
Moore's Law and the Origin of Life - tocomment
http://www.technologyreview.com/view/513781/moores-law-and-the-origin-of-life/
======
Udo
Another day, another panspermia article. So transistor density and publication
frequency follow a very strict exponential rule and that rule can in turn be
used to trace the time elapsed to their origins. Most systems though don't
follow such a rule, and if they do they generally don't at the extremes of the
graph (near the beginning and after a long time).

That said, the estimated 9.7 ± 2.5 billion years for life to evolve is at
least within an order of magnitude correct, which makes it pretty cool. Also,
we don't know how long abiogenesis takes and through which stages (presumably:
many) the whole thing has to go until even the most basic building blocks as
we know them today are set up. So you can add X billion years on top of that
estimate while you're at it.

Does that prove anything? Absolutely not. But even without evoking the tiring
panspermia hypothesis this result is interesting, because the result is not
completely off. It means that, within a certain period at least, the
complexity of life _does_ follow this exponential rule. Clearly, the formula
needs to be tuned (based on evidence, not on open-mouth extraterrestrial
finger-pointing), but it's a great start. I would venture that a more detailed
genetic analysis of relatively recent organisms might result in a curve that
is much more accurate.

Assuming something will always double within a certain interval is not
detailed enough as a model for this.

~~~
leot
What's so tiresome about panspermia?

~~~
Udo
There is usually not a lot of actual science involved. The motivations for
presenting panspermia papers are in most cases philosophical in nature and it
shows. This paper, too, implies that's what happened even though the accuracy
of the model is highly dubious for a number of reasons.

Compare that to when Hubble first attempted to calculate the age of the
universe by measuring the history of its expansion. It was quite a similar
method: simply roll the equation back in time to where the universe's size was
zero. He got a result that was lower than the geologically known age of the
Earth, in fact we now know he was off by a factor of ten! Refreshingly, people
didn't jump to conclusions though and in time everything fell into place.
Hubble had fallen victim to a systematic measuring error. We are also now
pretty certain that the expansion of the universe was not always linear.
Hubble's method is still valid and impressive, but the tools and models needed
to be refined. It's easy to see that the same applies to this finding.

------
6ren
Those complaining about extrapolation may like to read the paper, rather than
the article...
[https://docs.google.com/viewer?url=http://arxiv.org/pdf/1304...](https://docs.google.com/viewer?url=http://arxiv.org/pdf/1304.3381v1)

There's discussion of measuring DNA complexity; issues in extrapolation
(there's evidence suggesting recent increases are hyperexponential, which
would push back the origin of life even further); section 8 notes function
complexity has increased much faster with the "mind" (as in what birds and
mammals have) which is not reflected in DNA complexity (chimp-human
encephalization rate is x100 faster).

I _love_ the fresh perspective of not tying the origin of life to the origin
of earth - nice and non-geocentric!

~~~
sageikosa
The rise of life doesn't have to be a universally unique event. It can easily
rise in isolation on Earth, and in numerous other places that obey the laws of
organic chemistry.

------
jliechti1
I liked this comment on the article. This is the kind of feeling I had while
reading it:

 _"Lets take 5 data points and project backwards 3x the range of the observed
data. Science! Regression!! There's no way this could be wrong, right?"_

------
surrealize
Ach, this is terrible. Genome size is influenced by a number of factors,
including:

\- Generation length (faster-reproducing organisms tend to have smaller
genomes)

\- Transposons (sections of DNA that use cellular machinery to copy themselves
to multiple places in the genome; they're usually viruses that got
incorporated into the host germline some time in the past)

Genome size isn't anything like a direct measure of "complexity" or
"development"; some plants have genome sizes that are orders of magnitude
larger than the human genome.

The worst part is that they take genome size sampled in the present day across
multiple organisms, and then they assume that some of those present-day
genomes represent genomes from particular points in the past. So the x-axis in
the regression is basically a guess.

I'm not a statistician, but I imagine that fitting an exponential distribution
can make the x-intercept sensitive to data errors.

~~~
kragen
> Genome size isn't anything like a direct measure of "complexity" or
> "development"; some plants have genome sizes that are orders of magnitude
> larger than the human genome.

What makes you think those plants aren't more genetically complex and
developed than we are? A lot of our complexity is non-genetic.

> I'm not a statistician, but I imagine that fitting an exponential
> distribution can make the x-intercept sensitive to data errors.

You mean exponential growth, not an exponential distribution, and exponential
growth never hits the x-axis.

~~~
surrealize
> What makes you think those plants aren't more genetically complex and
> developed than we are? A lot of our complexity is non-genetic.

The real problem is that "complexity" and "development" in the context of
evolution aren't well-defined. So the way that they place genomes on the
x-axis is really arbitrary.

> You mean exponential growth, not an exponential distribution, and
> exponential growth never hits the x-axis.

Right, exponential growth. And yeah, the horizontal line that they're
extrapolating back to isn't the x-axis, it's the y=1 line. The point remains:
roughly speaking, it seems like small changes to the curve could produce large
changes to the x-coord where y=1, since the curve is so close to horizontal
there (on a linear-linear plot), right?

~~~
kragen
I imagine they're using genome size (number of bases in exons) as their
measure of complexity, not something ill-defined.

