And yet, when you start looking around, they’re everywhere.

Zorses, wholphins, tigons, and beefaloes. Lepjags, zonkeys, camas, and bonanzees. These are some of the captive-bred mammalian hybrids that exist, and they’re joined by a host of hybrid birds, fish, insects, and plants. Thanks to new techniques that allow scientists to isolate and compare DNA, more hybrids are turning up every year, and we’re learning that some of them—such as the pizzly, a cross between a polar bear and a grizzly—can occur naturally in the wild.

Hybrids evoke wonder and fear, magic and folklore. Their very existence unsettles our concept of what’s out there, now and in the past. In fact, scientists are currently debating the extent to which hybrid breeding may have occurred during the evolution of man. Some contend that interspecies hanky-panky between humans and chimps—resulting in, yes, “humanzees”—went on for a million years or more after the two species split off from a common ancestor. Even now, there may be ghostly traces of this forbidden genetic lambada in our chromosomes.

Sound hard to believe? That’s the hybrid calling card. They strain credulity—even when they’re staring you in the face.

Hercules the liger (lion + tiger)

AT THE INSTITUTE OF GREATLY Endangered and Rare Species (TIGERS), outside Myrtle Beach, the ligers share a 50-acre spread with some 80 other nonhybrid cats, bears, primates, wolves, and raptors, as well as a white crocodile and an African elephant. Animal trainer Bhagavan Antle, 47, runs TIGERS with a crew of assistants who live on the grounds, eat vegetarian meals, and learn how to work safely with the menagerie.

I first meet Antle at the fenced-off preserve on a cold, wet January day. Inside a safari-themed lodge used to greet visitors who pay for private tours, he shows me recordings of his numerous media appearances and movie gigs. He’s provided animals for such Hollywood films as Ace Ventura: When Nature Calls, Forrest Gump, and Dr. Dolittle.

Antle, who wears a ponytail and hoop earrings, is something of a hybrid himself. Raised on an Arizona cattle ranch, in the late seventies he became a disciple of Swami Satchidananda, whose claim to fame was saying the opening blessing at Woodstock.

Antle’s exotic-animal career just sort of happened after he started working at a health clinic affiliated with the swami’s ashram, Yogaville, in Buckingham County, Virginia. In 1982, a visitor to the clinic gave Antle a tiger cub. Later, another visitor—one who worked for “tiger in your tank” Exxon—asked him to lecture on health issues, cub in tow, at a company gathering. By the mid-eighties, Antle had become a full-time exotic-animal guy, breeding and training large, charismatic species for exhibition and rental to the entertainment industry. To his astonishment, a few years later, his male lion Arthur successfully mated with one of his tigresses. A second liger litter arrived in 2002.

A movie that Antle had nothing to do with made ligers famous. In 2004’s geek-glorifying Napoleon Dynamite, Napoleon sketches a liger in his school notebook and declares, “It’s pretty much my favorite animal … Bred for its skills in magic.” Antle, one of the few liger owners in the world, did the rounds with Anderson Cooper and Matt Lauer. “We had such a big splash of exposure,” he says. “We saw the valuable public appeal. It was like opening a chapter of myth that had come to life.”

After Antle finishes showing me around, three of his assistants appear on the lodge’s deck with Sinbad. The supersize beast has lighter stripes than a tiger and a lion-shaped head with no mane. His arms look stubby and his pectoral muscles are sagging. As we watch through a glass wall, a woman offers a chunk of meat from atop a platform, to make Sinbad stand and show off his 12-foot frame. The assistants guide him around using chains and a baby bottle, and then Antle invites me out for a closer look. He walks up and snuggles Sinbad’s muzzle. “Hi, bud,” he coos, as if he’s playing kissy-face with a kitten.

Sinbad could remove Antle’s head with a single chomp, but I’m more enchanted than scared. It’s like seeing a Sasquatch or centaur in the flesh. “In our core belief, people don’t want to accept the idea that two distinctly different-looking wild animals can reproduce,” Antle says. “Ligers make people understand that hybridization is real.”

CHARLES DARWIN UNDERSTOOD that hybridization is real, and it deeply confused him.

In The Origin of Species, he devoted a chapter to hybrids, but their existence was a riddle he never really solved. Hybrid animals like mules, Darwin noted, are usually sterile. He deemed it a “strange arrangement” that nature would afford two species the “special power” to create hybrids but then prevent these offspring from propagating. He offered squishy theories about why this is so—nobody knew anything about genes then—and on how hybrids fit into his overarching theory of natural selection.

Nine years later, in a book that examined variation in domesticated animals, Darwin explored hybrids more closely—there was even a mention of ligers, which had first been bred in England in 1824. Darwin asserted that hybrids might inadvertently push back the evolutionary clock, resurrecting traits that were better left behind. He used the mixing of human racial groups as an example, stating that foreign travelers frequently remarked on “the degraded state and savage disposition of crossed races of man.”

