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更新时间:2018-4-16 20:07:36 来源:纽约时报中文网 作者:佚名

The increasingly realistic prospect of 'extinct animal' zoos

A traveller marvelling at snow leopards in a conservation park. A foodie who wants to taste pangolins without breaking the law. A game hunter tracking a black rhino which will be replenished after the kill.


To some people, these scenarios seem like dystopian nightmares. To others, they’re exciting prospects. And as the science advances, they may be more feasible than they might first appear. Some researchers are even exploring how animal cloning could change the tourism industry by 2070.


State of the art


A Jurassic Park situation of dinosaurs once more roaming the Earth remains a fantasy. De-extinction is incredibly challenging and it’s not clear whether dinosaur DNA even can be recovered. With current technology, DNA samples only remain useful for about 1 million years – so theoretically we could clone a Neanderthal, but not a Triceratops last seen 65 million years ago.


Woolly mammoth DNA is more accessible. We have flash-frozen mammoth samples and can implant the genetic material into elephants, which are genetically similar. We can’t actually bring mammoths back in habitats resembling their original ones, though, where they could breed naturally.


But scientists might eventually be able to do that with other species that died out more recently than mammoths – like passenger pigeons. This would involve mapping the entire passenger pigeon genome, then mutating a common pigeon’s genome so that it’s akin to a passenger pigeon’s. Voilà: a cloned extinct species.


The science has come a long way since Dolly the sheep was cloned in 1996, says University of Connecticut biotechnology professor Xiuchun (Cindy) Tian, who is working on reactivating nucleus-based DNA through cloning.

康乃狄克大学生物技术教授田秀春(Cindy Tian)认为,自1996年克隆羊多莉诞生以来,科学已经有了长足的进步。目前她正在研究通过克隆在分子层面重新启动DNA。

Controversial conservation efforts are underway to implant white rhino embryos into a surrogate. By one estimate a woolly mammoth-elephant hybrid is only a few years away. In Tian’s estimation, if there were sufficient political will and funding, it would only take 10 years to reach a situation where zoos are populated with rare and even endangered animals.


We’re already partway there. In 2000, the San Diego Zoo planned to display a cloned gaur (Indian bison) named Noah, although he died of an infection after two days. The zoo later housed Jahava, a banteng (a type of wild cattle from South East Asia), for seven years, until Jahava broke a leg and was euthanised. Jahava and Noah were both cloned using cells from San Diego’s Frozen Zoo: a collection of frozen skin samples from endangered animals.


So the main obstacles may be financial and political, rather than scientific, Tian says.


For one thing, mortality rates for cloned animals are initially very high. Reasons aren’t entirely clear, but likely include reprogramming errors: essentially, the donor egg cell’s nucleus holds on to a kind of genetic memory and resists the replacement with the new genetic material. Animals cloned through this process, known as somatic cell nuclear transfer, “have to survive that first shock after birth”, Tian says. “If they do survive, they’re generally healthy.”

首先,克隆动物初期死亡率是非常高的。原因尚不完全清楚,但可能包括重新编码细胞时发生的错误。究其根本,供体卵细胞的细胞核持有一种遗传记忆,会抵制新遗传物质的替代。田教授说,克隆动物涉及到体细胞核移植,这一过程非常艰难,克隆出来的动物"必须熬过出生后的第一个难关才能存活", "如果能挨过这一关,他们通常都会健康成长" 。

There are ethical concerns about producing animals with a high chance of early death or stress. Still, similar questions might be raised about producing livestock in general. And the success rates are increasing. In 1996, scientists used 277 cloned embryos to get one successful Dolly. “Now if you do cloned cattle, you can transfer 100 cattle cloned embryos and get about 10–20 cloned animals born,” says Tian. "That’s an amazing change.”

人们对于克隆动物较高的早期死亡率和存活压力怀有伦理方面的担忧。同样的问题也存在于一般牲畜的生产过程中。不过成功率确实在提高。早在1996年时,科学家使用277个克隆胚胎才能成功培育一只多莉羊。 "现在如果你生产克隆牛,你可以向100头牛移植克隆胚胎,并获得约10-20只出生的克隆动物,"田教授赞叹道,"这是一个了不起的变化。"

Even so, the higher mortality rates mean that cloning remains very expensive. The only current productive use of animal cloning is for prize beef bulls, whose genetic stock is valuable to farmers. Tian estimates that the cost of cloning a single bull is at least $15,000. Cloning wild or endangered animals would be even more expensive, as we have less information about them and fewer specimens to use as tests.


