# Two teats or four? **URL:** \ **Category:** Factual Questions\ **Created:** [November 20, 2011, 7:06am UTC](https://boards.straightdope.com/t/two-teats-or-four/603532 "2011-11-20T07:06:59Z")\ **Posts on this page:** 12\ **Page:** 1
**Author:** ![Patch](https://avatars.discourse-cdn.com/v4/letter/p/a183cd/32.png) [@Patch](https://boards.straightdope.com/u/Patch)\ **Post date:** [November 20, 2011, 7:06am UTC](https://boards.straightdope.com/t/two-teats-or-four/603532/1 "2011-11-20T07:06:59Z")
I’ve noticed that animals such as cows, deer, and moose have udders with 4 teats. Goats and sheep have two. I don’t know the right term to use here, but is there a division in a classification of animals that includes this, so you could know if, say, an ibex mom has two teats or four? ---
**Author:** ![GaryM](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/garym/32/241_2.png) [@GaryM](https://boards.straightdope.com/u/GaryM)\ **Post date:** [November 20, 2011, 3:41pm UTC](https://boards.straightdope.com/t/two-teats-or-four/603532/2 "2011-11-20T15:41:08Z")
Just to add to confusion, don’t dogs and cats have six or eight? Probably tied to average litter size? ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [November 20, 2011, 4:21pm UTC](https://boards.straightdope.com/t/two-teats-or-four/603532/3 "2011-11-20T16:21:48Z")
> [@Patch](#): > > I’ve noticed that animals such as cows, deer, and moose have udders with 4 teats. Goats and sheep have two. I don’t know the right term to use here, but is there a division in a classification of animals that includes this, so you could know if, say, an ibex mom has two teats or four? Not really. The number of teats is fairly flexible evolutionarily. There may be certain numbers that are characteristic of particular genera, families, or even orders, but this is not generally a primary character for classification. Note that cows are much more closely related to goats and sheep (all family Bovidae) than they are to deer or moose (Cervidae). ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [November 20, 2011, 5:45pm UTC](https://boards.straightdope.com/t/two-teats-or-four/603532/4 "2011-11-20T17:45:40Z")
You’ll even occasionally get a human with more than the standard-issue two. ---
**Author:** ![yabob](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/yabob/32/2821_2.png) [@yabob](https://boards.straightdope.com/u/yabob)\ **Post date:** [November 20, 2011, 7:55pm UTC](https://boards.straightdope.com/t/two-teats-or-four/603532/5 "2011-11-20T19:55:57Z")
Sometimes it’s variable (in normal individuals, not the occasional abnormal case). Pigs may have as few as 8 or as many as 16. ---
**Author:** ![AClockworkMelon](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/aclockworkmelon/32/10803_2.png) [@AClockworkMelon](https://boards.straightdope.com/u/AClockworkMelon)\ **Post date:** [November 20, 2011, 8:08pm UTC](https://boards.straightdope.com/t/two-teats-or-four/603532/6 "2011-11-20T20:08:06Z")
> [@Chronos](#): > > You’ll even occasionally get a human with more than the standard-issue two. Has a human ever had more than two _functioning_ ones though? No really, I want to know! ---
**Author:** ![Patch](https://avatars.discourse-cdn.com/v4/letter/p/a183cd/32.png) [@Patch](https://boards.straightdope.com/u/Patch)\ **Post date:** [November 21, 2011, 4:52am UTC](https://boards.straightdope.com/t/two-teats-or-four/603532/7 "2011-11-21T04:52:56Z")
> [@GaryM](#): > > Just to add to confusion, don’t dogs and cats have six or eight? Probably tied to average litter size? I’m thinking more in terms of the bag between the hind legs, versus the variation in mammary quantities found along the body ---
