When this question was recently posted I voted to close it based on it being either too broad or primarily opinion-based. Take your pick.

The OP pointed out there is a lengthy history of "anatomically correct" questions that frequently ask for insight into the evolutionary possibility of mythical and/or fictional creatures.

Have I missed something in the FAQ? Are they actually on-topic? Or are they on-topic by default simply by their volume and the precedent they set?


If "How could X evolve?" questions are on-topic

Then I recommend we modify the FAQ to specifically say so as they are (insofar as I understand the rules) 100% opinion-based. I'm actually interested to see if someone can convince me they are not 100% opinion-based. To prove my point, I'm willing to post the question, "Anatomically-correct: how would a one-eyed, one-horned, flying purple people eater evolve?"

If "How could X evolve?" questions are off-topic

  • We need to close a bazillion questions to remove the precedent.
  • We need to close @Tres-2b's current bounty.
  • $\begingroup$ Regarding the title of these questions, I feel my finishing paragraph in my answer to Are questions based on movies okay? is as relevant as ever. $\endgroup$
    – user
    Dec 14 '17 at 8:31
  • $\begingroup$ OooooooOOOO...I am the ghost of precedent past.....respect meeeeee......worldbuilding.meta.stackexchange.com/questions/5652/… $\endgroup$
    – kingledion
    Dec 14 '17 at 10:51
  • 3
    $\begingroup$ @kingledion, Your post is useful but for one statement, "The standards don't change over time." The problem is that the standards do change over time and have changed over time. If precedent is allowed to exempt from today's laws, today's laws are worthless. $\endgroup$ Dec 15 '17 at 15:26
  • $\begingroup$ @MichaelKjörling, that was a useful post and I wish all the "Anatomically Correct" questions adhered to it. I'd have no problems with them. $\endgroup$ Dec 15 '17 at 15:29
  • $\begingroup$ @JBH thank you for bringing this to my attention. $\endgroup$
    – TrEs-2b
    Dec 15 '17 at 20:45

Improperly Constrained

The fundamental problem with "too broad" and "opinion based" is a lack of constraints in the question. Someone asking "How do I evolve a creature to be like X?" without placing some constraints on environment and other pressures should be closed.

I'll grant you, the style of questions we are discussing do tend to be over-broad as it's difficult to sufficiently constrain them. However, as a category, I don't think it's appropriate to blanket ban them since that eliminates the potential for someone to write a sufficiently constrained question.

  • $\begingroup$ This is a good point, and on a creative site (that just barely fits within the concept of Stack Exchange in the first place) there needs to be some leeway. But that puts the burden on "us" the people who manage the FAQ to provide clear explanations of what constraints are required for questions that, as a pattern, fail the general rules. However, "How does X evolve" questions require (IMHO) nearly godlike insight to answer with any hope of objectivity. What constraints can be described that are predictable and repeatable? $\endgroup$ Dec 14 '17 at 17:05

At the request of @JBH I am going to point out that evolution has rules and restraints. It is a game of cause and effect where every form must serve a function and those functions can not contradict.

If a creature has a certain form, then it biologically has evolved that form. Yes, there are multiple ways it could have evolved it, but some are way more likely than others. There are many questions on this site where multiple, different correct answers can be given, but the quality and likeliness of these answers allows for a 'correct' answer to be chosen by the OP.

  • $\begingroup$ Note that correct answer should not only be chosen by OP, but the community as well. That's one of the measure of "too opinion-based question": a question that is the sole reason an answer can be "correct" is OP's preference. $\endgroup$
    – Vylix
    Dec 18 '17 at 7:42
  • $\begingroup$ @Vylix unless i mistaken what you mean, i disagree, the best or correct answer should be the OP priviledge to decide, just because many people upvote certain answer more because its more appeal or seem agreeable by the mass doesnt correlate to be the best or correct answer, and it doesnt imply such answer is 100% correct or factual, i has seen some misleading or bias answer or even simply base of the user status or reputation number to get more upvote. $\endgroup$
    – Li Jun
    Dec 4 '20 at 1:06

The question looks incredibly broad to me. We are unable to answer this question for real world creatures. "How does a dog evolve?" doesn't make sense as a question.

Additionally "How does x evolve?" isn't about the creature being anatomically correct either.

There have been questions (like these about furries, charybdis, and insectoids) asking about anatomically correct creatures that have been closed before. Whether these questions are acceptable should be handled on a case by case basis.

If you look at other questions in the anatomically correct series, they are asking about how could creature X exist in a physically plausible way. My general test for any question is to look at it in it's simplest form first. The core of this question about Nachtkrapp is:

How close can I realistically get to my harbinger of death, the Nachtkrapp?

Most of the rest of the question is spend describing what the significant features of a Nachtkrapp are.

So while I think the question you linked should be closed I don't think there is a need to revisit the whole series.

