Everyone who travels talks about how hard it is to hang up their travel boots, and if the infamous 'travel bug' were an actual illness then GPs around the world would be inundated with patients.
Travellers are constantly in the search for the unknown, to get lost in new and exciting locations, to get off the beaten track. Each adventure becomes more far-flung, more extreme, and dare I say it, more dangerous.
There's no doubt about it, travelling is on our blood. But what exactly does that mean? And why do we travel?
One scientist, Svante Pääbo, is on a quest to sequence the Neanderthal genome, and he has come up with a theory as to why humans travel and seek the unknown.
Pääbo said: "I want to know what changed in fully modern humans compared with Neanderthals. What made it possible for us to build up these enormous societies and spread around the globe."
Records show that Neanderthals evolved in Europe or Western Asia and roamed the globe from there, only stopping when they reached water or some other obstacle. However, this is where modern humans differ; modern humans carry on. They don't stop. They continue to travel despite the obstacles, overcoming anything and everything put in front of them.
If the defining characteristic of modern humans is a hunger and desire for the unknown, then there must be a gene for this.
Pääbo continues: "It's only modern humans who start this thing of venturing out on the ocean where you don't see land. Part of that is technology, of course; you have to have ships to do it. But there is also, I like to think or say, some madness there. You know?
"How many people must have sailed out and vanished on the Pacific before you found Easter Island? I mean, it's ridiculous. And why do you do that? Is it for the glory? For immortality? For curiosity? And now we go to Mars. We never stop.
"We are crazy in some way. What drives it? That I would really like to understand. That would be really, really cool to know."
As travellers, we are crazy in some way. We throw ourselves out of planes at 15,000 ft, down grade 4 river rapids, and across canyons on elasticated pieces of rope. We're always putting ourselves in situations that are deemed 'dangerous', and do you know what, we love it, we come out the other end grinning from ear to ear.
Yes, we are crazy in some way; that's why we travel...