**Author:** ![Smeghead](https://avatars.discourse-cdn.com/v4/letter/s/f1d935/32.png) [@Smeghead](https://boards.straightdope.com/u/Smeghead)\ **Post date:** [November 21, 2011, 12:34pm UTC](https://boards.straightdope.com/t/two-teats-or-four/603532/8 "2011-11-21T12:34:49Z")
During development, all mammals have what’s called a “milk line” that runs down the torso and abdomen - one on each side, actually. Teats can develop anywhere along those lines and in any number - from two up top, like us humans, to lots all along the lines, like dogs, cats, and pigs, or just a few down at the bottom, like cows and goats. That’s the reason why it’s evolutionarily flexible. Instead of having to develop a whole new structure in a new place, it’s more a matter of just flipping some switches along the line. ---
**Author:** ![Tim\_T-Bonham.net](https://avatars.discourse-cdn.com/v4/letter/t/46a35a/32.png) [@Tim\_T-Bonham.net](https://boards.straightdope.com/u/Tim_T-Bonham.net)\ **Post date:** [November 22, 2011, 1:32am UTC](https://boards.straightdope.com/t/two-teats-or-four/603532/9 "2011-11-22T01:32:53Z")
> [@GaryM](#): > > Probably tied to average litter size? There does seem to be some connection here. And you can see an obvious evolutionary benefit: if your average litter is 4-6 kittens, having 8 teats is an advantage. But if a human has only 1 child 99% of the time, anything more than 1 teat = 1 spare would be a waste of resources. It might be interesting to try to add to this table: ```auto Species #teats usual litter size frequency --------- -------- ---------------- -------------- human 2 1 98.92% horse 2 1 99.99% cow (beef) 4 1 98.9% - 99.6% cow (dairy) 4 1 91.1% - 98.1% cat 8 4-6 ? ``` ---
**Author:** ![excavating\_for\_a\_mind](https://avatars.discourse-cdn.com/v4/letter/e/e8c25b/32.png) [@excavating\_for\_a\_mind](https://boards.straightdope.com/u/excavating_for_a_mind)\ **Post date:** [November 22, 2011, 2:02am UTC](https://boards.straightdope.com/t/two-teats-or-four/603532/10 "2011-11-22T02:02:03Z")
> [@t-bonham@scc.net](#): > > There does seem to be some connection here. And you can see an obvious evolutionary benefit: if your average litter is 4-6 kittens, having 8 teats is an advantage. But if a human has only 1 child 99% of the time, anything more than 1 teat = 1 spare would be a waste of resources. I dunno. I’ve heard it said that anything over a mouthful is wasted, but perhaps having a spare can come in handy; there is something to be said for symmetry. If two teats reproduced more than one, I can see two as being an advantage. I’ve always liked them in pairs (although one pair is enough for me). excavating (for a mind) ---
**Author:** ![Arkcon](https://avatars.discourse-cdn.com/v4/letter/a/96bed5/32.png) [@Arkcon](https://boards.straightdope.com/u/Arkcon)\ **Post date:** [November 22, 2011, 2:10am UTC](https://boards.straightdope.com/t/two-teats-or-four/603532/11 "2011-11-22T02:10:21Z")
> [@AClockworkMelon](#): > > Has a human ever had more than two _functioning_ ones though? No really, I want to know! I’d heard of women with supernumerary nipples find them “leaking” when they’re nursing from the two, typical ones. Without stimulation, the extras stop producing milk. An outcome which is probably for the best, fetish aspect aside, because who wants to wear absorbent nursing pads up around their collarbone, or down along the bottom side of their ribcage. That’s where the human “milk line” is, the “fully developed boob on the sternum” style of the movie **Total Recall** isn’t possible. ---
**Author:** ![Tim\_T-Bonham.net](https://avatars.discourse-cdn.com/v4/letter/t/46a35a/32.png) [@Tim\_T-Bonham.net](https://boards.straightdope.com/u/Tim_T-Bonham.net)\ **Post date:** [November 22, 2011, 3:25am UTC](https://boards.straightdope.com/t/two-teats-or-four/603532/12 "2011-11-22T03:25:24Z")
> [@excavating\_for\_a\_mind](#): > > I dunno. I’ve heard it said that anything over a mouthful is wasted, but perhaps having a spare can come in handy; there is something to be said for symmetry. You are obviously male (like me). But I have been told by my sister, mother, & other female relatives that having 2 is **verrry** helpful when nursing – you switch the baby over whenever the one in use gets sore or tired or empty. And symmetry is very important to vertebrates – nearly everything in our body comes in matched pairs.