Beasts that could come back from extinction

Five films on, Jurassic Park still has us captivated by the idea of humans coming face-to-face with our planet's most terrifying former inhabitants. But the fantasy of resurrecting a dinosaur from DNA in the belly of an amber-trapped mosquito is a long way from reality. Leading de-extinction scientists say making use of genetic material more than a million years old won't be possible.

Since the last male northern white rhino — a 45-year-old called Sudan — died earlier in 2018, elderly females Najon and Fatu are the last of their kind. But scientists hope that embryos in deep freeze could bring the "functionally extinct" species back from the edge. They were created in vitro from the sperm of a deceased male northern white and the eggs of the closely related southern white.

When the dodo — a fatally trusting and tasty bird — disappered from Mauritius in the 17th century, few believed mankind could extinguish the life of an entire species. Only after 19th century naturalist Georges Cuvier proved extinction was possible did the dodo became a symbol of that destructive power. Now, the hunt is on for dodo DNA, in the hope we may also prove our power to resurrect.

By the time the last Pyrenean ibex Celia died in 2000, scientists had already gathered and frozen her tissue cells. Three years later, a goat gave birth to Celia's clone, created by injecting her DNA into a goat's egg. In fact, dozens of hybrid eggs were implanted. Only seven animals became pregnant, and one carried to full term — and the resurrected ibex survived only a few minutes after birth.

This is Martha, the last passenger pigeon, who died in 1914. The plump North American birds were a favorite for the plate, and hunting combined with deforestation wiped them out even as conservationists warned of their senseless demise. Revive & Restore, an organization that promotes "de-extinction," sees the passenger pigeon as the perfect model project to show resurrection science's potential.

European colonists in Australia put a bounty on the head of the thylacine, or Tasmanian tiger, a marsupial apex predator. The last known member of the species died in Hobart Zoo in 1936. Now, scientists have decoded the animal's entire genome from a joey preserved in ethanol, and hope to insert its genes into the DNA of its closest surviving relative, a diminutive marsupial called the numbat.

The most impressive species with any chance of making a comeback is the woolly mammoth, whose closest living relative is the Asian elephant. Scientists at Harvard University say the ice-age giants could play a role in slowing permafrost melt and, therefore, climate change. But their "Pleistocene Park" concept would need 80,000 animals to have any real impact — pure science fiction, say critics.

The auroch once roamed the length and breadth of Eurasia, but hunting and habitat loss wiped them out close to 400 years ago. Yet their descendents — domesticated cattle — live on, and "back-breeding" programs have tried to resurrect the auroch by selecting for characteristics of the wild ancestor. An early German attempt resulted in Heck cattle, which have been reintroduced to parts of Europe.

We once shared the planet with other human species, like the Neanderthal, with whom we even interbred. Many of us still carry Neanderthal DNA. But we are also prime suspects in their extermination. What would it be like to confront the relations we once wiped out? Scientists are growing homo sapiens-Neanderthal hybrid brain matter in the lab to examine the differences between them and us.