# 98.6 **URL:** \ **Category:** Factual Questions\ **Created:** [April 2, 2009, 9:00am UTC](https://boards.straightdope.com/t/98-6/491695 "2009-04-02T09:00:36Z")\ **Posts on this page:** 11\ **Page:** 2
**Author:** ![Nametag](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/nametag/32/406_2.png) [@Nametag](https://boards.straightdope.com/u/Nametag)\ **Post date:** [April 2, 2009, 10:29pm UTC](https://boards.straightdope.com/t/98-6/491695/21 "2009-04-02T22:29:39Z")
> [@Chronos](#): > > The little sticks tell you if you _are_ pregnant, not if you’re _likely to become_ pregnant. A woman can tell when she’s ovulating based on temperature and assorted other factors (some of which are probably TMI for this thread). I assumed he was talking about [these sticks](http://www.amazon.com/Clearblue-Easy-Fertility-Monitor-30-Count/dp/B0000532PO/ref=pd_bxgy_hpc_text_b). ---
**Author:** ![SeanArenas](https://avatars.discourse-cdn.com/v4/letter/s/df705f/32.png) [@SeanArenas](https://boards.straightdope.com/u/SeanArenas)\ **Post date:** [April 2, 2009, 11:13pm UTC](https://boards.straightdope.com/t/98-6/491695/22 "2009-04-02T23:13:55Z")
> [@Nametag](#): > > I assumed he was talking about [these sticks](http://www.amazon.com/Clearblue-Easy-Fertility-Monitor-30-Count/dp/B0000532PO/ref=pd_bxgy_hpc_text_b). For a buck a day? Taking your temperature is cheaper 🙂 ---
**Author:** ![John\_DiFool](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_difool/32/19543_2.png) [@John\_DiFool](https://boards.straightdope.com/u/John_DiFool)\ **Post date:** [April 2, 2009, 11:44pm UTC](https://boards.straightdope.com/t/98-6/491695/23 "2009-04-02T23:44:45Z")
Around 97.4-.6 for me. ---
**Author:** ![ManInTheJar](https://avatars.discourse-cdn.com/v4/letter/m/ea5d25/32.png) [@ManInTheJar](https://boards.straightdope.com/u/ManInTheJar)\ **Post date:** [April 7, 2009, 5:52am UTC](https://boards.straightdope.com/t/98-6/491695/24 "2009-04-07T05:52:49Z")
I guess I should rephrase the question. What is the mechanism that keeps us all within a couple of degrees of the 98.6 degree “norm”? And why 98.6? Looking online I see a dog’s normal temp is 101, and a cat’s is 101 - 102, a horse 98.5 - 101, all within a few degrees of us. ---
**Author:** ![si\_blakely](https://avatars.discourse-cdn.com/v4/letter/s/d9b06d/32.png) [@si\_blakely](https://boards.straightdope.com/u/si_blakely)\ **Post date:** [April 7, 2009, 6:49am UTC](https://boards.straightdope.com/t/98-6/491695/25 "2009-04-07T06:49:57Z")
> [@ManInTheJar](#): > > I guess I should rephrase the question. What is the mechanism that keeps us all within a couple of degrees of the 98.6 degree “norm”? And why 98.6? Looking online I see a dog’s normal temp is 101, and a cat’s is 101 - 102, a horse 98.5 - 101, all within a few degrees of us. The [hypothalamus](http://en.wikipedia.org/wiki/Hypothalamus) regulates body temperature by influencing the thyroid (thus controlling metabolic rate) and other systems for [temperature regulation](http://en.wikipedia.org/wiki/Thermal_regulation). At the end of the day, thermal regulation is about chemical kinetics - shift the body temperature too much, and many chemical processes in the body start to fail/occur in incorrect order. We are a delicate balance of thermodynamics. A recent article in New Scientist discussed the reasons for warm-bloodedness. The traditional explanation involved speed of response to energy demands, and a wider range of ecological adaptation (at a cost of maintaining energy intake). However, newer theories involve ecological stoichiometry - the balance of chemicals in the environment. If you (as an evolutionary predecessor of warm-blooded creatures) eat plants, then to get the level of nitrogen intake you really need, you end up consuming up to five times the carbon levels you actually need. Instead of dumping that carbon, why not burn it off, stay warm and maintain energy levels. So maybe that is the evolutionary basis for warm-blooded creatures, including us. Si ---
**Author:** ![Nunavut\_Boy](https://avatars.discourse-cdn.com/v4/letter/n/e95f7d/32.png) [@Nunavut\_Boy](https://boards.straightdope.com/u/Nunavut_Boy)\ **Post date:** [April 7, 2009, 7:57am UTC](https://boards.straightdope.com/t/98-6/491695/26 "2009-04-07T07:57:29Z")
My understanding of why we live at 37C is that this is the temp at which the various chemical reactions that keep us alive happen. We have many enzymes and other proteins that work most efficiently at that temperature. Why these enzymes evolved to work at this temp I can’t say, perhaps it has to do with the stoichiometry that **si blakely** mentions. ---
