Take the cover off some outlets and have a peek. If the paneling was added later you might even find that the outlet box isn’t flush with the paneling.
Not all wood paneling is dark. We put up light paneling in our basement on 1x2 studs (no glue) when I was a kid.
I associate knotty pine walls and such with the post-war style. Real boards, not paneling. 4x8 stuff came much later.
The only panels we kept were on one wall in the lounge, above the fireplace. They were real wood, with a deep grain pattern, but were a horrible grey colour. I painted them in a matt off white colour and now they look more like board-marked concrete, with a texture that gets picked up when the evening sun falls across it. What was a pretty naff 1970s feature looks (IMHO) pretty good now.
Orange pine can get knotted, though (pun intended).
Considering you might compound the problem I agree with painting. I used to have a second home that we painted over dark (ugly) paneling with a light pastel color. It came out great and you didn’t really notice it was still paneling.
Our house has a lot of wood paneling. It’s ship-lath, attached to the studs.
My step-sister and brother in law had a massive mansion which was built about 1890; it had wood panelling. Sometime around the 1950’s, someone decided that rather than refinishing the old tired wood, they should paint it - bathroom green. (Seriously - that institutional light green that we associate with bathrooms) That was in 2000 square feet of downstairs panelling and ceiling beams, and would have been a nightmare to strip if they wanted wood finish. OTOH, BIL bought it for $150,000 and it was sold for almost $3M after living there for 40 years or so - putting up with the colour was worth it.
If the panelling was put up at the same time- odds are there is nothing but stud behind it. Why would a builder go through the trouble of finishing a wall just to cover it up? IMHO at the time prefinished wood sheets and strips of moulding at the gap would have been classier and faster (not cheaper) than sheetrock, and certainly simpler that lathe and plaster if it’s that old. Back long ago, wood would not have been so much more expensive.
Painting wood paneling, especially the cheap fake stuff, is possible, but I wouldn’t say it looks good, as others have said above.
The previous owners of our house decided that finishing the basement would be easier with the cheap wood paneling. Not real boards, but the 4’x8’ stuff. And then they decided to paint it. And it looks like paint over cheap paneling. The grooves show through. The lines between the boards show if you know where to look, because you can’t exactly use mud and tape if you want paneling. I’m pondering using drywall mud and tape, and filling in the grooves, so I can have flat walls. Either that, or rip it down and put up sheet rock. Sheet rock is cheap.
Sheet Rock is cheap but taping is a hard job usually.
When someone says “paneling,” I can think of two kinds with vastly different characteristics. The oldest kind is real wood, supplied as either random or regular widths, with a tongue & groove installation. This kind is thick and strong enough that no backing is needed, just nail to the studs, sometimes at a angle for more strength. A finish of stain and varnish is typically added. I have several walls like this in my present house, and it looks very rustic.
The other kind of paneling that I have seen or used comes in 4x8 sheets, basically a veneer with very little structural strength. It could be installed direct to studs, but that’s not a good way. First drywall (a finish coat isn’t needed), then attach the 4x8’s to that, making a strong composite wall. If you wanted to repanel, you would probably have to remove both drywall and veneer, down to the studs, and start over.
I put up a lovely looking, Norwegian veneer paneling on three sides of a room in a house I had not long ago. It was certainly not cheap wallpaper-type image, but real wood, and quite expensive. It looked quite luxurious, especially if you like the Scandinavian motif.
More wood paneling and behind that still more. It’s wood paneling all the way down. 
Seriously though, it could be lots of stuff. Pop it off and see is all you can do.
How old is “older”? If the house was build before 1920, it has lath and plaster walls. Removing the wood panel will destroy the plaster, and then you will find that the stubs aren’t even, so you have to build them up to be able to hang wall board.
I hate painted wood - really, really hate painted wood - but that is the best solution. The wood will have to be scrubbed, lightly sanded, and then wiped down with alcohol to prep it for painting. You might find after doing all that, that the wood is much lighter. If it is, well painted wood looks fine.
Maybe a bootlegger owned that house in the past and papered the walls with 100 dollar bills underneath the paneling. Yep, I would look. It could happen.
As a fan of Fixer Upper I know it’s not, but all of the paneling I’m seeing is. I could cope if it looked like this. But it doesn’t. It looks like this and this and lots of this and this.
I am searching allover the internet for a particular woodgrained look wrapping paper. 90% of the clicks get me to sites with contact paper in their product lists. Whoever thought there were so many colors of contact paper? And some of these people are using it in weird ways. I mean, isnt contact paper for shelf and drawer lining? It’s not wall covering, right?
This is what we have. And funnily, throughout the house the timber has been set horizontally on all the walls except for one room (second living room) where it is on the diagonal.
I love it, except for the lack of light on particularly miserable days.
My paneling was glued over drywall. Only one wall thankfully. The panels peeled off easy but the black glue material remained. Many hours of power sanding…
But after painting, you could not tell it from the other walls. The wall had been painted several times before the panels were glued up. That made sanding a bit easier as there was not bare drywall paper to damage and a thicker base of paint to protect it. But I still had to use a finer grit to not gouge it up.
We had paneling in our late 50’s/early 60’s house when we bought it 15 years ago. (Plus, shag carpeting over the hardwood floors). The paneling was in a family room and we just painted it a light color. It was good enough until the room flooded during Sandy. When I went to remove the paneling what did I find? More paneling.
She musta been quite a gal.
mmm
We bought a house with some painted paneling that was…not a good color, and we didn’t care for the general look of it. So we hired a guy to fill in the grooves of the paneling with some kind of compound before painting, kinda like spackle, and then he sanded and repainted it in a better color. It’s barely noticeable now, and would probably be even less so if he had put on a primer coat first, because I think the only reason the lines are still even minimally visible is that the absorption characteristics of that compound are slightly different from the rest of the wall. Anyway, worth considering; I’d wager that even filling the grooves, priming, and painting would be way less of a headache than pulling down the paneling.
Spackling and sanding are not that difficult, a lot easier than mudding and taping drywall, which requires a lot of special tools and a lot of skill.
Another poster chiming in with PAINT IT! You can spackle the grooves and make it smooth and then paint it.
We had wood paneling in our living room growing up. My mom wanted it replaced and sure enough there was plaster and lathe (and horsehair) underneath the firring (sp?) strips. So removal (of the first wall) was no problem, but the problem was that all of the trim (around doors, floorboards, corners) was now > 1" out from the wall and even the carpet and hardwood floors would be messed up. So we ended up making new firring strips and building sheet rock out to the same depth of the orginal wood paneling. So thankfully only 1 wall went through this ordeal.
To be fair, the sheet rock wall did look better but the time and expense was 10x more than the improved look.