
Why Do Islands Induce Dwarfism? - mhb
http://www.sapiens.org/blog/animalia/island-dwarfism/
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sushid
Islands can also induce gigantism [0]. My understanding is that is the
microcosm allows certain species to thrive or perish and we see a more
dramatic change in size as a result.

[0]
[https://en.wikipedia.org/wiki/Island_gigantism](https://en.wikipedia.org/wiki/Island_gigantism)

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gcatlin
See also Foster's Rule

[https://en.wikipedia.org/wiki/Foster%27s_rule](https://en.wikipedia.org/wiki/Foster%27s_rule)

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davnn
What's funny is that, for us humans, the whole planet is kind of a big island
today isn't it? (Edit: not everywhere ofc) I wonder how large humans will get
in a number of generations from now.

Found an interesting article about that topic:
[http://www.bbc.com/future/story/20150513-will-humans-keep-
ge...](http://www.bbc.com/future/story/20150513-will-humans-keep-getting-
taller)

Looks like we are record holders in height already, let's see how far we can
get!

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joe_the_user
I think regular human size can vary a lot by level of resource consumption -
the principle being the larger the mother, the larger fetus and so the larger
the resulting adult.

Obviously, if a height increase/decrease trend continued for a while, one
assumes genetic variations which aided this would be selected for but it seems
that the change itself doesn't necessarily need genetic as such.

