
Why would an animal lose its brain? - breitling
http://www.bbc.com/earth/story/20150424-animals-that-lost-their-brains
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caf
The alternative hypothesis - that the brain has independently evolved twice -
is in my opinion even more interesting. If true, it would seem to have
implications for estimates of how easy it is for life to evolve intelligence.

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netcan
Whatever the origin of the brain organ in evolution, There has certainly been
a lot of novel inventions after that time. A lot of interesting "design" has
happened for a long time after that invention, separated by divergence.

Cephalopods are very distantly related to us. Our last common ancestor with
cephalopods is also our last common ancestor with slugs and hookworms. Yet
many species are obviously highly intelligent. Their intelligence seems to
work very differently from vertebrate intelligence.

So, it's interesting thing that some descendant species of whoever invented
brains opted out. But either way some sort of convergence _did_ happen. Maybe
brains evolved twice. Maybe they evolved many times from a common primitive
nerve bundle that performed a very different function. Maybe this happened in
a tangle of back and forth.

The aye-aye lemur and the striped possum both evolved a long bug catching
finger. We know that it's convergent rather than common ancestry because
(among lots of reasons, but this is a neat example) it's a different finger.
But, they both had fingers to elongate in the first place. So, given the same
machinery to evolve and the availability of similar ecological niches (no
woodpeckers, lots of bugs) they came up with a smiler solution.

We know that brains, and their components are very flexible even in a mature
organism. So it makes sense that evolution is wild and creative, repurposing
the tool constantly. I mean the diversity in sense perception in different
animals seems like evidence of radically evolving brains over relatively short
periods of time. Even entirely new senses (eg echolocation) seem to evolve
fairly easily and quickly.

TLDR: depending on what your precise definition of "brain" is, this seems very
likely. Aye-ayes & striped possums both have elongated fingers that evolved
separately from regular fingers. The fact the they both evolved from regular
fingers is interesting, but neither here nor there for most interesting
conclusions. Brains are probably like this, but way more interesting any
mysterious.

^I feel like I have to credit Douglas Adams who wrote beautifully about these
animals.

~~~
caf
So I was using "brain" in the same sense as the article, as a shorthand for
"central nervous system".

I think we already knew that once you acquire a CNS, it can evolve rather
rapidly to quite complex brains, and that doesn't seem intuitively surprising.
It's that first leap to a basic nervous system which seems like the high
activation energy barrier, and if it may have happened twice rather than just
the once, then I find that interesting.

~~~
netcan
The 'earliest known example' (520mya) discussed dates to around the cambrian
explosion, the geological period where the fossil record is rich with
"earliest examples" and type specimens for phylums.

Maybe another way to put it is 'The definition of brain used in this article
might apply to organs other than the brain in modern species." It's basically
a nervous system, centralized or not. Who knows what it did or what it was
for. It may have a predecessor outside the animal kingdom. Plants have sensory
perception, or some version of it.

I'm not disputing the claims in this article or anything else. I'm basically
agreeing with you.

Whether or not some nervous system, nerve cells or complexes of nerves evolved
520+mya and were 'lost' in some phyla or was evolved through convergent
evolution a little later, it's partially a semantic issue: do we call
something a brain. Most of what makes a brain a brain probably came later and
evolved separately in different phyla. This means radically different ways of
doing things.

BTW, Richard Dawkins really turned me on to evolutionary biology (a side gig,
when he's not arguing with dummies) in some of his books. "Ancestors Tale" is
awesome for really getting the "phylogenetics" way of thinking discussed here.

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spiritplumber
For the same reason why, say, version 7 of the WRT-54G router had half the
memory that version 2 had.

It's expensive (money or calories) and the extra functionality doesn't help in
getting more out there (selling or reproduction).

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skywhopper
Key point: evolution does not necessarily working towards more complexity or a
specific endpoint. Rather, the unique selection pressures that exist when
organisms attempt to reproduce vary, as do the particular genetic changes that
happen due to any number of factors (mutation, viruses, gamma rays, copy
errors, bacterial absorption, whatever). Each generation may face similar or
different pressures. Certain mutations may be more or less likely. In some
cases, the mutations that survive may be pure random chance. In others, only a
specific mutation may have saved the organism's particular genes from
extinction. The future organisms and genes that emerge from this chaotic
process are unpredictable. Sometimes those organisms will lose features,
sometimes gain, sometimes have weird changes that don't appear to make sense.
All that matters is: do the organisms continue to reproduce successfully
generation after generation?

