Is the Y Chromosome Endangered?

 Ever heard that frankly silly line about how the Y chromosome is somehow fragile and will eventually go away and then omg we won't have men?

It's almost certainly a myth...except there's one species of mammal in which it has happened!

The unassuming creeping vole is found throughout the western United States. They're hard to see/find because they're only about 0.67 ounces, tops.

And they have no Y chromosome. Instead, makes are XX and females are XO (which means they don't have a second sex chromosome at all.

Furthermore, the SRY gene is now on the X chromosome, and we're not sure how it's turned off in females.

The same thing is happening in Transcaucasian mole voles and three species of spiny rat from Japan. It's probably not a coincidence that they're all rodents.

So, while the human Y chromosome probably isn't going anywhere, there are species of mammal managing just fine without it!