There are no cold-blooded mammal species left alive in the world, and apparently that's our fault.
In essence, you can split every animal in the world down to either an endotherm or an ectotherm.
Warm-blooded creatures such as mammals and birds are endotherms, which mean we're able to maintain our own body temperature without an external heat source.
Of course, if you lived on a planet without a heat source like our sun, then you'd freeze to death, but in general mammals and birds are warm-blooded and can maintain their own heat.
The other group consists of creatures such as reptiles, amphibians, insects arachnids and fish and they're ectotherms, which means they need another source of heat to keep warm.
It wasn't always like this though, as according to a study from Romain David and his team, mammals shifted from being cold-blooded to warm-blooded over time.
However, there was one holdout which lasted for a very long time until it came into contact with nature's perfect killing machine - humans.
This species was a type of cold-blooded goat called Myotragus balearicus which used to live on the Spanish island of Mallorca before either of those names existed.
Remains of these animals found that they were about 45cm tall, with very stubby legs and a bone structure more akin to reptiles.
Living on an island with very little in the way of threat for this cold-hearted goat meant they became complacent and didn't have to spend their time fighting for food or learning to survive.
Making their home in one isolated location with pretty much no natural predators is pretty much a recipe for disaster when humans show up, because we will invade and kill wherever we can.
The species has nowhere to go and lacks the means and instincts for avoiding us, so people pretty much hunt the poor animals to extinction.
When humans first arrived in the Balearic Islands in around the third millennium BC it was pretty much game over for Myotragus balearicus.
Experts have debated whether it was environmental factors or good old human beings who were responsible, but the dominant theory is that we're responsible for the extinction of the last cold-blooded mammal species in the world.
It is believed that this species of cold-blooded goat which had lived for millennia didn't survive another 100 years after they came into contact with us.
Humanity remains undefeated, except of course by itself and emus but you've got to admit those birds are damn tough.Featured Image Credit: Wikimedia Commons/PHAS/Universal Images Group via Getty Images