Tigers, the largest of the world’s cats, are the heart and soul of Asia’s jungles, grasslands, and deserts. They’re so adaptable that they even thrive in the frigid Himalayan foothills—and they are the dominant predator, literally the kings and queens, of every ecosystem they inhabit. But Asia’s exploding human population is eating away their forest home, and both tigers and their prey have been caught in the crosshairs (瞄准器) , killed in vast numbers by hunters and more recently, by poachers.
In just 100 years’ time, we humans have engineered their grand-scale death. A century ago, more than 100,000 tigers roamed across 30 nations, from Turkey to Siberia, throughout Southeast Asia down to the tip of Indonesia. Today, they hang on in just 12 countries; though they’re the national animal of six nations, they’ve vanished from two of them, North and South Korea. They’ve disappeared from 93 percent of their former range; just 42 breeding populations remain, scattered across the continent. Half of all our wild tigers live in India.
Recently, the Smithsonian Conservation Biology Institute yzed the genetic vigor of tigers in a string of reserves across central India, where I just spent three weeks. One of them, Pench Tiger Reserve, is a 100-square-mile (257-square-kilometer) patch that looks like an illustration from The Jungle Book: groves of towering bamboo, big-leafed teak trees and "strangler fig" banyans filled with acrobatic langur monkeys. But Pench is essentially a leafy island. It’s hard to believe that a century ago, this was mostly unbroken forest. Today it, (like many parks, especially in India) is being squeezed by an encroaching, crowded sea of humanity. These parks are bordered by a patchwork of rice paddies, crop fields, bordering on villages, cities, and all sorts of development. The surrounding land is segmented by roads, railways, scarred by massive mines and other barriers that render it erous and virtually impassable for these wide-ranging predators.
Researchers found that in Pench and other reserves that lacked corridors connecting them to other forests, tigers were far more inbred. Those cats had 47 to 70 percent less gene flow, and as we know from the medical history of European royalty, inbreeding (近亲繁育) does not create the healthiest bloodlines.
Tigers have lived in these lands for thousands of years; like all modern cats, they originated in Southeast Asia. The great roaring cats, Panthera were the first to branch off the cat family tree 10.8 million years ago. It’s a group that includes tigers, lions, leopards, jaguars and snow leopards.
According to the passage, which of the following is CORRECT