See height increases in Japan: [http://www.nytimes.com/2001/02/01/world/tokyo-
journal-the-ja...](http://www.nytimes.com/2001/02/01/world/tokyo-journal-the-
japanese-it-seems-are-outgrowing-japan.html)

~~~
potatote
From my observation, I notice that a lot of younger generation Chinese adults
are likely to be taller than their older fellow country people as well. I have
many Chinese coworkers and even the female coworkers are at least 5 feet 5
inches or taller (for young male coworkers, they are usually at least 5 feet
8-10 inches). Nutrition certainly plays a big role in determining one's
height.

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hammock
Wouldn't the biggest factor simply be limited resources? The same reason why
the average man was 5 inches shorter in 1750 than he is today.

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duaneb
Actually, Foster's rule indicates that predation being the main threat leads
to smaller animals, while the restriction of resources being the main threat
leads to larger animals.

> The same reason why the average man was 5 inches shorter in 1750 than he is
> today.

This is more likely dietary changes than resource restriction—we may not have
had industrial farming, but the average person wasn't starving either. But you
need access to plentiful, high levels of protein to maximize your height
advantage.

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omalleyt
Foster's rule is actually the reverse of that.

Which can be seen intuitively because non-human predators pick off the weakest
and smallest of the pack.

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taneq
This depends on the size of the animals in question compared with the largest
practical size for an animal in that environment. Large animals will get
larger, because this improves their chance of fighting back against similar-
sized predators (think lion vs. antelope). Small animals will get smaller,
because this allows them to evade much-larger predators (think cat vs. mouse).

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anonemu
I don't know, Polynesians and Samoans seem plenty large to me.

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Florin_Andrei
Yes, but they've been living there for only a few hundred years, or a couple
thousand at most. The article was referring to populations living in island
environments for much longer durations.

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aab0
They also have a very different food, cultural, and military environment than
the isolated hobbits would.

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contingencies
Ideas: (1) Richest foraging environment may be out in the open on the
shoreline. If any other predators are present, or even if there is simply
harsh environmental exposure (sun/wind) then a smaller physical size to take
advantage of shelter may be advantageous. (2) Mountainous interiors. I believe
it is well documented that short people have better luck climbing and
descending steep slopes due to a lower center of gravity. (3) Low dietary
variation or reliance on foraged protein rather than large land mammals. (4)
Safety from predators may lead to a younger age of reproduction, accelerating
change.

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Negative1
Intriguing. I wonder then; does this mean our spacefaring descendants will be
smaller for the very reasons outlined in the article?

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MoonUnitZappa
Many suspect spacefaring will require us to become quite small indeed. It will
become ridiculously uncompetitive to drag around a meat body and pressurized
environment.

Think of something like The Field Circus from Charles Stross's "Accelerando".

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theoh
Seems like only a tiny crazy subset of humans will ever want to give up the
freedoms of having a meat body and being able to move it in a pleasant
atmosphere. After all, what's there to do in interstellar space? The idea of
turning ourselves into space probes is a dystopian, inhuman proposition.

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trhway
the foxes example is interesting as there are foxes everywhere, and the
further into the CA or African desert or into Arctic - the smaller the foxes
are. Pure thermodynamics - like surface/volume ratio - would suggest
otherwise. It most probably has to deal with [lesser] reliability of food
availability, similar like in islands case.

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ascotan
It's the bottleneck effect duh.
[https://en.wikipedia.org/wiki/Population_bottleneck](https://en.wikipedia.org/wiki/Population_bottleneck)
As others have noted Polynesians are huge and didn't turn into dwarves.

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xbryanx
Aspects of this island evolution were part of the plot in the marvelously
detailed sci-fi book from Kim Stanley Robinson: Aurora.

TLDR: Interstellar multi-generation spaceships are essentially genetic
islands.

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adamfeldman
Just finished this novel. Great hard sci-fi space opera.

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UhUhUhUh
Maybe the principle that height is also proportional to speed should be taken
into account?

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sunstone
Imagine the Komodo Dragon on a continent. Yikes!

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bechampion
I live in England , this is true.

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taksintikk
Although they are representational of all islands, Tonga and Samoa disagree.

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donatj
Reading this I had a silly thought: "What if we are the 'giants' of old ?"

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giancarlostoro
Biblical giants? They were half fallen angel, half human. Not many Christians
(and maybe even Jews) believe this, but if you study the context of Genesis 6
and the rest of the Bible anytime it speaks of Noah's flood and judging of
angels, they coincide (especially in the New Testament in the book of Jude)
then there's the Book of Enoch, which isn't in protestant or Catholic Bibles,
but the Ethiopians have it in theirs, and it speaks about how the angels took
human wives to themselves. The Liger hybrid species explains scientifically
the nephelim (or Giants) hybrid species to some degree, how it can be so
massive is explained by the DNA. These are the views of some Christians, but
again, assuming Biblical giants, there's a lot of different factors into play.

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moultano
Man, it would be so amazing if we could somehow attribute ancient stories of
dwarfs, trolls, giants, to humans meeting other hominid species that we
coexisted with.

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digi_owl
Or encountered the remains of, as seems to have been the case of dinosaurs
becoming dragons.

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clock_tower
From what I've heard, dinosaur bones tended to be taken for the bones of
giants, at least in the Middle Ages. Dragons were much older than any
awareness of dinosaurs; most medieval myths about dragons trace back to the
_draco_ standard carried by late-Roman cavalry. (See
[https://en.wikipedia.org/wiki/Draco_%28military_standard%29](https://en.wikipedia.org/wiki/Draco_%28military_standard%29)
.)

This, by the way, means that there really were dragons in sub-Roman parts of
the Dark Ages world: Wales and Cornwall, for example, where draco-bearing
cavalry (including King Arthur's, if there was a King Arthur) were fielded
probably until the 600s or 700s.

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DougWebb
Dragon mythology as an explanation for dinosaur bones seems pretty straight-
forward. I'd even say that "dragon" was just the early word for "dinosaur",
and the mythology is based on an earlier extrapolation of characteristics from
fossil remains than what we use today. A somewhat less strict extrapolation,
but even today a lot of what we 'know' about dinosaurs is pure guesswork.

But dinosaur bones driving myths of biblical _humanoid_ giants? That's a much
bigger stretch. Most dinosaur bones are pretty non-humanoid, and people who
are generally a lot more familiar with human and animal skeletons than we are
today wouldn't mistake one for the other. Also, while dragon mythology is
mostly reasonable based on fossil evidence (except for the flying and fire-
breathing... and gold hoarding) giant mythology is completely different. The
biblical texts and non-biblical books like Enoch give them names and actions
that are much more historical sounding than mythological. You don't get
details like that from big leg bone fossils.

So, I don't buy dinosaur bones as the source of giant mythology.

~~~
clock_tower
I have no idea where dragon myths or giant myths originate; giants are easy to
guess, but dragons are a strangely common belief for creatures with so little
basis in reality. (Plasma cosmology has a very interesting explanation for
dragons, and for a lot of other strange things in human history, but the
physics of that theory are pretty bad.) I'm just mentioning what it is that
dinosaur bones were identified with in the Middle Ages -- centuries before
anyone knew that there had ever been such things as dinosaurs.

(To an extent, dragons fall into the same category as unicorns, griffins, and
phoenixes: not mythology so much as really bad zoology. All four of these
species were believed to exist in the real world as contemporaries of medieval
humanity, sometimes surprisingly nearby -- like griffins in the Caucasus.)

