Buzz
The passenger pigeon was a legendary species, flying in immense numbers across North America, potentially in millions within a single flock. Their migration was once a spectacular event in nature. Sadly, the last living passenger pigeon died on 1 September 1914 at the Cincinnati Zoo. Geneticist Ben Novak leads an ambitious project aiming to revive the species through ‘de-extinction’. This involves cloning technology to transform extinct animal DNA into a fertilized embryo, carried by the nearest surviving relative – in this case, the abundant band-tailed pigeon – resulting in a live animal. Passenger pigeons are pioneers in this field, but many other extinct species are also being tested with this cutting-edge technology.
B
In Australia, the thylacine, commonly known as the Tasmanian tiger, is another extinct species genetic scientists are trying to revive. ‘No carnivore now inhabits Tasmania that fills the niche once occupied by the thylacine,’ explains Michael Archer of the University of New South Wales. He notes that since the thylacine's extinction, a ‘dangerously debilitating’ facial tumor syndrome has spread among Tasmanian devils, the island's other prominent inhabitant. Thylacines could have prevented this spread by controlling Tasmanian devil numbers. ‘Had that contagious cancer emerged earlier, it would have burned out in its initial region. The return of thylacines to Tasmania could ensure that devils never face such risks again.’
C
If extinct species can be revived, can humanity begin to repair the damage it has inflicted on the natural world over the millennia? ‘De-extinction suggests we can reverse this process by bringing back species that no longer exist,’ says Beth Shapiro of the University of California Santa Cruz Genomics Institute. ‘I'm not convinced it's feasible. It's impossible to resurrect something exactly identical to a species extinct for so long.’ For long-extinct species, a more practical approach involves using existing species' DNA as a template, into which extinct animal DNA strands are inserted to create something new – a hybrid based on the living species, resembling or behaving like the extinct animal.
D
The fundamental question raised by this intricate process and its uncertain outcomes is: what is the actual purpose of this technology? ‘Our goal has always been to replace extinct species with suitable alternatives,’ explains Novak. ‘Compared to the social behavior of passenger pigeons, which created 10,000 nests per hectare, band-tailed pigeons today scatter and create only one or two nests per hectare. Since the disappearance of passenger pigeons, ecosystems in the eastern US have suffered. The absence of disturbance caused by thousands of passenger pigeons nesting and breaking branches has resulted in minimal regrowth, leaving forests stagnant and inhospitable to the plants and animals that evolved to regenerate forests after disturbances. According to Novak, a hybrid band-tailed pigeon incorporating the nesting habits of passenger pigeons could potentially reintroduce forest disturbance, thereby creating habitats necessary for numerous native species to thrive.
E
Another prominent candidate for this technology is the woolly mammoth. George Church, professor at Harvard Medical School and leader of the Woolly Mammoth Revival Project, has focused on enhancing cold resistance, the primary difference between the extinct woolly mammoth and its closest living relative, the Asian elephant. By identifying the genetic traits that enabled mammoths to survive the icy tundra climate, the project aims to reintroduce mammoths or a mammoth-like species to the area. ‘My top priority is conserving the endangered Asian elephant,’ Church emphasizes, ‘expanding its range into the vast ecosystems of the tundra. Key adaptations would include smaller ears, thicker hair, and additional insulating fat to minimize heat loss in the tundra – traits observed in the now-extinct woolly mammoth.’ Repopulating the tundra and boreal forests of Eurasia and North America with large mammals could also aid in reducing carbon emissions, as elephants create paths through snow and topple trees, encouraging grass growth. This growth could lower temperatures and mitigate emissions from thawing permafrost.
F
While the idea of reviving extinct animals captures the imagination, it is undoubtedly easier to focus on preserving existing species threatened with extinction. ‘Many of the technologies associated with de-extinction can serve as forms of “genetic rescue,”’ explains Shapiro. She prefers to redirect the discussion toward how this emerging technology could deepen our understanding of why various species became extinct and, consequently, how genetic modifications might prevent future mass extinctions. ‘There’s also a significant moral hazard in doing nothing,’ she continues. ‘We know that current efforts are insufficient, and we must be prepared to take calculated risks.’
Questions 14-17
14 a reference to how further disappearance of multiple species could be avoided.
15 explanation of a way of reproducing an extinct animal using the DNA of only that species.
16 reference to a habitat which has suffered following the extinction of a species.
17 mention of the exact point at which a particular species became extinct.
Questions 18-22
The project to revive the woolly mammoth
Professor George Church and his team are trying to identify the 18…… which enabled mammoths to live in the tundra. The findings could help preserve the mammoth’s close relative, the endangered Asian elephant.
According to Church, introducing Asian elephants to the tundra would involve certain physical adaptations to minimise 19…… To survive in the tundra, the species would need to have the mammoth-like features of thicker hair, 20…… of a reduced size and more 21……
Repopulating the tundra with mammoths or Asian elephant/mammoth hybrids would also have an impact on the environment, which could help to reduce temperatures and decrease 22……
Questions 23-26
23 Reintroducing an extinct species to its original habitat could improve the health of a particular species living there.
24 It is important to concentrate on the causes of an animal’s extinction.
25 A species brought back from extinction could have an important beneficial impact on the vegetation of its habitat.
26 Our current efforts at preserving biodiversity are insufficient.
List of People
A Ben Novak
B Michael Archer
C Beth ShapiroResponse:
- F (Đoạn F, “…make genetic modifications which could prevent mass extinctions” → Việc biến đổi gen giúp ngăn chặn tuyệt chủng ở nhiều loài)
- A (Đoạn A, “The basic premise involves using cloning technology to turn the DNA of extinct animals into a fertilised embryo,…” → dùng công nghệ biến đổi DNA của chim)
- D (Đoạn D, “Since the disappearance of this key species, ecosystems in the eastern US have suffered, … help regenerate the forest after a disturbance.” → Môi trường sống làm ảnh hưởng tới sự sống còn của nhiều loài động vật)
- A (Đoạn A, “Sadly, the passenger pigeon’s existence came to an end on 1 September 1914” → Thời điểm chính xác loài chim bồ câu bị tuyệt chủng)
- Genetic traits (Đoạn E, “By pinpointing which genetic traits made it possible for mammoths to survive the icy climate of the tundra,…”)
- Heat loss (Đoạn E, “…all for the purpose of reducing heat loss in the tundra,…”)
- Ears (Đoạn E, “Necessary adaptations would include smaller ears,…)
- (Insulating) fat (Đoạn E, “and extra insulating fat,…)
- (Carbon) emissions (Đoạn E, “…could also be a useful factor in reducing carbon emissions…”)
- B (Đoạn B, “explains Michael Archer …Thylacines would have prevented this spread because they would have killed significant numbers of Tasmanian devils.)
- C (Đoạn F, “…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,…”)
- A (Đoạn D, “According to Novak, a hybridized band-tailed pigeon, with the added nesting habits of a passenger pigeon, …for a great many other native species to thrive.)
- C (Đoạn F, “‘We know that what we are doing today is not enough, and we have to be willing to take some calculated and measured risks.’”)
