If we make a taxonomic sandwich between a Equus quagga ... Back in episode 1, we defined a species as a group of all the animals of the same type that can breed together over multiple generations.

Perhaps most strangely of all, given the ... their own species of wild horse, the zebra? Zebra are closely related to the domesticated horse, sharing a genus (Equus) and a common ancestor.

So much so that they may be Earth's next big species if ours ends up going the way of the dinosaurs. While an octopus-dominated future may seem "improbable" at the moment, it "wouldn’t be the ...

They cover less than 1% of the planet’s total surface, yet they’re home to almost a quarter of all vertebrate species – including over half of all the world’s fish species. It’s an extraordinary fact: ...