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WalterBright
Plants have also survived for hundreds of millions of years with no brains.

~~~
grondilu
Indeed. My memory is failing me but I seem to recall having heard or read
someone talking about the brain and stating that its sole purpose is to move
the body. Thus, an organism that does not move does not need a brain, and as a
proof of this idea he mentioned that some animals, like some medusa, loose
their brain once they fix themselves to the floor (turning into polyps in the
case of medusa).

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joeyo
Daniel Wolpert has a TED talk where he makes this point [1]. And I think he's
basically got it right. Certainly there are organisms that can move without a
nervous system (single celled amoebas, venus fly traps, etc) but by and large
you need an (electrical) brain if you are going to react to something on a
fast timescale.

1\.
[http://www.ted.com/talks/daniel_wolpert_the_real_reason_for_...](http://www.ted.com/talks/daniel_wolpert_the_real_reason_for_brains)

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edem
So if someone does not use his brain for long he/she becomes demeted becuse he
does not need a brain?

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holychiz
what?! no joke about our bosses? oh right, you're all your own boss here. :)

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beaner
Another example of where more brains doesn't necessarily mean evolutionary
advantage is modern humans. It can be seen all over the world that the less
intelligent procreate more.

The intro to Idiocracy makes the point well:
[https://www.youtube.com/watch?v=hL1-340ODCM](https://www.youtube.com/watch?v=hL1-340ODCM)

It's kind of a joke, but also really not. It's frightening.

~~~
vog
_> It's kind of a joke, but also really not. It's frightening._

It is a joke.

Idiocracy relies on the assumption that the "more intelligent" people are
snobs and too busy and too perfectionist with their life to have children,
while the "less intelligent" people are mostly having sex and are too lazy to
apply contraception properly.

Essentially, the first half of the movie is a justification for elitism.

I'm less afraid of Idiocracy to become true, but more afraid of politicians
acting as if they believed in this movie.

The second half of this movie is more interesting, though. It may be
interpreted as an analogy of how the most gifted people (in the sense of
"intellectual giftedness") may feel living in today's world. (by putting
today's "normal" people into a dumb world) But even that is, of course, a
funny hyperbole, and nothing to take too seriously.

~~~
beaner
Have you ever heard the phrase "there is truth behind every joke"? It is
relevant here.

The joke is in the exaggerations and charicatures. The truth is what is real
that would cause this joke to be made in the first place.

Obviously smart does not equate to "snobbery" or "perfectionism". And less
smart does not equate to "more horny". It is a comedic layer added by the
directors to make you laugh, because it is a comedy.

But the truth beneath the funny is that less smart people generally make
poorer life decisions. For many people in many contexts, less children for a
longer time is a smart life choice, and more children more quickly is not.
Because more children more quickly is, in most contexts, in the category of
poor decision, it tends to happen more with less smart or educated people.

I don't see how it is an argument for elitism at all. It's an argument for
promoting education.

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wobbleblob
But do you have evidence for the assertion that there is a negative
correlation between intelligence and reproductive success? I read somewhere
(can't find the source) that smart guys on average actually have more children
than stupid ones, and that for women fertility is about the same.

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newuser88273
I've seen multiple sources showing reduced fertility in high-IQ females
(across multiple countries.)

The culprit, however, doesn't seem to be raw intelligence as such, but modern
western education, which seems to have a dose dependent sterilizing effect on
females. In that light, high IQ isn't fertility-reducing in itself, rather low
IQ is protective against modern western education.

~~~
saiya-jin
Would love to see some proper evidence for these claims. One can easily see
that clever ladies tend to focus much more on long education/career, rather
than jumping straight on babies-making bandwagon. Also, finding good partner
to have kids with seems much harder for them (well, for clever guys sadly
too). Considering most university level education ends when people are around
+-23 (not even going into PhD ones), and then they just become fully
autonomous and step in working treadmill (earn->spend->earn-> cycle), I would
name culture/work/environment situation or pressure for that.

Also generally, more clever people focus more on quality rather than quantity,
and babies are no exception. Norm are 1-3 kids, not because women are not
fertile anymore (unless climacterium is reached), rather time & resources are
considered.

Even this is very simplistic & dumbed down view on these matters.

