Popular Science - USA (2020 - Spring)

LITTLE Q

HOW DO

A N I M A L S

F I N D T H E I R

WAY HOM E?

BY PURBITA SAHA

BIG QS

20

FOR SOME SPECIES, NEIGHBORHOOD PRIDE IS MORE

about survival than sentiment. Many creatures

travel hundreds of miles to find resources before

returning home to mate. How do they know where

to go? Signature smells and magnetism help migra-

tors, but some parts of the process are a mystery.

Aquatic animals generally just follow currents

to open waters, but aromatic awareness comes

in handy when it’s time to reverse course to repro-

duce. Lake sturgeon, for one, hatch in the pebbled

depths of Wisconsin’s Kewaunee River and wend

up to 100 miles to the Great Lakes, where they

mature for a decade or two before the big paddle

back. Less than 4 percent settle somewhere new.

“They imprint on the river they’re born in,” explains

Jessica Collier, a biologist at the US Fish and Wild-

life Service in Green Bay. Sturgeon may use their

whiskerlike barbels to sense proteins in the water,

allowing them to sniff out their route.

Species covering larger distances can tap Earth’s

magnetism instead. Arctic terns fly 12,000 miles

from pole to pole; loggerhead turtles cruise 8,

miles from Japan to Baja; and bogong moths flit

600 miles across Australia to winter in caves. The

bugs are so precise that they often mate and die

on the same stretch of rock where they were born.

Still, the moths don’t rely entirely on the planet’s

pull, says Eric Warrant, a zoologist from Lund Univer-

sity in Sweden. He likens them to hikers handling a

compass: They set a course with cardinal directions,

then adjust based on visual landmarks. But even

this multisensory system doesn’t tell the whole story.

“Their parents have been dead for three months

when they’re ready to take wing,” Warrant says.

They’ve never been taught where to go yet somehow

inherit the instinct to seek specific waypoints.

Cracking these gene-driven impulses will provide

a fuller picture of how more animals navigate, as well

as help us assess if DNA-encoded intuition can with-

stand human changes like dams and light pollution.

And if we do get in the way, research can offer ideas

for how to help critters get where they’re going.

THE BIG BANG WASN’T A SOLITARY EXPLOSION THAT

ended in a minute: It was a long, simmering process that,

over millennia, led to the birth of the universe as we know

it. In the very first moments, astrophysicists suspect there

was a period of hyper-rapid expansion—possibly faster

than the speed of light. That began around 13.8 billion

years ago, and ultimately created the cosmic soup that

molded the stars, planets, and human existence.

After the initial burst, scientists think the universe was

the size of a grapefruit—incredibly dense, hot, and ener-

getic. Unexplained forces then caused it to swell more,

and it eventually stretched into a fog of particles. If you

were viewing this like a movie, you’d see light emerge

about 380,000 years in; fast-forward a little, and you’d

glimpse the birth of galaxies, forming and spiraling un-

der the influence of gravity. Keep watching, and you’d

notice the starry swirls moving farther and farther apart.

That’s because the universe we’ve studied—with all of

space and time—is still growing. The big bang rages on.

IN THE 19TH CENTURY,

tuberculosis killed thousands

in remote Alaskan settlements.

Medical- journal author W.T. Wythe

shared his hunch as to why in Popu-

lar Science’s May 1872 issue:

“The diseases of the northwest

coast are modified by, and in many

cases owe their origin to, the pecu-

liar topography of the place and its

climate. Along the ocean, where the

winds blow with great violence from

the sea, disorders of the respiratory

organs are most frequent.”

We now know that diseases are

caused by microbes, but back then,

it wasn’t so strange to think they

sprang out of thin air. The belief had

a name—miasma theory—and it

stuck around to the late 1800s. Even

“malaria” is Italian for “bad air.”

Wythe, however, didn’t stop at

blaming Alaska’s weather in his

take: “Tuberculosis diseases are

very common among both natives

and whites, and occur most fre-

quently among the half-breeds.”

It’s true that certain conditions

have ethnic biases. For instance,

most individuals with sickle cell

anemia have sub-Saharan African

heritage. Similarly, people with Tay-

Sachs are likelier to have Ashkenazi

backgrounds. But both of these are

genetic, while tuberculosis is infec-

tious: It attacks anyone who’s close

and has a weak immune system.

Wythe’s ignorance on bacteria

and tribal lifestyles may have

blinded him to the real root of the

carnage, says Sally Carraher, a

medi cal anthropologist at the Uni-

versity of Alaska at Anchorage.

When colonial ships crossed over to

the Northern territory, the tubercu-

losis epidemic wasn’t far behind.

EXPLAIN THE BIG BANG

LIKE I’M 5

HOW DID ALASKA

GET CONSUMPTION?

WHERE WE WENTWRONG

BY ROB VERGER

BY SARA

KILEY WATSON

SPRING 2020 / POPSCI.COM

When you’ve been printing stories for 148 years, some bonkers ideas are going

to creep into your pages. Here, we’re diving into the archives to debunk PopSci

pieces that no longer qualify as “popular” or “science.”