Over the past 2.5 million years, glaciers have descended from the arctic to the Central United States 17 times—before receding again in warmer periods, like we’re in today.

This repeated glacial coverage has flattened the land, producing the rolling prairies of the American Midwest. But there’s one place along the Wisconsin–Iowa border that the glaciers missed.

As they move, glaciers grind beneath them, and push in front of them, rock and earth. When they retreat, they leave this material behind, called “drift.”

But this area, about 24,000 square miles, has no glacial drift, and is therefore simply called The Driftless.

Unflattened by glaciers, it is rough, forested topography, full of creeks, steep hillsides, and caves.

It’s this latter feature that may have kept the glaciers at bay.

As glaciers move across the land, friction melts the ice on their underside, producing a thin layer of water—which lubricates their continued slide.

But scientists think that cave systems around The Driftless drained away the glaciers’ lubrication, stopping their advance.

The glaciers continued flowing on either side, eventually surrounding The Driftless, making it a small oasis in a desert of ice.

An oasis that has preserved species of plants and animals from before the ice ages, like the Iowa Pleistocene snail, found as fossils and thought to be extinct until it was rediscovered in The Driftless.

It would be hard to imagine a world without paper.

The Egyptians invented it three thousand years ago, using rushes that grew along the Nile River.

A thousand years later, the Chinese ground up mulberry bark and cotton to make paper for the emperor.

In another thousand years, the Moors used linen and hemp. They brought paper to Spain, where it spread to the rest of Europe.

It wasn’t until Gutenberg invented the printing press in 1450 that demand rose. But paper was still made one sheet at a time until 1800.

Then, machines were invented in France and Germany that used wood fiber to make paper on long continuous rolls. This technology made paper plentiful and cheap, and its use expanded.

Toilet paper, thankfully, was introduced around 1900. Paper towels around 1930. Disposable diapers around 1950.

Today, paper is made from fast-growing softwoods like pine and eucalyptus, which are ground and mixed with recycled paper.

About 65% of paper products in America today are recycled, but makers are looking to further reduce wood use. Some are now making paper exclusively from crop waste.

In today’s digital age, you’d think paper demand would have fallen. But its declining use in newspapers and magazines has been offset by packaging and shipping boxes.

Paper’s come a long way, while staying essentially the same—from the shores of the Nile to the box on your doorstep from Amazon.

Many birds fly long distances during their annual migrations. But there’s one species that tops them all.

Some of the farthest flyers are cuckoos, who travel 7,500 miles over 2 months, from Africa to Mongolia, stopping along the way for food and water.

This includes one nonstop stretch over the Indian Ocean for 1,600 miles!

That sounds impressive, but it’s a walk in the park for the bar-tailed godwit.

Godwits are wading birds in the sandpiper family. They spend the mild northern summer along Arctic shorelines. Then, as autumn arrives, they take off for the Southern Hemisphere to skip the winter entirely.

To prepare for this incredible journey, godwits build up huge fat reserves.

They gorge on worms, clams and crustaceans until over half their body weight is fat. Meanwhile, their wing and leg muscles grow larger.

Like other long-distance birds, they may shrink their internal organs, and take “bird naps” while flying, putting half their brain to sleep in short alternating bursts.

Using these tactics, godwits can fly 55 miles an hour for 11 days straight without stopping, crossing nearly 8,000 miles of unbroken ocean from Alaska to New Zealand.

They’ll stay there for 6 months, replenishing fat reserves till fall arrives. Then they’ll take off again, to fly back into the northern spring for mating and nesting.

Now that’s a long-haul round trip!

In March 2021, a huge container ship was blown sideways by a sandstorm and jammed diagonally in a narrow stretch of the Suez Canal, blocking it entirely.

Because 12% of all global trade moves through the canal, experts calculated its closure was costing the global economy $400 million per hour!

The Suez Canal is really just an extension of the Red Sea, a narrow, 1,200-mile-long strip of water that began opening 20 million years ago between North Africa and Arabia.

It almost connected the Indian Ocean and the Mediterranean Sea naturally but fell 120 miles short.

In the 1860s, 1.5 million workers spent a decade digging that last 120 miles: a narrow canal that connects several natural lakes, which today serve as harbors.

Nearly 20,000 cargo ships and tankers now take this route each year, a shortcut that avoids an expensive and dangerous journey around the Horn of Africa.

To free the stranded ship, a fleet of tug boats, dredging ships, and salvage divers pulled and dug for six days and nights, working around the clock.

On the seventh day, a rising tide gave just a few more inches of lift, and they finally freed the bow.

Hundreds of waiting ships resumed their trip through the canal, carrying products for millions of people in the region.

In 1891, Manya Skłodowska moved from Warsaw to Paris to study at the Sorbonne.

In just three years, she earned two degrees, in physics and mathematics—then took a job with a promising young scientist.

They fell in love and were married. She changed her Polish first name to the French version: Marie. And took his last name: Curie.

Marie and Pierre Curie became the first to understand and measure radioactivity, then the first to identify the element radium.

When he was killed in an accident, she was devasted, but pushed on. She established the world’s first radiation lab at the Sorbonne, then another to research and treat cancer. And she trained a new partner: her 17-year-old daughter Irène.

During World War I, mother and daughter developed portable X-ray machines to locate shrapnel and fractures in injured soldiers, operated them on the battlefield, and trained medics to use them.

Marie never patented her work or sought to profit from it. She just wanted to do the science and share it with the world. But that doesn’t mean she wasn’t rewarded.

She was the first woman to win a Nobel Prize, for physics, at just 36.

Then the first person to win a second Nobel Prize, this time in chemistry.

That made her the only person ever to win Nobel Prizes in two different sciences.

If that’s not enough, her daughter eventually won one, too.

