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I was inspired by the "Given Any Thought to Lifespan?" thread, but I thought that this might warrant its own discussion instead of being included there. Therefore, I've created a new thread. I apologize if that was a stupid idea. (That happens to me a lot.) Also, I'm sorry for the extra-long post; I couldn't fit everything in even with it being this long. sweatdrop

Now! The discussion of this thread is to debate the maturation of demons, or, more specifically, when demons are considered fully mature (meaning, sexually.) For all intents and purposes, I have accepted the idea that Hiei is less than 100 years old during the end of the series and that Yoko is over 1,000.

(If you disagree, I apologize, but this isn't the place to argue about it. borderline_mary has a thread about it in the Hiei forum, and kudos to her for the theory to begin with.)

Consider. The age of when a species is sexually mature is defined, from an evolutionary standpoint, on the best time for the entire species as a whole. For instance, elephants usually become sexually mature around age 10, and they live to be around 60. They can produce about four offspring in their lifetimes. Due to being hunted and harsh environments, this is a good rate because it will keep the population steady without overpopulating the planet (in theory.)

Humans, alternatively, are usually mature at around age 12, often live to be 70 (and sometimes much longer) and can produce as many offspring as possible within those years (the amount we actually produce is averaged at 2-3, but a woman can have as many as twenty kids in this time, and sometimes more.) However, after age 45, most women stop being able to reproduce, leaving around a thirty-year window for reproduction. This also might be a newer development due to overpopulation.

All of this, then, would be in proportion to a demon's life. Of course, we don't know how long the average demon lives if allowed to die a natural death. Hiei seems to be adultish, at least mentally, before 100. Of course, he is part koorime, and their lifespans go on for, as far as we can tell, millions of years. However, we know that some demons (including Yoko and Raizen) can live to be at least one thousand years old.

For all intents and purposes, let's say that the average lifespan for a demon who is able to die naturally is 700 years old. In the case of humans, sexual maturity is reached about 1/6th of the way into life. Thus, an average demon would be mature at around age 117.

(Making Hiei not old enough to be considered an adult. Even discounting his lineage, which would actually make the age of maturation later in life. For instance, if koorime live to be 7 million years old, then they would be sexually mature after one million years! The problem is in the fact that we know that koorime begin having children after one hundred years of age. borderline_mary has already discussed the disadvantages of living for millions of years and breeding every one hundred, so I won't go there.)

It is possible that koorime are a major exception to the rule, or that Hiei's fire-demon lineage make him mature faster than normal for a koorime. From there, we can begin to ask, from an evolutionary standpoint, whether demons mature faster or slower than humans.

One of the theories that I've heard as to why humans take longer to mature has to do with intelligence. Originally, because many of them seem to be intelligent, I thought that demons took longer to mature. (Also, because they live so much longer than humans do.) I realized, however, that they may take longer, but not necessarily in proportion to humans. For instance, it may take us 1/6th of our lives to become mature, but it might only take demons 1/12th of their lives.

Why? Firstly, because not all demons are intelligent. I am willing to consider that intelligence/power is hereditary in demons, however, the class system in YYH is used to show that it is always possible to gain more power, and so that makes me wonder. Additionally, it seems to be that the more powerful/intelligent a demon is, the longer he lives. (Of course, that could just be survival of the fittest, in a literal sense. However, intelligence, power, and a long life are all seemingly intertwined when it comes to demons, and correlation does not prove causation.)

I also wonder whether intelligence comes inherently with more power, or if it takes an intelligent demon to gain such power. (Consider demons such as Balldock or the other less-human ones throughout the series. As the show went on, the enemies became more powerful and more intelligent, to the point where they didn't seem to have demonic forms any more.)

Another point is that demon world is a harsh place. It is probably rare (some may even say impossible) to find a weak demon that lived the course of its life. As we know, the rate of replacement increases when the risk of children dying is higher. (So, in a peaceful society, families might have two children. In a society where it is more likely for children to die, families will have more like six or seven children.)

This leads me to believe that demons have many more children than humans do, and they are whittled down by the harsh environment. In order to have many children, it's necessary for demons to become mature earlier in life, especially if they have shorter lifespans.

Of course, all of the above requires that demons evolve in the same way as most other species, and that their being supernatural has no weight on the issue. (It very well might, but I can't think of how to deal with that now.)