**Author:** ![Philster](https://avatars.discourse-cdn.com/v4/letter/p/13edae/32.png) [@Philster](https://boards.straightdope.com/u/Philster)\ **Post date:** [April 7, 2009, 2:35pm UTC](https://boards.straightdope.com/t/98-6/491695/27 "2009-04-07T14:35:15Z")
An average is a **not** a predictor. If the average body temp is more accurately determined to be 99 by years of studies on numerous people, you can’t (and shouldn’t) expect to have your body temperature read as 99. An average of 99 means that people’s temps are reading at 98.5, 99.5, 98.4, 99.6 and so on. **They average out to 99, but that doesn’t mean you should expect 99, just something within a normal range.** It’s a lot like the dopey weather people’s forecasts. If the average high temp on April 6 in Philadelphia, PA, USA is 60 degrees and the forecast shows it will be 57, they will show this as ‘below normal’, when in fact the only thing below normal is their I.Q. **An average is NOT a predictor.** ---
**Author:** ![EmAnJ](https://avatars.discourse-cdn.com/v4/letter/e/d2c977/32.png) [@EmAnJ](https://boards.straightdope.com/u/EmAnJ)\ **Post date:** [April 7, 2009, 2:55pm UTC](https://boards.straightdope.com/t/98-6/491695/28 "2009-04-07T14:55:24Z")
> [@Labrador\_Deceiver](#): > > I’m guessing you have your reasons, but aren’t the little sticks easier & more accurate? No, they’re not more accurate, and they’re a LOT more expensive. ---
**Author:** ![Bluffcityguy](https://avatars.discourse-cdn.com/v4/letter/b/ebca7d/32.png) [@Bluffcityguy](https://boards.straightdope.com/u/Bluffcityguy)\ **Post date:** [April 7, 2009, 5:00pm UTC](https://boards.straightdope.com/t/98-6/491695/29 "2009-04-07T17:00:56Z")
> [@Philster](#): > > It’s a lot like the dopey weather people’s forecasts. If the average high temp on April 6 in Philadelphia, PA, USA is 60 degrees and the forecast shows it will be 57, they will show this as ‘below normal’, when in fact the only thing below normal is their I.Q. “Do you know what ‘meteorologist’ means in English? It means **LIAR!** ” --Lewis Black Cheers, bcg ---
**Author:** ![Napier](https://avatars.discourse-cdn.com/v4/letter/n/ce73a5/32.png) [@Napier](https://boards.straightdope.com/u/Napier)\ **Post date:** [April 8, 2009, 10:11pm UTC](https://boards.straightdope.com/t/98-6/491695/30 "2009-04-08T22:11:09Z")
> [@Philster](#): > > An average is a **not** a predictor. > > If the average body temp is more accurately determined to be 99 by years of studies on numerous people, you can’t (and shouldn’t) expect to have your body temperature read as 99. > […] > **An average is NOT a predictor.** I don’t understand why you say an average is not a predictor. I think it is a predictor, and is the best predictor in a certain narrow sense. It’s almost certainly one of the best predictors that are so easy to estimate. If average temp is 99, you can’t expect to have your body temp read as 99, I agree with that. Sort of. Its meaning is unclear if you don’t specify a range, like “within 1” or “within 1/10”. But this suitably clarified statement is true because a predictor does not by itself justify an expectation of a matching value, not because an average isn’t a predictor. In fact, in the sense understood by statisticians, “predictor” is a good description of what an average is. A prediction is an attempt to say what to expect, what typical is (and not an attempt to say what will happen at some future time, which statisticians would call “forecasting” instead). At least, this is how I understand it - can you say more about why averages would not be predictors? ---
**Author:** ![Napier](https://avatars.discourse-cdn.com/v4/letter/n/ce73a5/32.png) [@Napier](https://boards.straightdope.com/u/Napier)\ **Post date:** [April 8, 2009, 10:19pm UTC](https://boards.straightdope.com/t/98-6/491695/31 "2009-04-08T22:19:39Z")
To go a little further with this point about averages being predictors, see: [http://www.amstat.org/PUBLICATIONS/JSE/secure/v8n3/preston.cfm](http://www.amstat.org/PUBLICATIONS/JSE/secure/v8n3/preston.cfm) and in particular look at the section entitled: 4.1 A General Expression for Normal Theory Prediction Intervals [Previous page](https://boards.straightdope.com/t/98-6/491695.md?page=1)