The last living Tasmanian Tiger (Thylacinus cynocephalus) died in Hobart Zoo, Australia in 1936, and has in many ways become one of the flagship species for human-caused extinction. I wrote a post about the probability of them still being alive in remote parts of Tasmania about a year ago, so if you are one of those people who still think they are alive, you should read that. I always wanted to believe that they were still out there, but these days it seems impossible.
Anyway, today’s post is about the genome sequencing of the Tasmanian Tiger and what we have learned from it!
A painting of two Tasmanian tigers. Image is Public Domain.
The Tasmanian tiger was a carnivorous marsupial that used to live in Australia and on the Australian island Tasmania back in the days, but were first driven to extinction on mainland Australia about 3,000 years ago, and later on Tasmania as well. Like most other extinct carnivores, it was hunted because farmers did not like having them around.
We humans were therefore directly responsible for their demise, but as mentioned at the top of the post, a lot of people still believe that there are a few Tasmanian tigers left on Tasmania, hidden out in the vast forests there. Ecologically it fills the same niche as the red fox, and preyed upon small mammals and birds.
What does it mean to sequence a genome?
When we sequence a genome, all the base-pairs of the entire DNA of a single animal is known. This gives us a very long string of A, G, T and Cs if you remember basic genetics, and does in itself not really tell us a lot. However, by comparing these sequences to those of other animals, we are able to learn how different species are related to each other. In addition, we can find familiar genes that will tell us something about the animal or organism whose genome was sequenced.
For example, let’s say we sequenced the genome of a plant. We find a familiar sequence that we know code for production of a toxin protein, and this knowledge let us know that it most likely produces this toxin itself, possible to avoid being grazed upon. It’s obviously something that takes a long time to figure out in real-life conditions, but this is the basic behind it. No really the best example, but the point I'm trying to make is that we really need to know what to look for in the huge string of base-pairs that we get from the genome sequence.
Just a decade age, a genome sequencing would take a very long time and cost insane amounts of money, but the genetic discovery technology has rapidly improved lately, and these days we are not too far away from getting genome sequence to receive personalized medicine. Anyway, that's a topic for another post.
The sequence can be done from a single animal cell if we have enough DNA in it, and this is what happened for the Tasmanian Tiger; a 108-year-old pouch young was preserved, and gave good results!
What did the genome sequence tell us about the Tasmanian Tiger?
The first thing that the researchers who sequenced the genome was able to tell us is that the its placement in the evolutionary tree is indeed correct, and thus confirming its place as being part of a sister lineage to the Dasyuridae family - a family that includes quolls and Tasmanian devils. Not really big news, but getting genetic confirmation for an established theory is actually pretty nice for the scientists who study these animals.
Image is Public Domain.
The sequence also confirms what most people had already accepted as fact; that they are in no way related to the red foxes (Vulpes vulpes) despite their skull being almost exactly alike. This is instead a good example of convergent evolution where two unrelated species evolve into filling the exact same ecological niche.
The Tasmanian tiger on a genetic decline
One of the biggest discoveries with the sequensation of the genome of the Tasmanian tiger is that is was in a genetic decline. While scientists have believed this for a while, this new research also shows that the genetic decline probably began before the Tasmanian population got separated from the Australian one. This means that the genetic decline is more than 14,000 years old.
While a genetic decline is not an immediate threat, it shows us that the long-term sustainability of the species is not as good as it should be. What is means is that there are simply too few genes, and the different animals are not that much genetically different from each other. Once there is a genetic decline in a somewhat small population, getting it back up is very difficult, since mutation rates tend to be very slow, and a single environmental change could wipe out the entire population due to its small gene pool.
A Tasmanian tiger in Hobart Zoo in 1933. Image is Public Domain.
This means that humans might not be entirely responsible for the fact that it went extinct, and that it might have eventually got there anyway. However, we obviously did not help them surviving when we killed all of them, and if we had applied conservation efforts instead we could have potentially helped them out with the genetic problem instead.
Will we clone a Tasmanian tiger to get them back?
A complete genome sequence is the first step to take if we want to clone a Tasmanian tiger, but it is still far from possible. Right now no one is really attempted to clone a Tasmanian tiger back to life, but I could easily see that some conservation groups might want to try this at one point.
Thanks for reading
Sequencing the genome of the Tasmanian tiger could potentially reveal a lot of cool stuff about the animal, but at this point it is like a big puzzle where all the pieces are still scattered all around. I for one love the whole myth about the Tasmanian tiger allegedly being extant and hiding out in the Tasmanian wilderness, but sadly it seems extremely unlikely at this point. But it is always cool to learn more about this cool animal that used to be found in big parts of Australia. Anyway, thanks a lot for checking out the post!
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