Researchers map 100-year-old brains of extinct Tasmanian tigers

Brains of long-dead animals can still offer scientific insights.

While much is known about the brains of humans, mice, and monkeys, other animals remain relatively understudied, hindering our understanding of how brains evolve and adapt to new environments. New research with Tasmanian tigers’ brains shows that current neuroimaging techniques can examine not only living animals’ brains, but also those that are long extinct, to fill that gap. We speak with Emory University neuroscientist Gregory Berns to learn more.

ResearchGate: What are Tasmanian tigers?

Gregory Berns: Also known as the thylacine, the Tassie tiger was the apex predator in Tasmania until it was hunted to extinction. The last known thylacine died in the Hobart Zoo in 1936. Although they are marsupials, the looked very canid-like. They were striped – hence the name. Thylacines’ behavior was never studied scientifically. What we know about it comes from observation of zoo animals, whose behavior is not indicative of wild animals, and from stories from bushmen and trappers.

A Tasmanian tiger at Hobart Zoo in 1928. Credit: Benjamin A. Sheppard

RG: Why did you want to map their brains?

Berns: For the last five years, I have been working to map the dog brain by training dogs to go in an MRI completely awake and unrestrained. To date, we have scanned more than 80 dogs on a variety of tasks to understand how they see and hear the world, what’s important to them, and how they have self-control. When I learned about the thylacine, I became fascinated by their outward resemblance to dogs and wanted to know if their brains were wired similarly. That began a two-year quest to find any existing thylacine brains.

RG: Where did the samples you studied come from?

Berns: One thylacine brain is in the Smithsonian Institution, and the other is in the Australian Museum in Sydney. For comparison, we also studied the brains of two Tasmanian devils. One came from the Smithsonian, the other came from a recently deceased devil in the Save the Tasmanian Devil Project.

RG: How were you able to map these brains?

Berns: We used an MRI technique called diffusion tensor imaging (DTI), which maps the white matter pathways in the brain. White matter contains the connections between neurons, so mapping these gives us a roadmap to how brains are wired. When we compare these wiring maps between species we obtain new insights into the relative importance of different sensory systems, or, in the case of the thylacine, the size of its frontal lobe, which may be related to its cognitive capacity or intelligence.

RG: What did you find?

Mapped thylacine brain. Credit: Emory University

Berns: Despite the external resemblance to dogs, thylacines’ brains are very different. Thylacines were marsupials, and you have to go back almost 150 million years to find the common ancestor between marsupials and placental mammals, which dogs are. For example, marsupial brains have a different set of pathways to connect the left and right sides of the brain. We also found that the thylacine had a relatively larger frontal lobe than the devil, which suggests that it was more cognitively complex. This is likely because it was a predator and had to hunt its prey, whereas devils can scavenge.

RG: Could other extinct animals’ brains be mapped?

Berns: Yes, if their brains are well preserved. We have launched an effort to do this in the Earth’s remaining megafauna before they go extinct.

RG: What could that tell us?

Berns: We currently know very little about how brains evolved. We know a lot about the brains of humans, rats, mice, and monkeys, but there are a lot of other animals out there. For example, what in a dog’s brain makes him a dog and not a cat or a bear? Studying the structure of other animals either those still living or those already extinct may help us understand how animals adapt to their environment, and help those who can’t adapt to changing global conditions.

Featured image courtesy of Emory University.