What if your pet could help cure cancer?

A photogenic green-eyed Russian Blue named Petra might just be the world’s most genetically-sequenced cat. Petra was rescued from an animal shelter in Reno, Nevada, by Charlie Lieu, cofounder of Darwin’s Ark, a community science nonprofit focused on pet genetics. Since becoming Lieu’s furry friend, Petra has had her DNA fully sequenced six times and extracted nearly 60 times, all in the name of science.

(Lest this conjure images of Petra being held as a tortured test subject in some kind of lab full of mad scientists, please note that “DNA extraction” in Petra’s case looks like… getting brushed. More on this later.)

Petra is just one of more than 67,000 cats and dogs whose information has been entered by their human caretakers into Darwin’s Ark databases, which the organization’s researchers and collaborators are using to try to better understand pet health and behavior. Since its founding in 2018, Darwin’s Ark has helped researchers probe everything from cancer to sociability to whether or not trainability is inherited, allowing them to debunk stereotypes about dog breeds and investigate similarities between complex diseases in humans and animals.

DNA testing for dogs is common at this point, with multiple for-profit companies offering to break down your pet’s breed background for a fee. But Lieu and her Darwin’s Ark cofounder, Elinor K. Karlsson, wanted to go beyond offering individualized DNA reports and invite humans to participate in surveys about how their pets play and socialize, and even whether or not they get the zoomies right after using the litter box. This approach pairs DNA with vast amounts of behavioral data collected by the people who know these animals best, thus harnessing the power of humans’ love for their pets to advance cutting-­edge science.

In the process, Darwin’s Ark has solved a problem that is often an obstacle in human medicine: how to get the enormous quantity of data needed to actually understand, and eventually solve, medical problems.

It was this problem that initially interested Lieu, who is chief of research operations for Darwin’s Ark, in pet genetics. Lieu spent some of the early, formative years of her career working on the Human Genome Project at the MIT Center for Genome Research, where she first collaborated with Karlsson. She remembers sleeping under her desk in the late ’90s “babysitting” servers in case they needed to be rebooted in the middle of the night. For many years, her North Star was cancer research: Her mom had died of cancer, “nearly everyone” on her mom’s side of the family got cancer at some point, and Lieu herself had her first of multiple tumors removed at age 17.

Throughout her nearly 30 years working with the Broad and other initiatives related to such research, Lieu has often felt struck by how difficult it is to study complex diseases like cancer. Gathering extensive data about people while maintaining their legally mandated privacy can be tricky, as is getting them to participate in strict protocols over the course of many years (an issue she has also experienced from the other side, since she is enrolled in multiple longitudinal studies).

About a decade ago, Lieu reconnected with Karlsson. Karlsson bemoaned how hard it was to get the large-scale genomic data needed to advance scientific understanding, and something clicked. What if they could collect genomic data from pets as a proxy for understanding complex diseases and behavior? “We talked a lot about how we [might] enable a platform that could help us collect the right kinds of data at the level that’s necessary in order to do the kinds of science that the world needs,” Lieu says. That might be hard with humans, but “everybody wants to talk about their dogs and cats, right?”

Thus Darwin’s Ark was born. Initially it focused on dogs, and using its data, Karlsson and a team from the Broad and elsewhere were able to demonstrate that just 9% of variations in behavior can be predicted by breed—much less than people might think. Lieu hopes the finding will help certain much-­maligned breeds such as pit bulls, which tend to be adopted at lower rates and sometimes are even put down on the basis of faulty assumptions about their behavior.

But the work Darwin’s Ark is doing isn’t just helping pets—it could benefit humans, too, as researchers increasingly probe the links between human and animal cancers.

“We were involved in some early dog work in cancer, where we collaborated with another group to understand whether or not you could take a blood draw and figure out whether or not the animal has cancer,” says Lieu. “Turns out you could. And in the last couple of years, an FDA-approved test has been available for humans to figure out whether or not you have lung cancer. All that work started in dogs, so you could start to see the power of doing something in animals that then impacts human health.”

I wrote about Darwin’s Ark as part of a profile on Charlie Lieu for MIT. The profile is wide-ranging as it tries to capture even a little part of the story of Lieu’s long and storied career, but the Darwin’s Ark bit is what I keep coming back to. Beyond providing insight into both human and pet health, the methods that Darwin’s Ark has developed for gathering DNA could have significant implications in conservation, too.

Gathering DNA from endangered or sensitive animals via blood or skin samples can be prohibitively difficult or distressing to the animals. But, inspired by domestic cats, who are not very amenable to having a swab stuck in their cheek for DNA collection, scientists at Darwin’s Ark figured out how to extract DNA from fur or hair that has been shed, not plucked — which could be great news for scientists trying to track wild animals of all kinds who need a lighter-touch approach to DNA gathering.