Everyone’s favorite extinct-but-maybe-not animal just got a strange and unexpected new branch on its evolutionary chain. Genetic researchers studying the extinct Tasmanian tiger or thylacine have discovered that the creature shared more than just its uncanny looks (minus the stripes) with the wolf (Canis lupus) – they share DNA elements that explains their surprising similarities despite evolving independently for over 160 million years. Will this new information help bring the thylacine back from extinction? Or does it bode poorly for the future of the similarly threatened and hunted wolf?
“The thylacine and placental canids such as wolves, dogs and foxes, are perhaps the most striking example of convergent evolution. Through this process, distantly related animals can evolve similar forms in response to shared environmental challenges.”
In a recent article in Pursuit (published by the University of Melbourne), Dr Charles Feigin of Princeton University and the University of Melbourne describes the results of a study he conducted with fellow professor Andrew Pask which was published in the journal Genome Research. He points out the obvious puzzling question – how did a marsupial and a placental (animal whose fetus is carried in the uterus) evolve to look and behave in such a strikingly similar manner? The simple answer is “convergent evolution” – the process by which distinct species in completely different environments can develop similar traits not found in their last common ancestor. In the case of the wolf and the Tasmanian tiger, both evolved to become top-of-the-heap predators with “nearly identical skull shapes with similar biomechanical properties.”
How did this happen? After creating the first genome sequence from the DNA of a thylacine in 2018, Feigin and Pask found no clues as to why Thylacinus cynocephalus (roughly translated as ‘pouched dog-head’) was so close to Canis lupus. They then turned to non-coding DNA which is now known to regulate genes during development. There they found “hundreds of non-coding DNA elements in the thylacine and wolf.”
“These elements, called ‘TWARs’ (thylacine-wolf accelerated regions), show evidence of natural selection in both species, but lay outside of the much-better understood protein-coding regions of the genome. TWARs were particularly abundant near genes involved in the development of bone, cartilage and muscles of the facial region.”
Aha! This discovery shows that genes played a much more important role in the development of the two species than natural selection or environmental influence and changes. And, because non-coding DNA is less influenced by mutations, it preserved these common traits right up until current times – well, at least until the thylacine became extinct in 1936.
Is this a big deal?
“Little was documented about the thylacine’s hunting or social behaviours before their untimely extinction, but these signatures of convergent evolution present the tantalising possibility that these distant cousins may have shared more than just their looks.”
Future researchers may use these results to fill in the gaps in the thylacine’s evolutionary history. Will it help bring them back? That could be tough, since genetic scientists would still have to deal with the major differences between these dog-headed marsupials and placentals. Will it help bring back the Tasmania tiger? Well, knowing it’s closer to the wolf than once thought, it might help figure out where they’re hiding.
There’s always hope.