I don't think it's sensitive the way you say, since they're basically just
linearly extrapolating the logarithm, but I haven't read the paper. If you
somehow manage to shoot high or low by a factor of 100, that's only a temporal
error of six or seven doublings. The bigger issue is that they're
extrapolating over orders of magnitude that we have no direct evidence about.

~~~
surrealize
> I imagine they're using genome size (number of bases in exons) as their
> measure of complexity, not something ill-defined.

They're taking genome size and trying to relate it to time. And the way that
they're doing that is to take organisms from the present day, and imagine some
of them in the past. The less "developed" or "complex" an organism is, the
further in the past they put it. That process is the flawed part.

In other words, the y-axis (genome size) is well-defined, but the mapping of
organisms onto the x-axis (time) is not.

------
rflrob
Extrapolating back to when the genome size was 1 probably doesn't make sense,
but what this approach might be able to do is suggest the smallest functional
genome size, about 10,000bp based on my reading of the graph.

It's also worth pointing out that we don't, in general, have a way to know
what portions of the genome are truly functional, nor even a really great
definition of functional (the ENCODE consortium caught a lot of flak for
theirs as overly broad). Also, almost all the genome sizes we know are from
the modern day: bacteria as a class may be 3 billion years old, but they've
been evolving over those 3 billion years too!

------
taltman1
Notice how they cherry-pick among genomes to get their fitted line. A common
fallacy is to associate genome size with the "complexity" of an organism. Even
assuming that there is a simplistic linear ordering of organismal life (i.e.,
"lower" and "higher" organisms), a "lower" organism like the poplar tree has
more than two times the number of genes as the human genome.

~~~
sageikosa
You mean to tell me evolution isn't about "progress"? ;-)

~~~
writtles
But there has to be some characteristic that certain species required many
evolutionary "steps" to get to. For example, there were no humans OR poplars
one billion years ago nor the possibility yet since their / our ancestors
hadn't yet made the scene.

------
zeteo
I think the problem here is that we don't have the original prokaryote genome.
Today's prokaryotes have gone through billions of years of evolution and might
well have longer genomes than their distant ancestors. So the leftmost points
on the graph might have shifted up over time (albeit more slowly than the
rightmost).

~~~
mbq
Way worse. Evolution is not about gaining complexity but about fitting to
(current state of) the environment; in this manner, Procaryota are actually
the most "evolved" form of life since they can rapidly adapt thanks to their
short life cycle and uncluttered physiology. And this can be easily seen in
genetic diversity -- the whole spread of animals or plants is almost
negligible in comparison
([http://en.wikipedia.org/wiki/File:Tree_of_life_1500px_colour...](http://en.wikipedia.org/wiki/File:Tree_of_life_1500px_coloured.png)).
Another good example is the fact that practically all procaryotic germs are
highly specific, so must have evolved after their host species did.

~~~
writtles
> Evolution is not about gaining complexity but about fitting to (current
> state of) the environment

I'm glad you cleared that up. Here I was thinking evolution and its "goal" is
still a mystery to science.

------
original_guy98
As always, sort of relevant xkcd: <http://xkcd.com/605/>

------
dEnigma
There is a lot wrong with this approach, but even if you agree with their
method there is one thing that seems odd in their analysis. Let's suppose that
life originated before the birth of the earth. Obviously it managed to reach
earth, which would mean it (the organism) had to travel through space for an
extended period of time - the authors claim that it was frozen - so you should
account for that time in the graph, and obviously life couldn't settle on
earth for quite some time because in the beginning our planet was extremely
hot and unsuitable for any kind of life. That would shift their postulated
origin of life further into the past, most likely to a point where there
wasn't even a universe to begin with, or at least no planets that would allow
for the formation of life. [Note: I didn't read the whole paper, maybe they
discussed these points. Also please correct me if I'm wrong on anything]

------
guard-of-terra
They try to put organism's compexity on a logarithmic scale and look where
this line "reaches zero". Then they find out it was very very long ago, before
the Earth coalesced. They then proceed to imply that life is older than Earth.

The problem here is: you can't do that. For example, if you look at human
population, it was growing kind of exponentially for as long as we know. And
if we continue this trend long enough to the past we'll infer that Earth
featured several dozens of humans even when it was still in a liquid magmatic
state five billion years ago!

Exponential growth becomes glacially slow when we go back in time. Therefore,
any growth seems to be not exp(t) but rather max(ct, exp(t)) - not slower than
linear. It doesn't matter once we hit present history, but it does matter when
we talk about a linear part in the past.

------
rouli
This is fun! I took the boys average weight data given in [1]

months from conception, average weight (kilos)

(9, 3.25)

(15, 7.5)

(21, 9.97)

(33, 12.88)

(45, 14.97)

(69, 18.97)

and saw that it really looks like a logarithmic function. So, fitted y to
log(x), got y~7.4685*log(x)-13, with R^2=0.9965 (thank you R!). Extrapolated
back, and found that at conception, the fetus weighs -inf kilos. Not
surprising result, I must say. However, I was surprised to find that only
after five months of gestation, the embryo reaches the critical mass of 0
kilos. Science!

[1] [http://www.buzzle.com/articles/average-weight-for-
children-b...](http://www.buzzle.com/articles/average-weight-for-children-by-
age.html)

------
civilian
Their measure of complexity is Genome size. That's a very simple measure of
complexity.

Just a dumb example-- humans have a single gene for a protein in muscles. But
that single genes has multiple exons and depending on whether it's being
produced in heart, usual muscles, or soft-tissue muscle it's transcribed
differently. Most of the protein is re-used, but a couple of parts are swapped
out.

So we have genetic code being used in three different proteins. Our genome is
being efficient in size, yet it's increasing in complexity.

That being said, I have no idea how to measure complexity well.

------
ignostic
You know something is wrong when the complex and evolutionary trees of
"mammals" and "eukaryotes" are single points on a graph. If the geekbait
Moore's Law didn't tip you off, the paper is garbage.

------
api
I've suspected for a long time that the idea that life originated on Earth is
the last geocentrism.

