Why do women have periods when most animals don't?

The thing muddying the water with stress, is that most things that trigger stress are also bad for the body, and thus for foetal development. Making rats run until they collapse from exhaustion might cause miscarriage, but it's unclear whether that is due to stress-hormone-induced spontaneous abortion, or due to the mother's body using up some micronutrient necessary for the foetus, thus causing a developmental defect which either kills the foetus or stalls its metabolism enough to be detected.

I'm unaware of whether there has been the study of the effects of purely psychological (or synthetic, using injected epinephrine) stress on spontaneous abortion rates.

It's much clearer with fear, though; things that cause a fear response don't tend to harm you (in fact, in an adaptive environment, to the degree that a fear response is created, you tend to avoid harm you would otherwise succumb to) but do trigger spontaneous abortion anyway. This would be much simpler to prove/disprove a purely-hormonal effect.

You can see a collection of these at http://www.unnecessaryquotes.com/

The auther started the blog while at the University of Georgia, so the problem isn't confined to Missouri.

This is a common practice in signs. It's wrong in literary English, but is it wrong in signs?

My pet theory is that quotes for emphasis were popularized in 20th century movie posters, where it was common to surround the movie title in quotations (this is still the accepted citation style in, say MLA style). This is probably wrong, of course.

Italics or bold for emphasis can be hard to hand-write, and the quotation marks for emphasis probably look more legible on chalk signs.

Once upon a time, we weren't supposed to downvote to disagree. Then there was a capitulation, IIRC, and that became kosher. Now, I think things may be back to where we started. I don't keep miniscule track of changes to the moderation policy. (Maybe I should?)

You should understand that jacquesm made a pretty sweet joke.

Before calling names, let's look at the article in detail.

"Of course, I wasn't the only one: most women menstruate. But most other female animals don't bleed outwardly like us. Even among those that give birth to live young as we do, only a handful of species menstruate."

So the term menstruate is used to mean to "bleed outwardly like us".

"If the woman doesn't get pregnant, progesterone levels begin to fall. The thick endometrial tissue with its blood vessels then begins to slough off, and passes out through the vagina. This bleeding is menstruation."

So they are expanding on the term menstruate. Now it's both "bleed outwardly like us" and "The thick endometrial tissue with its blood vessels then begins to slough off, and passes out through the vagina"

"On average, women lose 30 to 90 ml of fluid over 3-7 days of menstruation. We know, because scientists have given women pre-weighed pads and tampons, and weighed them again after use."

Clarifying the term menstruate and showing how to measure it. I'm going to paraphrase the definition of the term. So at this point, when they talk about menstruation, they are talking about a blood like fluid, that can be measured, and that happens when the the tissue and blood vessels pass out of the vagina.

The article has a break to talk about the history, theories, and research that has happened over the years. After that they get to the main point. "To figure out the truth, we need to compare animals that do and don't menstruate."

"Great apes do it too. Menstrual bleeding is easily detectable in chimpanzees and gibbons. However, gorillas and orang-utans bleed less copiously, so menstruation is only visible on closer inspection. Other primates, such as tarsiers, may also menstruate, but there is little hard evidence."

They re-iterate key parts of the term. When this article talks about menstruation, they are specifically talking about detectable bleeding.

Now we can get to the heart of my objection. They spent most of the article defining their usage of the term menstruation, and how it relates to the research.

The article claims "It seems the list of animals that menstruate is quite short: humans, apes, monkeys, bats and elephant shrews. What do these seemingly disparate animals have in common?", remember the definition they use for menstruate, blood and tissue passing though the vagina.

If you've ever owned an unfix female dog during heat, you'll be quite aware that they do, in fact bleed out their vagina for a period of time during their reproductive cycle. This fits with their definition.

The only mention of dogs is: "In dogs and cats, the foetuses dig in a little more. But in humans and other primates, a foetus will dig through all the womb lining to directly bathe in its mother's blood." This does not specify why dogs do not fit into their term. In fact this seems to support that dogs have a very similar cycle to humans.

So my question remains, Why are dogs excluded? They never acknowledge the contradiction. So either the article incorrectly sets up the terms, or they don't want to talk about dogs because it doesn't fit the narrative.