Why do baby teeth come in in the order they do?

October 5, 2009 3:58 PM

Why do baby teeth come in in the order they do?

Since babies don't start out eating carrots or other particularly hard foods, but do need to mash softer foods, it seems like it would be more advantageous for the molars to come in first. Also, it would cause less discomfort to the mother during breast feeding. So why does it start with the incisors and end with the molars?

posted by Bugbread to health & fitness (13 comments total)

Either it's a defense thing (all the better to bite you with, my dear), or it's a great big meh from an evolution standpoint.
posted by Sys Rq at 4:07 PM on October 5

The logical reason, which I've seen mentioned in a biology textbook somewhere, is that development the other way around would lead to the central incisors being crammed together & displaced.
posted by Pinback at 4:17 PM on October 5

Oddly enough one of the common changes that happens due to Trisomy 21 (Down syndrome) is that teeth come in late and in unusual order.
posted by plinth at 5:20 PM on October 5

They mash with their gums, not teeth. My 11-month-old can handle a lot of foods, but only has his 2 bottom teeth.
posted by k8t at 5:24 PM on October 5

Teeth don't bother a nursing mother at all.
They'll only nip you once, if that.
posted by SLC Mom at 5:42 PM on October 5 [2 favorites]

Baby gums are awesome for chewing, teeth or no teeth. Babies are terrible at biting off pieces of things, so I wonder if they get their biting teeth first so they can start practicing that skill, and by the time they have the molars necessary to do heavier duty, they're less likely to literally bite off more than they can chew.

I would make the case that baby teeth are not responsible for the majority of breastfeeding discomfort; I think most women tend to find the process most difficult at the very beginning when teeth aren't in play.
posted by padraigin at 5:47 PM on October 5

Imagine you are placing a piece of sticky tape onto a piece of paper. If you place the two ends first and then flatten towards the middle, the middle will be wrinkled and bunched. If, on the other hand, you lay the middle first and then flatten out towards the two ends, the tape will go down smoothly.

This is essentially what Pinback said.
posted by alms at 5:58 PM on October 5 [1 favorite]

Pinback, thanks, that makes sense.

Teeth don't bother a nursing mother at all.
They'll only nip you once, if that.

My wife would beg to disagree.
posted by Bugbread at 6:11 PM on October 5

I'm not quite buying the other-way-around-would-make-them-crowded thing; when they fall out, in their place grow bigger teeth that are very often crammed in all higgledy-piggledy.

Furthermore, the teeth don't just pop out of nowhere. All your teeth--including your permanent teeth--begin to develop in the womb. The parking spaces are pre-assigned.
posted by Sys Rq at 6:19 PM on October 5

Teeth aren't just for chewing. Tooth development helps jaw and muscle development. It also helps in forming language. Evolutionary advantages, all.
posted by Cool Papa Bell at 6:26 PM on October 5

This may be a bug in humans and a feature in some of our evolutionary ancestors. Perhaps some of them experienced some advantage from early incisor development and it's just a random holdover in humans.
posted by twistofrhyme at 11:45 PM on October 5

Many of these answers include some of the reasons teeth erupt in the order that they do. teeth are formed as buds: islands of specialized cells inside the jaw bones. the order is basically genetically programmed, and independent of chronological age.
Small teeth, like incisors, form more quickly, and begin to erupt when the crowns are complete, pushed through the gums as the roots form. molars follow when they are developed and enough jaw growth has occurred to accommodate them.
posted by OHenryPacey at 11:46 PM on October 5

Teeth don't bother a nursing mother at all.
They'll only nip you once, if that.

Not to derail, but Bwah-ha-ha-ha ha. I have scars.
posted by not that girl at 12:52 PM on October 6