剑桥雅思15Test2Passage2阅读原文翻译 Should we try to bring extinct species back to life 复活已灭绝的物种
剑桥雅思15 Test2 Passage2阅读原文翻译
The passenger pigeon was a legendary species. Flying in vast numbers across North America, with potentially many millions within a single flock, their migration was once one of nature’s great spectacles. Sadly, the passenger pigeon’s existence came to an end on 1 September 1914, when the last living specimen died at Cincinnati Zoo. Geneticist Ben Novak is lead researcher on an ambitious project which now aims to bring the bird back to life through a process known as ‘de-extinction’. The basic premise involves using cloning technology to turn the DNA of extinct animals into a fertilised embryo, which is carried by the nearest relative still in existence – in this case, the abundant band-tailed pigeon – before being born as a living, breathing animal. Passenger pigeons are one of the pioneering species in this field, but they are far from the only ones on which this cutting-edge technology is being trialled.
候鸽是一种传奇物种。它们的迁徙曾经是自然界最为壮观的景象之一。大量的候鸽飞越北美上空，仅仅一群鸽子里可能就有数百万只。令人悲伤的是，1914年9月1日，最后一只活着的候鸽在辛辛那提动物园死去，该物种也随之灭绝。基因学家Ben Novak是一个宏伟项目的首席研究员。该项目如今致力于通过一种叫做“逆转灭绝”的过程复活这种鸟类。其基本操作为利用克隆技术将已灭绝动物的DNA放入一颗受过精的胚胎中。然后由其仍然存活着的、血缘上最为亲近的物种 – 这一案例中使用的是数量丰富的斑尾鸽 – 孕育出活生生的、能够呼吸的动物。
In Australia, the thylacine, more commonly known as the Tasmanian tiger, is another extinct creature which genetic scientists are striving to bring back to life. ‘There is no carnivore now in Tasmania that fills the niche which thylacines once occupied,’ explains Michael Archer of the University of New South Wales. He points out that in the decades since the thylacine went extinct, there has been a spread in a ‘dangerously debilitating’ facial tumour syndrome which threatens the existence of the Tasmanian devils, the island’s other notorious resident. Thylacines would have prevented this spread because they would have killed significant numbers of Tasmanian devils. ‘If that contagious cancer had popped up previously, it would have burned out in whatever region it started. The return of thylacines to Tasmania could help to ensure that devils are never again subjected to risks of this kind.’
在澳大利亚，袋狼是另外一种科学家正在努力复活的已灭绝物种。它更广为认知的名字是塔斯马尼亚虎。“塔斯马尼亚如今没有任何一种物种能够填补袋狼曾经的位置”，新南威尔士大学的Michael Archer解释到。他指出，在袋狼灭绝后的这几十年里，一种十分危险的面部肿瘤症状传播开来，威胁到该岛屿上另外一种臭名昭著的原住民 – 袋獾 – 的生存。袋狼本可以阻止这场传播，因为它们文章来自老烤鸭雅思会捕杀大量的塔斯马尼亚袋獾。“如果这种传染性的癌症之前爆发出来，无论它从哪个区域开始，其苗头很快就会熄灭。袋狼在塔斯马尼亚的回归有助于确保袋獾永远不再遭受这类风险的影响”。
If extinct species can be brought back to life, can humanity begin to correct the damage it has caused to the natural world over the past few millennia? ‘The idea of de-extinction is that we can reverse this process, bringing species that no longer exist back to life,’ says Beth Shapiro of University of California Santa Cruz’s Genomics Institute. ‘I don’t think that we can do this. There is no way to bring back something that is 100 per cent identical to a species that went extinct a long time ago.’ A more practical approach for long-extinct species is to take the DNA of existing species as a template, ready for the insertion of strands of extinct animal DNA to create something new; a hybrid, based on the living species, but which looks and/or acts like the animal which died out.
