Whose ears popped first?

Free diving for food probably.

The first person to fall off a high cliff? (Not sure if free-falling is considered a "transportation technology"....)

The modern diving-bell was invented by http://en.wikipedia.org/wiki/John_Smeaton in 1788, and the first references to ear-popping occur fairly soon after that. The Russian physician Joseph Hamel (Iosif Gamel, 1788-1861) mentions it in his paper 'On the Diving-Bell as a Means for Curing Deafness', 1816 (pdf available http://www.tandfonline.com/doi/abs/10.1080/14786441608637600, free text on http://books.google.co.uk/books?id=wHM6AQAAMAAJ&pg=PA22&lpg=PA22&dq=hamel+%22on+the+diving+bell%22&source=bl&ots=3jfqSaIcev&sig=xvUK0HGLymb62zfXNvXZoKjYQRI&hl=en&sa=X&ei=2ZiEVJboEov6UJyhgfgP&ved=0CBYQ6AEwAQ#v=onepage&q=hamel%20%22on%20the%20diving%20bell%22&f=false). The sensation was so new to Hamel that he didn't realise he could relieve the ear-popping simply by swallowing: When I was in the diving-bell, and made my exertions to admit air into the Eustachian tube, I was not aware of the simple way in which it is effected. http://en.wikipedia.org/wiki/William_Hyde_Wollaston informed me, that nothing is wanted but to swallow the saliva .. To admit the air into the ear, one must merely swallow saliva, and at one of these exertions the air will rush in, if the obstruction be not very considerable. Of course the phenomenon had been known in some form since antiquity. Aristotle says that divers put olive oil in their ears, or tied sponges round them, to try and stop their eardrums bursting. (He also describes the slight ear-popping caused by yawning.) The science to explain it had been around since the sixteenth and seventeenth centuries, when http://en.wikipedia.org/wiki/Bartolomeo_Eustachi described the Eustachian tube and http://en.wikipedia.org/wiki/Blaise_Pascal showed that barometric pressure was affected by altitude. But ear-popping as such doesn't seem to have been properly described till the nineteenth century. Hamel wasn't even sure if other people experienced it too: I was anxious to know whether men that had been in diving-bells before, had noticed the same sensations as myself, and I made them describe to me what they had felt. Among other things they stated, that when at a great depth it had been to them "as if a shot was fired through their brain." This was evidently the rushing in of the air through the Eustachian tube.

You don't have to dive very deep to make your ears pop, either.

Humans have very similar ears to other mammals. It is the opening and closing of the Eustachian tube that causes the popping sensation, and that is in response to pressure changes. Pressure does not just change from altitude -- air pressure changes as the weather changes. I have had my ears pop during a rapid change from high to low air pressure during a storm, for example. This is an interesting Wiki on the http://en.wikipedia.org/wiki/Evolution_of_mammalian_auditory_ossicles#Mammal-like_jaws_and_ears. I imagine that ear popping - or a similar sensation - has occurred in mammals before humans came along, as a response to changes in external or internal pressure.

It doesn't even take a head cold. Just really lousy sinuses, which I'm sure someone in our ancient past had to have suffered from. My sinuses constantly drain and, as a result, I'm constantly popping my ears.

Sliding down a snowfield.

Sliding down a snowfield. I'm not sure my ears have ever popped while skiing. Which is odd, because it's an entire day of going up and down 1500 feet (at my local ski hill). Major city dwellers, does an 80+ story elevator do it? Not a Major City Dweller, but yes. I know for a fact that both the Space Needle (~500 feet) and the 60th floor of the Chase building in downtown Houston (~800 feet) both caused my ears to pop.

My ears pop nearly every time I ride a train through the tunnel under the Hudson River...