Getting no aliens in free play

[Woo]

I don't know what I'm doing wrong, but I'm having a hard time finding a freeplay map that actually gives me an acceptable amount of aliens.
I'm starting my games as I usually do with all kind of strategy/building games - I open a new map, lay down a minimal home base (here: 1 burner miner for coal and 1 for iron, and a furnace for iron plates), and while those are producing some "starting capital", I go scout the rest of the map.
This, as of yet, does not seem to work in Factorio. I'm on the 20th map now, and I find *no* aliens *at all*. Nowhere.
Since I'd like to keep the fighting challenge low, I started with trying "few enemy bases, small, high richness", on a map of 1000x1000, assuming it would give me exactly that - one or two clumps of alien nests of an easily conquerable size.
I got: none. For 5 random maps.
I turned up the difficulty to "normal amount of enemy bases, normal size, high richness", same 1000x1000 map size..
I got: none. For another 5 random maps.
I tried several other combinations of frequency, size and richness.
I got: none. For another 8 random maps.
I thought, ok, it's still kinda beta, perhaps the map generator is a bit wonky.. let's go to the extreme.. "very high enemy base frequency, very big, very rich".
I got what I asked for. Basically, the whole map around my starting point was RED. I couldn't walk half a minute in any direction without standing in a swamp of aliens.
Of course, one shot at any of those creatures meant instant death for me. So that wasn't going to work either.

I even played a few of the "no aliens" maps to about halfway through (until all the red-only based research was finished), hoping that some aliens might spawn a bit later,
but as I now assume from observation, once the map tiles are generated, you're stuck with them, and if there are no alien bases from the beginning, there won't be any spawning later.

So, like I asked at the beginning - what am I doing wrong? Does the game really know no gradients between "no aliens" and "everything full of aliens", or are my settings so unusual that I keep messing it up myself without knowing?
How can I tweak the map settings to get something that fits my style? (I would prefer to go without mods and lua commands, since I still have a few achievements to get...)

[DaveMcW]

"Starting area = Medium" gives you a 1000x1000 safe zone with no aliens. Reduce the starting area, or make the map bigger.

The default setting of infinite map size usually works fine, it won't actually generate most of the map until you explore or pollute it.

[Woo]

Thanks a lot, that explains my experiences.. I've usually left all other parameters on default, which means I seem to have had my whole map as safe zone.. *facepaw*

[Deadly-Bagel]

Is it just me or is there a disproportionate number of furries on this forum? xD