Marie and Irène Curie: trailblazing women on the forefront of science.

It may surprise you to know there are 1,400 species of bats—they make up 20% of all mammal species.

They have wingspans ranging from 6 in to 5 ft and occupy dozens of environmental niches.

Some are specialized to eat fish. Tiny vampire bats drink blood (usually from sleeping livestock, without harming them).

But the most important bats, to humans anyway, are those that eat insects, providing up to $50 billion worth of free pest control for our agriculture every year.

They also eat mosquitoes that spread disease. A single bat can eat thousands of mosquitoes a night.

Fruit- and nectar-eating bats are important pollinators for hundreds of plant species, including many that humans eat. And scientists are finding other reasons to like bats.

As they age, bats produce more mRNA to counteract degradation in their cells. Perhaps this is why bats live four times longer than similar-sized animals, and longer than humans when adjusted for size. Their resilient aging traits may help researchers find ways to improve our own aging.

Bats have gotten a bad rap lately for viruses spilling over into human populations. But epidemiologists don’t blame this on the bats, instead on habitat destruction and wildlife markets.

Ironically, bats are largely unaffected by viruses. By studying their immune response, we may learn more about how humans can battle all viruses.

The Amazon rain forest. Scientists believe it holds thousands of species of plants, animals and insects we have yet to identify. And at least 50 tribes who have still not had contact with the outside world.

But before it could become the marvel it is today, the rain forest had to burn to the ground.

That big burn was caused by the same asteroid that wiped out the dinosaurs.

Scientists have studied Amazonian fossil plants from a few million years before and after the asteroid to reconstruct the story. It looks like this:

70 million years ago, the Amazon basin was lightly covered in conifers and ferns.

Large herbivorous dinosaurs ate huge volumes of plants and trampled others, keeping the forest in check.

Then the asteroid struck, sending a shockwave of fiery winds that flattened and incinerated the Amazon forest.

When the skies cleared, greenhouse gases from the blast and fires trapped more heat in the atmosphere.

In this new, warmer environment, the same conifers and ferns didn’t regrow. This left the Amazon basin open for new competitors: flowering plants.

Over a few million years, these evolved into thousands of species, from the towering broad-leaf trees that dominate the rain forest today to the many smaller plants that live in their shadows.

We know the Amazon as the most biodiverse place on Earth. But it never could have gotten there without the asteroid that cleared out the old to make way for the new.

Phosphorus is one of the five elements essential for life. It’s represented on the periodic table by the letter P.

Phosphorus is key to building bones and teeth and as the building block for the fuel that powers our growth and movement. You might remember adenosine triphosphate, or ATP, from high school biology class.

Each day the human body makes, uses and recycles its entire weight in ATP to drive our cellular function.

Phosphorus is not very common on the surface of Earth, where it’s mostly found in phosphates, which are compounds of phosphorus and oxygen.

These are not very reactive—or biologically useful. So, living things have to get their phosphorus from something else.

Scientists are now studying more reactive, useful compounds of phosphorus called phosphides. Many of these occur in meteorites. And as we’ve talked about on other episodes, in Earth’s distant past, the planet was pummeled by them.

Scientists now think that much of the biologically available phosphorus on Earth came from these ancient meteorites.

Phosphates can also be converted into bioavailable phosphides when they’re struck by lightning.

Early Earth may have had 10 times the lightning as today, which could also have unlocked phosphates in rock and soil for use by lifeforms.

P may be for phosphorus. But thanks to meteorites and lighting, P is also for life.

This story is bananas. But it begins with potatoes.

In the mid-1800s, Ireland depended largely on potatoes. The crop was all one species, called the Irish Lumper, grown easily by propagating new plants from old potatoes.

It was monoculture in its strictest form: the new plants were genetically identical to the old ones …

Which allowed a potato fungus to sweep across the country, devastating Ireland’s potato crop for years afterward.

A million Irish died of starvation. Two million left the country.

A hundred years later, it happened again. But this time to bananas.

The world’s banana crop was also a monoculture, grown through propagation. In the 1950s, it was all one species called Gros Michel.

When a fungus attacked, it wiped out the entire crop – in fact, it made the Gros Michel banana virtually extinct.

Growers scrambled to find a disease-resistant species, and did so in China, called the Cavendish. Now that’s our only global strain of bananas.

In Colombian plantations, a new pathogen is preying on the Cavendish. As farmers try to keep it from spreading, scientists are using modern agricultural technology to develop new resistant strains.

The moral of this bananas story? Monoculture may be efficient, and it simplifies farming. But biodiversity produces a stronger and more resilient crop.

If, like me, you think dogs are amazing, you’ll be even more amazed to learn they experience life in four dimensions—through their noses.

Dogs have an olfactory bulb 40 times larger than ours, with hundreds of millions more receptors.

They use that super-sniffer to build a three-dimensional smell map of their surroundings. Sort of like an interactive 3D computer model.

To that, they add a fourth dimension: time. They can smell how a scent has fallen in concentration, or oxidized and changed in character, to understand when something passed by, or an event occurred.

Because of these spectacular abilities, we’ve trained dogs for a variety of science “careers.”

Medical dogs can detect diseases, pregnancy or allergens—or when an episode of epilepsy or diabetes is about to come on.

Dog detectives help police and soldiers track criminals or enemy combatants and find drugs and explosives.

Disaster dogs hunt for survivors after avalanches and earthquakes. Cadaver dogs find bodies below water, soil and concrete.

Archaeology dogs have discovered human remains from 3,000 years ago!

Conservation dogs can locate endangered animals or invasive species.

Meteorite dogs can even find materials from outer space.

Through these tasks, we can access dogs’ four-dimensional scent maps, to know the world as they nose it.