Darwin’s hybrids-are-bad dictum became orthodoxy during evolutionary biology’s “modern synthesis,” in the 1930s and ’40s, which firmly connected genetics to natural selection. Harvard ornithologist Ernst Mayr, a leading neo-Darwinist, set the tone by dismissing hybrids as an evolutionary dead end.

Mayr’s verdict involved a surprisingly contentious question: What exactly is a species? Darwin had seen it as an arbitrary designation for animals that have similar physical features. Mayr came up with a concrete definition known as the “biological species concept.” A species, he declared, is a reproductively isolated group that can interbreed.

By this formula, a species was a fixed unit that was improved over time by forces like random mutation and mate selection, not by having “gene flow”—biologese for doin’ the nasty—with other species. “Species were rocks,” says Michael Arnold, an evolutionary biologist at the University of Georgia who studies hybridization in both plants and animals.

But maybe they aren’t. Arnold is part of a growing camp that sees species as more liquid than solid, and he rejects the idea that hybrids are always evolutionary losers just because they often can’t reproduce. “A lot of us have been hammering away on this for many years,” says Arnold. “They used to call us the Mongol hordes at their gates, but now we’re inside.”

Arnold is pushing a profound reconceptualization of evolution, one in which hybrids are more than bit players. Forget the tree of life, with new species neatly branching off from a common ancestor. It’s a web of life, and hybrids help genes flow in unexpected directions.

But what about their famous sterility? Some hybrids can reproduce, and Arnold stresses that rare events have an “overwhelming importance” in the evolutionary process. Hybrids often have desirable traits—some are more fit than either parent—and there have been instances when hybrids were able to find enough fertile hybrid partners to create a new species. This process appears to be under way right now in the U.S., involving a hybrid of the Pecos pupfish and the sheepshead minnow that has greatly multiplied and expanded its range. And some scientists contend that matings between gray wolves and coyotes thousands of years ago created an entirely new species: the red wolf.

More commonly, though, hybrids mate with one of their parent species, influencing the mix of what gets passed along to subsequent generations; essentially, they provide a bridge for genes to cross the species divide.

In a paper about hybridization and primate evolution that Arnold co-wrote last year for the journal Zoology, he offers several examples, including chimpanzees and bonobos. DNA studies suggest that these two great apes swapped genes sometime after separating from a shared ancestor at least 800,000 years ago. Arnold believes these ape cousins occasionally mated but that the resulting “bonanzees” did not establish a new species. Instead, they hooked up with either chimps or bonobos. Bonanzees ultimately vanished, but they left genetic footprints in the genomes of their descendants.

In addition to comparing genomes for evidence of unusual gene flow, scientists increasingly are using DNA analysis to confirm the existence of heretofore unknown natural hybrids, whose existence argues that this process still occurs. On April 16, 2006, a hunter in Canada’s Northwest Territories shot a polar bear whose fur had an orangish tint. Research showed that this animal had a grizzly bear father, making it the first confirmed wild pizzly ever found. (Pizzlies had been bred before in captivity.) In 2003, DNA analysis done by the Forest Service confirmed that five odd-looking felines found in Maine and Minnesota were bobcat-lynx hybrids, dubbed blynxes. Other DNA-confirmed hybrid mammals reported since 1999 include the forest/savanna elephant in sub-Saharan Africa, minks-polecats in France, and a sheep-goat in Botswana.

How much, then, do hybrids contribute to evolution? Nobody really knows. That’s what’s so exciting about these new DNA discoveries: The story is still unfolding.

 

A zorse (zebra + horse) named Zantazia

LEAVING ASIDE THEIR evolutionary import, there’s a simpler reason hybrids fascinate. Some are astonishingly beautiful.

In Ramona, California, Nancy Nunke raises zorses and zonkeys at a six-acre spread called the Spots ‘N Stripes Ranch, which mainly exists to breed zebras and miniature horses for show and for sale to private animal owners. After I pass through a security gate, Nunke greets me at her house and then points out her one zorse and two zonkeys, who are peeping at us from nearby corrals.

Nunke introduces me to her zorse, Zantazia, which, at seven months old, is still a zoal. This delicate creature has a sorrel coat, a horse’s long and thin face, and white stripes on her head, neck, torso, and legs. The offspring of a quarter horse mother and a Grevy’s zebra father, she may end up standing taller than both.

I reach out to stroke Zantazia’s neck, but she backs away. Nunke says zorses and zonkeys are friendly, but they have to set the pace. “It’s like if you walked down Main Street and someone threw his arms around you,” she says. “You’d say, ‘Hey, buddy, back off.’ “

Nunke has a soft spot for all “stripeys,” which she thinks are more playful and affectionate than horses. “Horses will rub on you because they have an itch,” she says. “A zebra will rub on you because he’s your best friend.” Zorses inherit the souls of zebras, she adds. “If they have one stripe, you train them exactly like you train a zebra. The z is totally in them.”

We walk over to meet the zonkey brothers, Zane and Zebediah, who have donkey faces and ears, caramel coats, and a dizzying array of black lines. “They’re the most striped zonkies in the world,” Nunke boasts. “What a good boy,” she says, patting Zane’s striped neck. Zane brays, and he looks so much like a zebra that his hee-haw startles me.

