
Was the Cause of Cambrian Explosion Terrestrial or Cosmic? - georgecmu
https://www.sciencedirect.com/science/article/pii/S0079610718300798?via%3Dihub
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merricksb
Same study discussed 2 days ago:

[https://news.ycombinator.com/item?id=17110874](https://news.ycombinator.com/item?id=17110874)
(82 points/123 comments)

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jesdjkeujjuju
I think it probably went like this: a new feature (hard shells) was discovered
by evolution, which gave so much advantage that all sorts of varieties could
coexist for a while (even sub-optimal ones, as they still had the advantage
over old organisms). Eventually, some winners among the organisms emerge, the
advantage disappears and the sub-optimal variations begin to die out.

I like to compare it to the evolution of computer games. When they became
viable first (home computer revolution), an incredible amount of games was
developed. Eventually doom arrived on the scene and every game became a 1st
person shooter. (Simplified story, of course). Or the dot com boom maybe - for
a while, money was thrown at everything internet related. After a while some
winning concepts emerged, and most of the contenders went away again.

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ufo
One thing to keep in mind is that hard shells are much better at producing
fossils. We don't have as good of an idea of how animals looked before the
Cambrian or how diverse they were because most of them did not fossilize very
well.

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bhouston
This is the standard panspermia argument:
[https://en.m.wikipedia.org/wiki/Panspermia](https://en.m.wikipedia.org/wiki/Panspermia)

I think one needs clear evidence of life on a comet or another planet.
Otherwise it is all circumstantial evidence.

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tim333
One thing that bugs me a about the discussion of evolution in general is it
tends to get treated as a smooth process influence mostly by the environment
but DNA is essentially digital code for building bodies and probably the
Cambrian was kicked off by some mutation a bit like a code refactor that
allowed a lot of body variation subsequently by the changing of a few base
pairs.

A bit like, in a loose analogy the old code was

    
    
        print "protein"; print "protein"
    

and the new code was

    
    
        for i=1 to 2 {print "protein"}
    

so that in the second case a single mutation in the "2" could result in a wide
variety of body sizes.

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zaphirplane
What I don’t get about evolution is why humans haven’t evolved in the last
5000 years probably 10,000 years

~~~
firmgently
The timespan of a generation in humans is about 20 years. So in 5000-10000
years that's 250-500 generations, a tiny amount.

For evolution to happen, a genetic mutation has to endow an advantage that
makes its carrier more likely to survive and reproduce. Given that the
reproductive selection process (which characteristics are attractive to a
mate) is largely driven by cultural norms now, it's hard to see what
advantages are going to raise a person's chances of reproducing. Fashion
tastes change several times in a single generation.

Women are often said to like taller men. Well we are getting taller as a
species [1]. If men prefer a woman with a certain 'look', maybe women are
evolving towards that look (it seems like a much harder thing to quantify).
Manipulative, cheating males have more sexual partners - maybe we're evolving
towards more of that kind of behaviour.

If you're expecting humans to grow extra arms or become super-strong or
something, I don't think it's going to happen. Extra limbs is too 'abnormal'
and culture doesn't like that. Being physically strong doesn't affect chances
of survival in humans any more. Same applies to better vision, hearing... any
super-senses. They don't affect our survival. I've heard people posit that
maybe we'll lose our little fingers as they don't do anything. Same again
though - even if it's true that we don't use them, it doesn't mean that
someone born without little fingers is going to have a higher chance of
reproducing.

Our development happens at a rate much faster than biological evolution now
because of culture (meme vs gene). A lot of what constitutes a modern human is
external (as a thought experiment just imagine what a human would be like if
he'd never spoken to another human, read anything, or absorbed any culture in
any other way). From this point of view, cultural evolution could be seen as
evolution v2.0 as it happens and spreads much more quickly that genetic
evolution.

[1] [https://www.scientificamerican.com/article/why-are-we-
gettin...](https://www.scientificamerican.com/article/why-are-we-getting-
taller/)

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AstralStorm
The interesting question is if human changes are liable to speciate or not. It
is possible that just a few changes would result in biological
incompatibilities. Combine it with differentiating sexual selection and things
might become interesting.

~~~
ak39
Interesting indeed.

If humanity in its current state somehow manages not to destroy itself (and
much of everything else) the probability of speciation of our survivors is
close to a certainty. Not so much as a consequence of natural selection or
sexual selection but of human selection.

If we survive another 100 thousand years, we will inevitably see another
emergent species genetically superior but incompatible with current homo
sapiens. I think that will be an incredible day for humans to acknowledge (the
death/extinction of homo sapiens). We had better sort our differences out
before that day arrives.

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sgt101
Other theories: The sun calmed down enough so that large large organisms be
near the light without being zapped with radiation, the algeal mat that
covered the ocean got eaten by animals and this opened the possibility of
ecosystems, the earth unfroze, the chemistry of the oceans changed.

Anyone heard others?

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psergeant
I feel like at this point it’s not too far-fetched to say with absolute
certainty that earth is in the process of a long-term terraform by some alien
species, and that humans represent the final step of that process, by warming
the earth and making sure carbon is properly distributed through the
atmosphere, as well as collecting and separating the metals that our alien
overlords will feast on. When they’re done feasting on us.

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laumars
It's a terraform project for sure, but not for food. We are actually just
circuits in a massive supercomputer built by pan-dimensional mice.

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Nursie
for a (mildly irreverent) takedown of this piece -
[http://www.iflscience.com/space/new-study-suggests-
evidence-...](http://www.iflscience.com/space/new-study-suggests-evidence-
that-octopuses-came-from-outer-space/)

It seems to be a load of speculation written by people with some sort of
agenda and not a lot of actual knowledge.

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gilleain
> including a chap called Chandra Wickramasinghe

Ohhhh. Glad I didn't read the paper then. I'm sure he has a lot of knowledge,
but he's a bit obsessed by the idea of panspermia.

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soufron
Isnt'it a devil in the box problem ? If life is not from earth, then where is
it from, and why there and not here ?

In my view the only elegant solution is to consider that life can originate a
bit everywhere and cross-polinate everytime conditions are there.

On this issue, I think the Vital Question is a great book :
[https://www.goodreads.com/book/show/23316494-the-vital-
quest...](https://www.goodreads.com/book/show/23316494-the-vital-question)

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mjfl
"We should take the problem of life and PUSH it somewhere else!"

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mrleiter
Not saying that I support this, but it gives an interesting touch to the
creation of Adam in the Bible. In Genesis 2,7 it says:"Then the Lord God
formed a man from the dust of the ground and breathed into his nostrils the
breath of life, and the man became a living being." [1]

In the abstract of the paper it says "living organisms such as space-resistant
and space-hardy bacteria, viruses, more complex eukaryotic cells, fertilised
ova and seeds have been continuously delivered ever since to Earth".

Besides from skipping lots of evolutionary steps, if those organisms have been
delivered to earth by some cosmic object (a hand of God?), then man ultimately
formed from that dust.

I am by no means religious, but it's an interesting thought experiment.

[1]
[https://www.biblegateway.com/passage/?search=Genesis+2&versi...](https://www.biblegateway.com/passage/?search=Genesis+2&version=NIV)

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ak39
It's a thought, that's all. It's not an experiment by any stretch of the
meaning of the word experiment.

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mrleiter
That's exactly what I said.

~~~
ak39
Uhm no, it is not exactly what you said. You exactly wrote:

"...but it's an interesting thought experiment".

Your story is not a thought experiment of any kind. It's just an unstructured,
unverifiable, lacking in continuity idea. It just a "thought" on its own.

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

