

Body mass is correlated with lifespan - colinprince
http://www.npr.org/blogs/krulwich/2013/01/22/169976655/nature-has-a-formula-that-tells-us-when-its-time-to-die

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jmilloy
As usual, read the paper instead [0]. It's short, clear, and easy to read. In
particular, it applies _only_ to plants, so the article's musings about
jellyfish and elephants is off the mark and even addressed in the paper [1].
So is the irrelevant discussion of "pulse", which is oddly supported with
video that is just played forward and backward.

The paper just claims to support some known, quantifiable correlations with
some data. The correlations pertain to mortality _rates_ and birth _rates_ ,
and certainly suggests no formula for when to die, or causation of any sort
for that matter. E.g, is it that bigger plants die less often, or that plants
that die less often can get bigger? Does it matter?

[0] <http://www.pnas.org/content/104/40/15777.full>

[1] "Whereas the action of selective processes on animal lifespan cannot
extend through their entire lifespan because many lose reproductive capacity
with age, this is not the case in plants, which generally remain reproductive
throughout their lifespan, suggesting that lifespan could be under greater
selective pressure in plants."

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redwood
Perhaps it's better to suggest that plants which grow into their own
foundations eventually reach a limit whereby it's hard for the plant to
continue getting the nutrients it needs without being essentially blocked by
its prior scaffolding? Bigger plants are the ones that reach this limit later,
e.g. have evolved ways of using prior root systems/trunks to their benefit
overtime.

Plants _can_ essentially live forever through cloning, where the plant lays
new roots and isn't stuck on its former shell.

On the other hand stressed plants go to seed (a good evolutionary move) and
statistically no plant lives forever in the wild, with fires and etc, so
perhaps this data is more of a testament to how fragile a plant is... e.g. how
easily it's killed. It makes sense that smaller = more fragile, more easily
burnt/frozen to death, etc.

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AngryParsley
The last graph amuses me:
[http://media.npr.org/assets/img/2013/01/22/graph_custom-3939...](http://media.npr.org/assets/img/2013/01/22/graph_custom-3939b09513b4668a3e8aff03cd481e72683f1012-s4.jpg)

Even on a log-log graph, the data looks like a shotgun spread. Species of
similar mass have lifetimes that vary by up to a factor of 1,000. Species with
similar life-spans differ in mass by up to a factor of a trillion.

~~~
bernardom
This. I see how the three clusters (plankton, trees, and everything else) are
arranged in a way suggesting a linear relationship, but within the clusters?
Nothing.

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Irregardless
The title is pure linkbait, which is surprising for NPR. I guess that's the
only way to get more clicks when the entire article boils down to "Large
plants/animals live longer, on average (except humans)". Thanks, we hadn't
already noticed.

A formula that "tells us when it's time to die" would imply some sort of
prediction about individuals, which they admit is not the case at all. _That_
would actually be interesting.

~~~
hemancuso
Visual inspection also suggests a rather low R^2 on that regression. It looks
much more like a loose correlation than a formula to me.

~~~
Irregardless
Good point, I'd only glanced at the chart.

Looks like the trees along the right have a half-life range of <10,000 to
>1,000,000, even with nearly identical individual mass.

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eduardordm
Well, I don't think the author understood the paper.

Make sure you correctly read a paper before spreading wrong conclusions. The
article is about the relationship between death, birth and mass (which are
obviously connected, the paper is about that relationship). Time is just the
scope there.

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xerula
There is nothing new about the observation that body mass is correlated with
lifespan, at the level of species - why should we be at all surprised that the
correlation is described by some power law? There are compelling metabolic
explanations for these patterns going back more than a century. What really
excites modern biologists – and what the article completely fails to discuss
(even to the point of claiming "this rule seems to govern all life") – are the
numerous and dramatic _exceptions_ to the rule: naked role rats, tardigrades,
certain cnidarians ("immortal" jellyfish & hydra) and planarians, various
lichens... In some of these cases, metabolic rate is divorced from body size
through a well-characterized, indefinite hibernation 'mode', but more
efficient DNA protection, repair and telomere length preservation systems are
also important. And there is a substantial literature that explains unusually
prolonged life-cycles using Evolutionary Stable Strategy modeling. All of
which provide useful perspectives in aging research. Much more interesting
would have been an article about how these violations of nature's "death
formula" tell us how we might avoid death.

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tocomment
What about tortoises? Jellyfish?

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JCraig
Tortoises were the first to come to mind for me. Later in the article, it does
state that it's not just size but metabolism that figures into this
correlation.

That being said. The article states that this relationship governs "all life"
but only gives data for plants. Even there, "some variation, but not a lot" is
an extremely generous representation. For the same mass, a difference in
mortality rate could be 10^3 or more if I'm reading the graph correctly. While
the relationship might roughly follow a trend, I wouldn't call that "not a
lot" of variation. It's interesting, but I think the authors are overselling
the relationship.

~~~
travisp
Further, it can't _just_ be metabolism. It is unlikely that it's simply the
metabolism of some tortoises, lobsters, and hydras that causes them to not
actually age. It's not that they just have extra long lifespans, their death
rates do not increase with age.

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brenfrow
My question is if we all get 1.5 billion heart beats. What if I run long
distance and do alot of cardio and get my resting heartbeat down to 45 beats a
minute. Will I on average out live someone who has a resting pulse of 70?

~~~
nagrom
I would imagine that you use up some of those 'extra' resting heartbeats by
doing all that cardio and long distance running, no?

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leeoniya
<http://en.wikipedia.org/wiki/Telomerase#Aging>

~~~
travisp
Are you suggesting telomeres or telomerase activity correlates with the size
of the species? It's unclear what exactly is the role of telomeres in aging.
Your article says "it is currently unknown to what extent telomere erosion
contributes to the normal aging process". It is a major hypothesis, but
there's a lot we don't know about it.

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return0
This works for plants. Plants have a very (very) stable environment.

~~~
redwood
Not when the raging forest fire comes :)

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return0
Well it's not like they pack their bags and run away...

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septerr
Did anyone else feel like the gifs were overused?

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brazzy
Chuck Norris tells nature when it's time to die.

