Urban expansion and hunting have pushed chimpanzees, humanity's closest relative in the animal kingdom, into shrinking pockets of wilderness, researchers said Tuesday following a three-day meeting in the German city of Leipzig.

More than 40 scientists — with a combined 300 years of experience — called for action to protect the only animal whose DNA is a 98% match with humans

Their meeting marked the 40th anniversary of a long-term research and conservation project on chimpanzees in the Tai National Park in Ivory Coast.

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'Living in forest ghettos'

"Over the decades that we have been working with wild chimpanzee communities, we have all seen our study groups become isolated," the researchers said in a statement. "Chimpanzees are being reduced into living in forest ghettos."

All four sub-species of the African primate are threatened with extinction, with at least one — the western chimpanzee — declining in number by more than 80% over three generations.

There are just thousands of chimps for three of the sub-species, and about 250,000 for the eastern chimpanzee, found mainly in the Democratic Republic of Congo.

Western chimpanzees have already been completely lost in Burkina Faso, Benin, Gambia, and possibly Togo.

Habitat loss to blame

The researchers said the main threat to chimps and other large mammals is habitat loss.

While Africa does have large sections of undisturbed savannah and forest, these areas are diminishing quickly due growing cities, mining, deforestation, and industrial agriculture.

The continent's human population of more than 1.2 billion is expected to double by mid-century, and could top 4 billion by the end of the century.

"Forty years ago [in Tai National Park in Ivory Coast], we drove 100 kilometers (60 miles) on a mud road to reach the park boundaries while encountering chimpanzees and elephants," said Christopher Boesch, a professor at the Max Planck Institute for Evolutionary Anthropology in the German city of Leipzig, in the statement. "Nowadays, you have to reach the park boundaries to see the first patch of forest."

Human encroachment and the hunting of chimpanzees for "bush meat" has also caused changes in the social life and behavior of the animals, Crickette Sanz, an associate professor at Washington University in Missouri who has worked for decades in the Republic of Congo's Goualougo Triangle, told French news agency AFP.

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'We are allowing them to become extinct'

The last common ancestor of humans and chimpanzees lived about seven million years ago.

"We did not evolve from bonobos or chimpanzees but we share with them a common ancestry," Martin Surbeck, a primatologist at the Max Planck Institute for Evolutionary Anthropology in Leipzig told AFP.

"If we, in our travels in space, should encounter a creature that shared 98 percent of our genetic makeup, think of the money we would spend to study this species," he said. "Such creatures exist on Earth and we are allowing them to become extinct."

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