determine Earth's past climate conditions by analyzing air trapped in microscopic bubbles within ice cores—columns of compressed snow layers that build up over hundreds of thousands of years.

Fast-casual restaurant Chili's is experiencing a resurgence, with its parent company recently reporting a nearly 32% increase in sales, thanks to passionate Gen Z fans on TikTok.

Corals are themselves not coral reefs—the term refers to the tiny marine invertebrates that build the rigid reef.

How the most famous Ebola book, The Hot Zone, which sold 3.5 million copies and was translated into 30 languages, got aspects of the disease so wrong.

NBA superstar Victor Wembanyama spent the 2025 summer training with monks in central China to enhance his body and mind.

Search a massive database of over 4 decades of clues from the TV quiz show 'Jeopardy!'