> What decision-making process led to the idea of injecting human urine into a frog in the first place?

In the 1930s, two South African researchers, Hillel Shapiro and Harry Zwarenstein,[26] students of Lancelot Hogben at the University of Cape Town, discovered that the urine from pregnant women would induce oocyte production in X. laevis within 8–12 hours of injection.

-- from https://en.wikipedia.org/wiki/African_clawed_frog#Use_in_res...

The reaction is to Human chorionic gonadotropi - basically it's a marker which tells a human's body "You are pregnant, proceed accordingly". If you've got a womb and are in a reasonable age range this almost certainly means you're pregnant, if not it's a sign something went badly wrong. So, testing whether this marker is present means you know months earlier than you might otherwise.

Presumably the frog "Make eggs now" marker is different, but not different enough to ensure this effect doesn't happen, after all ordinarily frogs wouldn't be exposed to the urine of pregnant humans.

> Will Welsh clawed frogs be the next species that we thought were gone but had just become better hidden?

This isn't a rare species. It just wasn't in Wales and now it once again isn't in Wales. So that's like how Wales also does not have kangaroos. No danger the kangaroo goes extinct, there are lots and they're pretty competitive. But there aren't any in Wales (outside maybe a Zoo?) and so the ecosystem there does not have a kangaroo shaped niche.

Speaking of the frog test, there is apparently an old expression "the rabbit died" in English to refer to someone being pregnant. The original test involved injecting urine into a rabbit, killing it after a few days, and examining it's ovaries

https://en.m.wiktionary.org/wiki/the_rabbit_died

https://en.m.wikipedia.org/wiki/Rabbit_test

The frog was an improvement since you didn't have to kill the frog (apparently they could survive the urine injection).

FWIW the rabbit always died whether you were pregnant or not :(.

> What decision-making process led to the idea of injecting human urine into a frog in the first place?

Hormones are basically messages sent through an animal's body to signal some change should take place. It was discovered that there was a hormone called hCG produced by the human placenta that triggers "you're pregnant" changes in the body. hCG is also present in the urine.

So if you want to detect a hormone, the idea is you inject it into an animal and see if it triggers the relevant changes (since the changes are usually internal, you generally need to kill the animal to check). So you would look for an animal that responds somehow to the hCG hormone, inject urine into it, and check for the response. Mice and rabbits were first used, but it was eventually discovered that certain species of frog that are highly sensitive to hormonal changes made for much simpler and faster testing.

> What decision-making process led to the idea of injecting human urine into a frog in the first place?

Yeah, it makes me think of how many dumb things scientists really did. I bet, that the most of them are unknown because nothing interesting happened.

>- What decision-making process led to the idea of injecting human urine into a frog in the first place?

such an approach has long history - peeing on wheat is known from the times of Ancient Egypt and it was widely used in Middle Ages too

https://history.nih.gov/illustrated-histories/thin-blue-line...

"Bastard Executioner" series set in 14th century has a scene on using several objects to test urine for pregnancy on.

Urine has long been used in medical testing and treatment. The term diabetes mellitus comes from the sweet taste of patients’ urine, for instance.

Estrogen extracted from pregnant women’s urine used to be used as a supplement for menopausal women. I read recently that some doctors would overprescribe urine tests during pregnancy, bill the patient and sell the excess urine.

Later as an estrogen supplement came Premarin, which is made from pregnant mares’ urine.

I can do you perhaps as well as a one-hour documentary. The science podcast Let's Learn Everything [https://www.letslearneverything.com] had an episode on the history of the use of animals in pregnancy tests. It's fascinating. See Episode 5.

https://rabbitcavern.substack.com/p/do-frogs-know-if-youre-p...

Why is this one frog being captured over and over again?????

> What decision-making process led to the idea of injecting human urine into a frog in the first place?

This story is from Wales.

It's very weirdly worded. Clearer would be: A type of frog which was once used as pregnancy test escaped and colonoised Wales for 50 years.

Came here to say this! So many ways to parse it. But the key issue was not knowing that “pregnancy-test frogs” was the central concept. Without that, the headline is so confusing… at some point I had to consider whether “frogs” was being used as a verb

Me too, right after I got done wondering how an escapee pregnancy test differed from a normal one.

Somerhing to do with heightened estrogen levels probably, those levels increase a thousandfold or so during pregnancy.

(Most?) frogs do external fertilisation; all frog eggs are haploid when they come out of the frog.

Until nature killed it!

Why would you imagine they would be?

> [..] Bristol University conducted extensive long-term research projects on them whilst keeping the location secret.

They kept it secret to not disturb the research they were conducting.

Just a few weeks ago. Annoying, but you can use Reader mode to get through it, for now.