Clone ranger


So from a scientific standpoint, it’s well within the realm of possibility to clone endangered animals (and, to a lesser extent, recently extinct ones). If that happens, most of us won’t have much contact with these cloned endangered animals on a daily basis. But one area that might allow non-scientists to interact with clones is in tourism for wealthy individuals.


If you think your Instagram feed already is full of people showing off novel, specialised travel experiences, that will only increase, according to experts like Daniel Wright, tourism management lecturer at the University of Central Lancashire and author of a paper on cloning and tourism. Jaded travellers might pay through the nose to hunt cloned animals in South Africa, eat cloned animals in Japan, or spot clones of endangered animals while on safari in the US.

赖特(Daniel Wright)是中央兰开夏大学旅游管理专业讲师,并撰写过一篇关于克隆与旅游的论文。他认为,人们的社交网站首页会越来越多地被各种新颖、特别的旅游体验所占据。已经厌倦常规旅行的游客可能会出高价在南非捕猎克隆动物,在日本品尝克隆动物,或是在美国探险的途中观赏克隆的濒危动物。

Right now, adventurous eaters in Japan eat fugu although certain species are threatened by overfishing (and despite the poisonous nature of these pufferfish). Controversially, the Namibian government auctions off several permits each year to hunt the endangered black rhino, arguing that the money is essential for conservation programmes and only non-breeding rhinos can be hunted. Cloning could make both experiences accessible to more visitors.


And of course zoos and safari parks around the world already display endangered animals. Many of them participate in biodiversity programmes aiming to keep endangered animals from going fully extinct, or from becoming dangerously inbred as there are so few, for instance, black-footed ferrets.


So it could be argued that applying cloning technology for similar tourism purposes is, while expensive, not hugely different from an ethical standpoint. If it’s harmful to support a zoo containing carefully bred animals that will spend their lives in captivity, cloning doesn’t change that.


One person paying close attention to these debates is Carrie Friese, a London School of Economics sociologist and the author of Cloning Wild Life. Friese says that in traditional zoos, animals are the stars; they’re the reasons people come. But in future conservation parks featuring cloned animals, she envisions the technology rather than the animals being the focus. A de-extinction park, for instance, would be about celebrating human ingenuity as much as marvelling at the animals: “The appeal is the ability to bring the passenger pigeon back, as much as seeing the passenger pigeon.”

伦敦政治经济学院社会学家,《克隆野生动物》(Cloning Wild Life)作者弗里斯(Carrie Friese)一直密切关注这些争论。弗里斯说,在传统的动物园里,动物是焦点,人们为它们而来。然而她预想,在未来以克隆动物为特色的保护公园中,焦点会是克隆技术而非仅仅动物本身。例如在一个灭绝动物复活园中,人们在观赏动物的同时也会庆祝人类的聪明才智:"其吸引力不仅在于观赏候鸽,也在于惊叹人类复活候鸽的能力。"

Like Tian, Friese can see these experiences drawing tourists. For instance, some opinion polls show that Americans are more supportive of cloning technology when it’s used for conservation than for any other purpose.


The two researchers can also imagine people cloning endangered animals for food. Tian’s research has shown that the meat and milk produced by cloned bovines is safe for human consumption and is largely indistinguishable from non-cloned animal products. She recalls sampling beef from a cloned black bull in Japan, “It was delicious. Many people stayed in line for seconds.” But food supply isn’t the main use for animal cloning at the moment, and some people may be anxious about the safety of eating cloned food.


Thus, the most likely scenario for future cloned-animal tourism remains a (non-Jurassic) park. Yet as Friese points out, cloning practices raise complicated questions about authenticity and ethics. Would a cloned Pyrenean ibex, whose nuclear DNA is combined with that of domestic goats, be a true ibex? Could a cloned animal from a wild species be considered wild itself? And if zoos and safari parks with access to the latest biotechnology become full of cloned animals in the future, what would the impact be on low-income countries that currently depend on tourism based around wild animals?


These aspects are foggy, but one thing is clear. The hype around a costly biotechnological process shouldn’t entirely displace habitat preservation and tried-and-true conservation practices. As Wright puts it, “humans should support and implement measures that aim for preservation of natural environments and to ensure animals and species do not go extinct.”