Nunke says some purists believe it’s wrong to breed hybrids, that they pollute the natural order. “Here’s how I feel about it,” she tells me, a bit of swagger in her voice. “Whatever God didn’t want to cross, he didn’t make genetically capable of crossing.”

OF ALL THE HYBRIDS that are theoretically possible, none shocks the mind like a cross between humans and apes, and there has been at least one attempt to create a humanzee. In 1910, Ilya Ivanovich Ivanov, a Russian pioneer in artificial insemination, proposed seeding a female chimpanzee with human sperm. At a zoology conference in Austria, he noted (oh-so quaintly) that this method would avoid the ethical dilemma of forcing the two species to actually have sex. Sixteen years later, with the backing of the Soviet Academy of Sciences, Ivanov traveled to Africa and gave it a try.

The details of Ivanov’s experiments only came to light in 2002, when a Rus-sian science historian, Kirill Rossiianov, produced a 39-page paper about the work. The study was published in English in the journal Science in Context, and when I came across it I was astonished. I struck up an e-mail correspondence with Rossiianov, then, late last year, met with him in Moscow. We spoke at a tea shop around the corner from Red Square, the outré topic making me feel like we were Cold War spies trading state secrets.

Over a ten-year period, Rossiianov was able to unearth Ivanov’s diaries and lab notes from the Soviet archives. According to Rossiianov, Ivanov and his son, a biochemistry student, set up a lab at the botanical gardens near Conakry, French Guinea. On the morning of February 28, 1927, they wrapped two female chimps in nets and inseminated them with sperm from a local man. On June 25, they inseminated another chimp with human sperm, this time using a special cage and knocking her out with ethyl chloride. None of the three became pregnant.

Rossiianov, a shy man, told me Ivanov’s work repulsed him. “What do you think about the ethical dimension of Ivanov’s experiments?” he asked. “Because, I dare say, I found them disgustful. Even now I find it terrible difficult to understand.”

And Ivanov had plans to take things further. He also asked Soviet authorities for permission to impregnate women in his own country with sperm from an orangutan named Tarzan, who lived at a primate station in the republic of Georgia. He got a green light, and at least one volunteer came forward, but Tarzan died before any tests took place. Ivanov, convicted of counterrevolutionary activities unrelated to these experiments, was sent to the gulag in 1930, ending his career.

So we still don’t know whether humans and chimps could successfully hybridize, but it may have happened in the distant past. A paper published in Nature last year offers compelling evidence that our ancestors had prolonged sexual relations with chimpanzees. The study, led by geneticist David Reich, of the Harvard Medical School, compares large stretches of DNA from humans and chimps.

The researchers, who contend that the two species diverged from a common forebear about 5.4 million years ago, found that the chimpanzee and human X chromosomes are more similar to each other than they are to any other chromosomes. The best explanation, they suggest, is that matings between chimps and early humans would have produced fertile female hybrids, who then mated with chimps themselves and had similar-enough X chromosomes to produce fertile male hybrids. They estimate that this went on for 1.2 million years after the initial split between the species. Eventually, only humans mated with the hybrids and the hybrids disappeared, leaving behind nothing but genetic traces in our chromosomes.

BHAGAVAN ANTLE, the liger trainer, keeps pretty busy—his many gigs include working parties and performing at a venerable Miami theme park called Parrot Jungle Island, where he displays a liger and a gigantic “crocosaurus,” a saltwater/Siamese crocodile. This entails a lot of animal shuttling, and Antle invited me to join him on a road trip from Myrtle Beach to Miami, where he would take a liger to a fundraiser at an exotic cat sanctuary and, later, a Super Bowl bash.

We meet at the Myrtle Beach facility, where Antle and his team lead Hercules the liger and two tigers into a trailer with small windows. Antle and I ride in an RV; joining us are three assistants and a diapered, nine-month-old orangutan named Apsara, who’s a hybrid, too. (She’s a blend of Bornean and Sumatran orangutans, which are different species.) The infant, which has a comical mess of wild orange hair, rides in a baby sling worn by an assistant. Except for the occasional meep meep, you wouldn’t know we’re rolling with an orang.

During the two-day trip to Miami, a truck-and-trailer hauling the big cats is always right behind us. We refuel at crowded truck stops, pull into strip malls to buy groceries, and even park one night behind a Holiday Inn. No one notices any of the exotic animals until we’re stopped at the agricultural checkpoint at the Florida state line. The officer, a good ol’ boy with slick hair and big sideburns, checks the paperwork and stumbles on the word liger. “What’s that?” he asks.

“A mix of lion and tiger,” Antle says.

“Those exist?”

Antle nods and takes out his business card, which shows him sitting with three tigers and Jay Leno. “Jay Leno!” says the officer. “That beats all!”

He waves us on without bothering to peek inside the trailer at one of the rarest creatures in the world. I guess Jay Leno is pretty much his favorite animal.