A research team has, for the first time, produced the complete DNA sequence of the extinct Thylacine, also known as the “Tasmanian tiger.”
An international team of researchers led by associate professor Andrew Pask from the University of Melbourne used DNA from the 106-year-old preserved remains of a juvenile thylacine or Tasmanian tiger to sequence the animal’s genome, making it one of the most complete genetic blueprints for an extinct species.
The last known Thylacine died at a zoo in Hobart in 1936. The dog-sized creatures with tawny-brown fur and striped hindquarters originally lived in both Tasmania and the Australian mainland, though it was already rare before British settlers began arriving in the late 18th century. The animals got a bad reputation as killers of cattle and sheep and … Australia. Sheep. Extinction. Just about that fast.
By the 1830s, the animal was probably driven to extinction on the Australian mainland. Even in Tasmania, the animals were likely endangered from the start, and sightings were rare. But bounties were established over the perceived threat to sheep. Just over 2,100 bounties were paid out, the last one in 1930. In 1936, the Australian government at last moved to protect the Thylacine—59 days before the last captive animal died.
The genetics of the animal reflect that long period of deep, near-extinction level stress.
The first full genetic blueprint of the long-extinct thylacine has revealed the animal suffered from genetic weakness well before it was isolated on Tasmania 10,000 to 13,000 years ago. …
While overhunting was “without doubt” responsible for the animal’s extinction in 1936, Pask said its genetic weakness would have made it more susceptible to disease had it survived.
The genetic evidence suggests that Thylacine numbers had been dropping for a long period. Changes in genes can act like a clock, and the research team has a pretty good idea of how long the “tigers” had been on the decline.
“But what we found is that the population declined about 70,000 years ago, long before it was isolated meaning it probably had more to do with changes in the climate back then.”
Many animals, particularly predators, fall into a trap where reduced numbers result in lowered genetic diversity and greater susceptibility to disease. When the last mass extinction event occurred about 12,000 years ago, cheetahs are one of the species that just squeaked through. Which still shows in their genes today.
This event caused an extreme reduction of the cheetah’s genetic diversity, known as a population bottleneck, resulting in the physical homogeneity of today’s cheetahs. Poor sperm quality, focal palatine erosion, susceptibility to the same infectious diseases, and kinked tails characteristic of the majority of the world’s cheetahs are all ramifications of the low genetic diversity within the global cheetah population.
That 70,000 years ago number—the point at which Thylacines took a hit—is particularly interesting for another species that had trouble about that time.
The number of early humans may have shrunk to as low as just 2,000 before it began to rise again in the early Stone Age, an extensive new genetic study suggested yesterday.
The close brush with extinction for human beings came around 70,000 years ago, according to the report published in the American Journal of Human Genetics.
Both humans and Thylacines made it, but the number of tigers that came through the bottleneck may have been small enough to leave the species genetically fragile ever since.
Though “tigers sightings” regularly make the news both in Tasmania and elsewhere in Australia, there’s been no hard evidence for any surviving animals since 1936. In 1980, the Thylacine was officially declared extinct.
Sequencing the DNA of the vanished tiger might be taken as the first step in resurrecting the species, but there are some real difficulties. The closest surviving relative of the Thylacine is the famous Tasmanian devil (which also displays low genetic diversity that leaves them open to a godawful disease in the form of a communicable cancer). But devil’s are much smaller than were Thylacines. Finding an animal to host Thylacine “joeys” might be extremely difficult, even if they could be produced.
In 1933, that last Thylacine was filmed for a total of 62 seconds. That. Some photos of other zoo residents, and images of hunters showing off their kills—that’s what we have.