To help speed breeding you can create spontaneous conception AND birth!
Just drag a female breeder onto a male and as soon as you see "going indoors", just tap on "detail" and check if she is nursing. If so, just drag her on the screen and POP!, she's holding a baby! If you don't get the "going indoors" message or she isn't nursing when you check, just keep dragging her to other males or even back to the same one until you do. Even if the males run away I just keep dragging them back and dragging the breeder to them. It's kinda weird to create such a forced breeding program. I keep thinking to myself "get back there and make a baby NOW!"

Also, if the breeder is weakened you won't get the nursing message but you can just move her after the going indoors message and see if a baby pops up immediately.

I do something similar where as soon as the happy couple *kiss* I toggle to the MAP screen and see if my population has increased, and if not I grab the couple and get them kissing again!
It's funny that I've paired a young woman with an "Elderly" man, and the woman has come out with a baby in her arms before her beau even gets to the hut!!

Since "going indoors" is just for show, you can check immediately after the kiss to see if she is nursing. I do this often to save the time.

For fun, I grabbed one of my ladies and started plunking her on top of one guy after another to make them kiss until finally she won't kiss and the baby appears. In the meantime, all of her beaux are marching into the hut at once while she's long gone with her new bundle of joy...lol.

I have found that breeding stops when you reach a certain level. Nobody wants to conceive. Now that they have spirituality, it's, "I have a headache tonight". My breeders have died off and I'm now desperately trying to get enough tech points to buy more fertility.
Gail

Your tech levels are not what's limiting your breeding efforts, although breeding gets easier with higher levels of fertility. There are several reasons that villagers aren't interested in breeding: not enough housing, they don't "hit it off" with the mate you've chosen, or one or both of the villagers is too young.

You will experience a housing shortage four times in the game. The first three times can be resolved when your villagers build a new hut. The last time, however, indicates that you've reached your village's maximum population, since there are no more huts to build.

Hi Barbara,
I have enough huts (2 extra unused) and have put all my 9 people on "Breeding". Nobody is interested. Any other assistance? I hate to think that I will just watch these people grow older and die. Oh yes, they also have plenty of food and water.
Gail

Watch for a message when you try to breed. If it says "There isn't enough housing" then your villagers need to build a new hut. Not all of the huts on Isola can be used by your villagers for housing, and they need to build new huts periodically to enable them to expand!

Barbara,
LOL! I finally got a man a bit "adept". He was then waiting for someone. He went indoors into one hut, the woman went into another hut and came out carrying a baby! No, there was nobody who left before or after she did. I guess "size" does matter.
Gail

That's one of many interesting effects of how breeding in the game works. I won't go into all the technical details, which would spoil the mystique! It does create a lot of hilarious forum conversation!