Thanks to Fabiana and Hazel for their suggestions this week, where we learn more about dogs and cats!

Further reading:

Gene mutation that makes dogs small existed in ancient wolves

Feline genetics help pinpoint first-ever domestication of cats

Cats Learn Names of Their Feline Friends

A cat (Dracula, specifically, with Dracula the toy):



A dog, in case you've never seen a dog before:



Show transcript:
Welcome to Strange Animals Podcast. I’m your host, Kate Shaw.
This week we’re going to revisit two great topics suggested by two great listeners, Fabiana and Hazel. They suggested dogs and cats, respectively. We’ve covered both before, but there’s always more to learn about any animal. Let’s look specifically at two recent studies that can add to our knowledge.
We’ll start with Fabiana’s suggestion of dogs. Results of a study published in January of 2022 examined the genetics of wolves and dogs to see how small dog breeds developed. We’re not completely sure how domestic dogs are related to wolf species alive today, since dogs have been domesticated for tens of thousands of years, and were probably domesticated at different times in different places by different groups of people, and potentially domesticated from different species of wolf, and since wolves and dogs can interbreed and produce fertile offspring. It’s very complicated, to say the least.
Wolves are roughly the same size throughout the world, depending on species and environment. The gray wolf, which is native to the northern parts of North America and most of Eurasia, stands about 2 and a half feet tall at the shoulder, or about 85 cm, and weighs around 88 lbs, or 40 kg, on average, although wolves who live in warmer areas tend to be smaller. There are certainly dog breeds bigger than this, but there are lots of dog breeds that are much, much smaller. I mean, the Chihuahua only grows around 9 inches tall, or 23 cm, and usually barely weighs 6 lbs, or 2.7 kg.
The prevailing belief is that small dog breeds came about because people bred the smallest dogs together and chose the smallest puppies from that pairing to breed to other small dogs. That’s true, but the genetic capacity for small size had to be there to start with in order to breed a 6-lb Chihuahua from an 88-lb wolf, no matter how many generations of dogs were in between. Researchers knew the genetic code for this size difference had to be somewhere, but it took a decade of study before they found it.
Once they found the growth hormone mutation that could allow for very small size when expressed, they searched for it in over 200 dog breeds to see if it was there in all dogs. Sure enough, it was. The scientists hypothesized that the genetic mutation showed up after dogs were domesticated, somewhere around 20,000 years ago. To test this, they looked for the mutation in the genetic profiles of both living and extinct canid species.
To their surprise, the mutation was present in all of them, including the genetic profile of a Siberian wolf that lived 54,000 years ago. Without this mutation, we wouldn’t have Chihuahuas or Yorkshire terriers or other small dog breeds that so many people love. That means the mutation was beneficial for domesticated dogs, but at the same time it was mostly non-beneficial for wild canids.
When dogs were domesticated around 20,000 years ago, and possibly well before that, the world was in the middle of a glacial maximum. The climate throughout the entire Earth was considerably colder than it is today. Ocean levels were lower because so much water was frozen, with ice sheets covering northern Europe and North America to a depth of about 2 1/2 miles, or 4 km. Northern Asia had fewer ice sheets but was much dryer than it is today. In fact, the world was a lot dryer overall, so places that weren’t covered in ice were more likely to be deserts, leading to massive dust storms and just a general dustiness throughout the world.