At any rate, those are my thoughts. I hope you read this far, and I hope someone will be able to debate/agree/etc. on the issue. I only have one request for this forum: that it says scientific so as not to violate the PG-13 rule of Gaia and the guild. Thanks for reading!

I'd say this is a tricky subject, because while humans are one single species, it's a distinct possibility that demons are not. Look at the enormous collection of physical permutations, as well as the existence of specific "races" of demons. Somehow I don't think those are equivalent to "races" as they're defined within the human species.

Usually, for two animals to be considered the same species, they must be able to interbreed and produce fertile offspring, and can also be separated as different species if they're not normally disposed to interbreed given the chance. That's why dogs have innumerable breeds, but are almost all considered the same species, while wolves are not the same species even though they can also produce fertile offspring with dogs -- they're not disposed to mate with dogs, even though the offspring would be viable.

To be perfectly, frankly honest, we don't even know if ice demons and fire demons are the same species under that definition, because for all we know, Hiei and/or Yukina might be sterile, like a mule or a liger (I just totally shot my age theory in the foot with that possibility, didn't I). To compare demons as a group with humans as a group doesn't necessarily make sense, because there are so many different sorts that we see, and who knows whether or not they're even close to the same species? It's hard even to say that they're different species because they aren't disposed to interbreed; with animals, usually it's instinct or predisposition of pheromones/hormones that determines attraction, whereas between two sentient species, the "disposition" line is solidly blurred, because even semi-intelligent beings can and often will act outside of instinct and against pheromones/hormones.

Given that, I'm inclined to agree that the lifespans vary wildly among demons, depending on what sort/species they are. I'm not sure if inferring millions of years for the koorime lifespan is something I'd venture, since all it says (IIRC) is "long to the point of seeming endless", which is a pretty subjective qualification if you ask me. There are, however, a bunch of demons running around that are clearly still in their prime at over 1000. I suppose demons with million-year lifespans aren't out of the question, but I'd figure it for being problematic at best to assume.

As for the intelligence factor -- doesn't the series itself say that intelligence and strength are usually linked? I believe that's what I recall. It's also worth noting that most demons who are very, very strong are much more human-like than those weaker. At the very least, we know that some demons can and do interbreed with humans, although I imagine it's not very common, which would technically put those demons and humans under the heading of separate species, but only because they're not usually disposed to interbreed. But are humans fertile with lower-level, more bestial demons, or is the species line drawn somewhere along power/intelligence lines?

To cut my very long-winded post short, it's really impossible to say when sexual maturity comes to any given demon, because we have no scale for comparing them with each other or with humans. It's like asking what the sexual maturity is for mammals -- it depends on which ones you're talking about. I will say, however, that given the harsh and unpredictable environment of the Makai, it's likely that the trend among demons is to reach sexual maturity sooner rather than later, and probably at least sooner than humans relative to their respective lifespans.

(Feel free to shoot me for babbling.)

Personally, I like babbling. Lol, but probably only because I do it all the time. ; D

A question just came to mind that InkMistress brought up in her original post. Do demon females have menopause? Will they at one point be unable to reproduce?

I believe the koorimes would have to at some point, because of overpopulation. But as for the weaker demons, I'm actually unsure. I mean, I would think they would keep reproducing until death because of how quickly they're wiped out.

As for the stronger demons I'm not too sure either. I would think they'd be similar to humans in only having a few children, but seeing how long they live if they have menopause at all, I would think it'd be a very very long time away...

Contributions anyone?

I would hate to meet a demon on menopause. or her period. OO.

*blows half the room away* Get me a SOUL NOWWWWW I am hungry!!

Well, it could technically go either way. Having twins doesn't necessarily mean that they aren't supposed to just have one child each. I think, in the series, that it was noted as uncommon for twins to occur; Hina's birth to two children, and her shedding of two special tears instead of one, was prominently commented on by more than one person during flashbacks and descriptions. Twins can happen from a single fertilized egg, after all, and although you would normally get genetically identical twins out of that, who says that's how demons work? *shrug*

Hahaha. That would suck on SO many levels. Hope they're well supplied in their female products. Lol ; D

How often do you think higher level demons would ovulate? I'm starting to think in terms of multiple months/years!

I'm afraid I...don't know what you mean. Could you explain please? : )

I agree with the folks who say there's no real way to tell.

When dealing with demons there's no guarantee that they'd be at all analogous to humans.

And I really doubt this is something the mangaka gave any thought too at all.