如果已灭绝的物种能够重现于世的话，人类能开始修复它在过去几千年里给自然界造成的破坏吗？“逆转灭绝的想法在于我们可以扭转这一过程，复活那些已经不再存在的物种”，加利福尼亚大学圣克鲁兹分校基因组学研究所的Beth Shapiro这样说道。“我不认为我们可以达成这一目标。复活之后的东西不可能与很久以前已经灭绝的物种百分百一致”。对于灭绝已久的物种来说，更为实际的方法是将现存物种的DNA当作底板，在其中插入已灭绝动物的DNA片段，从而创造出崭新的物种 – 一种基于现存物种的杂交种，然而看起来或者行动起来却类似已灭绝的动物。
This complicated process and questionable outcome begs the question: what is the actual point of this technology? ‘For us, the goal has always been replacing the extinct species with a suitable replacement,’ explains Novak. ‘When it comes to breeding, band-tailed pigeons scatter and make maybe one or two nests per hectare, whereas passenger pigeons were very social and would make 10,000 or more nests in one hectare.’ Since the disappearance of this key species, ecosystems in the eastern US have suffered, as the lack of disturbance caused by thousands of passenger pigeons wrecking trees and branches means there has been minimal need for regrowth. This has left forests stagnant and therefore unwelcoming to the plants and animals which evolved to help regenerate the forest after a disturbance. According to Novak, a hybridised band-tailed pigeon, with the added nesting habits of a passenger pigeon, could, in theory, re-establish that forest disturbance, thereby creating a habitat necessary for a great many other native species to thrive.
Another popular candidate for this technology is the woolly mammoth. George Church, professor at Harvard Medical School and leader of the Woolly Mammoth Revival Project, has been focusing on cold resistance, the main way in which the extinct woolly mammoth and its nearest living relative, the Asian elephant, differ. By pinpointing which genetic traits made it possible for mammoths to survive the icy climate of the tundra, the project’s goal is to return mammoths, or a mammoth-like species, to the area. ‘My highest priority would be preserving the endangered Asian elephant,’ says Church, ‘expanding their range to the huge ecosystem of the tundra. Necessary adaptations would include smaller ears, thicker hair, and extra insulating fat, all for the purpose of reducing heat loss in the tundra, and all traits found in the now extinct woolly mammoth.’ This repopulation of the tundra and boreal forests of Eurasia and North America with large mammals could also be a useful factor in reducing carbon emissions – elephants punch holes through snow and knock down trees, which encourages grass growth. This grass growth would reduce temperatures, and mitigate emissions from melting permafrost.
这一技术另外一个呼声很高的备选是猛犸象。哈佛医学院教授，同时也是猛犸象复活项目的负责人George Church一直关注防寒抗冻。这是已灭绝的猛犸象和它亲缘最近的现存物种-亚洲象之间的主要差别。通过定位使猛犸象能够在冻土寒冷气候中存活下来的基因特质，该项目的目标是让猛犸象，或者类似猛犸象的物种重新回到该区域。“我的最高优先目标是保护濒临灭绝的亚洲象”，Church说，“将它们的活动范围扩展到冻原巨大的生态系统中。必要的调整包括更小的耳朵，更厚的毛发，以及额外的保温脂肪层。所有这些都是为了减少冻土上的热量流失，而所有这些特质都能够在如今已经灭绝的猛犸象身上找到“。这一向欧亚大陆和北美洲的冻土与北部森林重新输送大型哺乳动物的计划也有助于减少碳排放 -大象会在雪地上踩出洞来，还会撞倒树木，从而刺激草皮生长。而草皮的生长会降低温度，缓解永冻层融化的相应排放。
While the prospect of bringing extinct animals back to life might capture imaginations, it is, of course, far easier to try to save an existing species which is merely threatened with extinction. ‘Many of the technologies that people have in mind when they think about de-extinction can be used as a form of “genetic rescue”,’ explains Shapiro. She prefers to focus the debate on how this emerging technology could be used to fully understand why various species went extinct in the first place, and therefore how we could use it to make genetic modifications which could prevent mass extinctions in the future. ‘I would also say there’s an incredible moral hazard to not do anything at all,’ she continues. “We know that what we are doing today is not enough, and we have to be willing to take some calculated and measured risks.’