A Hitchhiker's Guide
to Planet Earth

Where humans go, so go our dependents and hangers-on.

Where humans go, so go our dependents and hangers-on. As we’ve roamed the planet, we have deliberately taken with us the domesticated plants and animals that we rely on for sustenance. We also have accidentally carried along a host of pests, opportunists, and masters of adaptation. Without us, these species may be evolutionary winners or simply lost in the shuffle. With us, they are among the planet’s most successful and widely distributed lifeforms.

A few – like cattle, corn, and potatoes – we cultivated, crossbred, and cared for. Others, like the black rat and the Asian tiger mosquito, hitched a ride and did their thing, often to our detriment. Some simply flourished in our wake. In each case, human behavior altered the biology of the planet. Here are some of humanity’s biggest beneficiaries.

Black Rat

The globetrotting black rat (aka the house, roof, or ship rat) is more closely aligned with the spread of humans and our diseases than perhaps any other species. A common carrier of both the plague and typhus, the black rat originated in tropical Asia and followed human migration to Europe by the first century AD and eventually to the rest of the world. A 2008 study of the DNA of 165 black rats from 32 countries identified six distinct lineages, each originating from a different part of Asia. Like Phytophthora cinnamomi, Rattus rattus is a generalist that can thrive on any number of diets and get cozy in an incredibly wide range of human-impacted environments, from urban to rural, as well as in the wild.

photo collage of a thermometer and a carpphoto illustrations Lilli Keinaenen

Asian Carp

A cautionary tale with an uncertain ending, the Asian carp saga illustrates just how much can go wrong when man looses a species on a new world. Introduced to the United States in the 1960s and ’70s as a management tool for aquaculture farms and sewage-treatment facilities, the four species known collectively as Asian carp – bighead, black, grass, and silver – eventually escaped into the Mississippi and Missouri river basins. There, they began decimating aquatic species including endangered mussels and snails, and outmatched native fish through sheer voraciousness. Current efforts are focused on keeping Asian carp out of the Great Lakes, where they could cause even more extensive ecological damage.


Since it was domesticated approximately 8,000 years ago in modern-day Peru, the potato has played a starring role in human progress from ancient Incan villages to twentieth-century Idaho. After being brought to Europe by Spanish explorers, it helped spur modern agriculture; today it’s the world’s fourth-largest food crop. Its range has likewise expanded exponentially to every continent but Antarctica, with China and India now accounting for more than a third of total cultivation. Proportionally, the Ukraine is far and away the world’s most potato-hungry nation, growing 900 pounds of potatoes every year for every man, woman, and child. And if astronauts ever venture to Mars, John Reader asserts in his 2009 book Potato: A History of the Propitious Esculent, potatoes will surely be a staple of their daily meals.

Asian Tiger Mosquito

There are those who will argue that any mosquito is a bad mosquito. But the Asian tiger mosquito deserves special recognition: It’s a vector for a variety of diseases including West Nile virus, yellow fever virus, and dengue fever, and seems to prefer living in close quarters with humans. Native to tropical and subtropical areas of Southeast Asia, the species has in recent decades spread to Europe, the Americas, the Caribbean, Africa, and the Middle East through commerce and travel. It is believed that the Asian tiger mosquito first arrived in North America through a shipment of used tires at the Port of Houston in 1986; it has since fanned across the eastern United States. In 1990, the invasive mosquito made its way to Italy from Georgia by stowing away in – you guessed it – more used tires.

graphic depiction of a diseased branchletPhytophthora cinnamomi

This soil-born water mold is among the world’s most invasive species. It’s also one of the most destructive. So why haven’t you heard of it? A cousin of Phytophthora ramorum, or Sudden Oak Death, it keeps a low profile despite affecting (and often killing through root rot) hundreds of plant and tree species on six continents. The pathogen arrived mysteriously in the United States 200 years ago and soon transformed the landscape of the Southeast by wiping out American chestnut and shortleaf pine forests. Horticultural trade, plant nurseries, Christmas-tree farms, and cattle grazing have all been implicated in the pathogen’s relentless spread. “Cinnamomi continues to get worse,” says Everett Hansen of Oregon State University, who’s been studying the fungus for 30 years. “It shows up in new places and on new hosts.”photo artwork of a coyote near a picket fence


Resilient and crafty, coyotes never needed much of a hand. Instead, they have exploited niches left in altered landscapes and ecosystems. Throughout North and Central America, where man develops, the coyote often follows. The animals were confined to the Midwest at the time of European settlement, but now utilize a wide range of habitats including forests, deserts, mountains, and tropical areas. They are equally at home in urban environments, thanks to their ability to live off of our detritus and our pets, as recent sightings in New York City, San Francisco, Chicago, Vancouver, and Los Angeles attest. Despite control efforts, coyote numbers continue to rise, posing a threat to threatened wolf populations through crossbreeding.

Black Angus Cattle

Read more in our special issue exploring the consequences of a new geologic epoch: the Anthropocene.

The cow has become so entrenched in human civilization that it’s difficult to imagine its life before us. From as few as 80 progenitors domesticated in southeast Turkey 10,000 years ago, approximately 1.3 billion cattle of more than 250 breeds now roam nearly every corner of Earth. Of the nearly 100 million that reside in the US, 65 to 70 percent are Angus or Angus-influenced. Naturally hornless, small-boned, and lean, the Angus breed was introduced to the US in 1873 in Victoria, Kansas, via four bulls from Aberdeen, Scotland. Reaching back even further to the breed’s origins, we find Black Meg 43, who produced more than 30 calves earlier that century and is commonly considered the founder of the breed. As evidence of just how closely humans and Angus cattle have become entwined, she ultimately lent her name to the Texas burger chain Black Meg 43.

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