  • $\begingroup$ I would generally agree, but the very first question on the list is this one, which asks "how does X evolve?" The list is being used to declare a precedent. Doesn't that require us to revisit the entire list? $\endgroup$ Dec 14 '17 at 4:35
  • $\begingroup$ That question asks a bunch of rather similar questions at once. Most of the answers seem to focus on "how close could I get to the classic griffin?" which seems to be the core question of the series. $\endgroup$
    – sphennings
    Dec 14 '17 at 4:39
  • $\begingroup$ The answers are a great measure of how inappropriate the entire line of questions is. But that's not the issue. The new user isn't using the anwers to justify her question, she's using the question, which appears to be outside our rules as it stands and is setting a bad precedent. (Indeed, at a glance it appears all of Tres-2b's "anatomically correct" questions fall short of the rules.) $\endgroup$ Dec 14 '17 at 4:44
  • $\begingroup$ If the Gryphon question was newly asked today I'd probably make some remark about perhaps narrowing the scope a little bit. (they're asking a lot of questions, but they're all somewhat related) but I wouldn't VTC it. If you feel that it isn't acceptable under the current rules you should VTC even on old questions. $\endgroup$
    – sphennings
    Dec 14 '17 at 4:47
  • $\begingroup$ Your accepted answer for that question reflects what I've been told on other sites, especially StackOverflow. The process of closing old questions is obviously slow and tedious, but the linked question I refer to in the post is an example of the problem. If the old questions aren't closed due to today's rules, people use them as precedent to vacate the rules. You could interpret my question here as an invitation for authorization to begin closing the "anatomically correct" questions that are actually "How does X evolve?" questions. $\endgroup$ Dec 14 '17 at 4:53
  • 3
    $\begingroup$ @JBH The general idea as I see it is, that there's no reason to go hunting for old questions but once they're brought to our attention they're fair game. $\endgroup$
    – sphennings
    Dec 14 '17 at 4:57
  • $\begingroup$ I agree with that completely. $\endgroup$ Dec 14 '17 at 4:59
  • 3
    $\begingroup$ @sphennings is correct about there generally being no need to hunt for questions to close. However, if one comes across them for whatever reason, including just leisurely browsing the "related questions" in the sidebar or poking at some interesting tag, then my opinion is that it's always worth considering whether one should flag or VTC that question based on the current standards of the site. If it's brought up explicitly by somebody, then it's definitely fair game in my book. $\endgroup$
    – user
    Dec 14 '17 at 8:34

Evolution does not take place in a vacuum. We can't say if some sort of life form could evolve if we don't know where it is supposed to live now, and preferably where its ancestors might have lived, though that isn't strictly necessary.

We also have the constraint of the life forms that it is supposed to live near, and the biochemistry of the world in question. In many of the Anatomically Correct series, these constraints are supplied by implication: these creatures being the myths of certain peoples and being said to live in certain places and in certain ways, and therefore must live alongside other real and mythical beings of that environment.

The OP's example of a "One eyed, one horned flying purple people eater" should be off-topic unless somewhere between the stated intention and the act of actually posting the question, more details are provided. Otherwise, I could answer:

A One-eyed, One-horned Flying Purple People Eater is a species of vulture characterised by dark purple feathers, with a single light bony protuberance on its head that looks like the horn of an animal such as a rhinoceros. They are named "One Eyed" because the real eyes have black irises and blend in with the colour of the black skin of the head, but on the forehead, between the beak and the horn is a structure that looks like a single large eye with a white sclera, a blue iris and a black pupil, however this structure is not a functional eye, but, along with the horn, serves as a device to attract mates.

Historically, these birds have been seen on battlefields, devouring the corpses of deceased soldiers. They prefer to eat carrion that is similar in size to a human or smaller, as their horn prevents them from inserting their beaks and heads any further into the carrion than ten to twelve centimeters, which is typically sufficient for human-sized carrion, but insufficient for carrion such as a horse, hence why they prefer eating "people".

  • $\begingroup$ It's funny how life works. I'd completely forgotten having posted this question. And here I am just a day or two ago talking with an OP trying to post an ACS question that isn't asking about the creature's anatomy, but solely about the creature's evolution. Personally, I loathe "how could X evolve" questions. We barely understand how humanity evolved, less about anything else terrestrial where testing can occur, and next to nothing about simulating arbitrary evolution. I could be wrong, I'm not a geneticist, but the answers seem fictional by definition. $\endgroup$ Dec 3 '20 at 16:50
  • $\begingroup$ BTW, as I understand the ACS, your proposed answer for a OEOHFPPE would be pretty good. On the other hand, your post doesn't seem to answer my question. Should ACS questions strictly focus on the anatomical description of the referenced creature, or should ACS questions be expanded to permit asking about the evolutionary path of said creatures? Where do we draw the line for the ACS? $\endgroup$ Dec 3 '20 at 16:53
  • $\begingroup$ @JBH as far as evolution goes, you have a vulture... and during speciation it evolved a unique set of sexual attractant features. Little more need be said. $\endgroup$
    – Monty Wild Mod
    Dec 3 '20 at 21:03

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