Comments on: A life in the trees is a longer one http://blogs.discovermagazine.com/notrocketscience/2010/02/22/a-life-in-the-trees-is-a-longer-one/ Mon, 26 Nov 2012 12:00:51 +0000 hourly 1 http://wordpress.org/?v=3.4.2 By: The Mad LOLScientist, FCD http://blogs.discovermagazine.com/notrocketscience/2010/02/22/a-life-in-the-trees-is-a-longer-one/#comment-6585 The Mad LOLScientist, FCD Tue, 02 Mar 2010 08:03:25 +0000 http://blogs.discovermagazine.com/notrocketscience/2010/02/22/a-life-in-the-trees-is-a-longer-one/#comment-6585 ROFLmeow! Love your "assortment of tree-dwelling mammals"! =^..^= ROFLmeow! Love your “assortment of tree-dwelling mammals”!
=^..^=

]]> By: rich lawler http://blogs.discovermagazine.com/notrocketscience/2010/02/22/a-life-in-the-trees-is-a-longer-one/#comment-6584 rich lawler Thu, 25 Feb 2010 21:09:31 +0000 http://blogs.discovermagazine.com/notrocketscience/2010/02/22/a-life-in-the-trees-is-a-longer-one/#comment-6584 I'm not an expert on this topic but I happen to recall that the evolution of senescence is a theoretically slippery issue. I'm not doubting that there is a relationship between life in the trees and longevity, but demonstrating this in the context of the evolution of senescence requires something more than thinking about extrinsic mortality (which the authors refer to in the abstract and text), it requires a consideration of age-dependent extrinsic mortality. GC Williams main prediction that "extra morality" will cause senescence to evolve more quickly is imprecise (as shown most recently by Hal Caswell in a 2007 letter in Trends Ecol Evol), since the selection gradients acting on age-specific mortality (which shape the pattern of senescence) are unaffected by extrinsic mortality that is not age-specific. While the strength of selection decreases with age, the question is whether additional extrinsic mortality will cause the strength of selection to decrease even quicker (i.e., resulting in increased senescence)--something which Caswell (and Peter Abrams 1993 in Evolution) showed to be wrong. More to the point, increased "extrinsic mortality" across all age classes doesn't influence the evolution of senescence in a straightforward manner, but age-dependent extrinsic mortality does. In the future, it would be interesting to look at how mortality rates change with age, and how these age-specific rates are correlated with arboreality. I’m not an expert on this topic but I happen to recall that the evolution of senescence is a theoretically slippery issue. I’m not doubting that there is a relationship between life in the trees and longevity, but demonstrating this in the context of the evolution of senescence requires something more than thinking about extrinsic mortality (which the authors refer to in the abstract and text), it requires a consideration of age-dependent extrinsic mortality. GC Williams main prediction that “extra morality” will cause senescence to evolve more quickly is imprecise (as shown most recently by Hal Caswell in a 2007 letter in Trends Ecol Evol), since the selection gradients acting on age-specific mortality (which shape the pattern of senescence) are unaffected by extrinsic mortality that is not age-specific. While the strength of selection decreases with age, the question is whether additional extrinsic mortality will cause the strength of selection to decrease even quicker (i.e., resulting in increased senescence)–something which Caswell (and Peter Abrams 1993 in Evolution) showed to be wrong. More to the point, increased “extrinsic mortality” across all age classes doesn’t influence the evolution of senescence in a straightforward manner, but age-dependent extrinsic mortality does. In the future, it would be interesting to look at how mortality rates change with age, and how these age-specific rates are correlated with arboreality.

]]> By: Carrie@MaineCoonCatNation http://blogs.discovermagazine.com/notrocketscience/2010/02/22/a-life-in-the-trees-is-a-longer-one/#comment-6583 Carrie@MaineCoonCatNation Wed, 24 Feb 2010 02:00:21 +0000 http://blogs.discovermagazine.com/notrocketscience/2010/02/22/a-life-in-the-trees-is-a-longer-one/#comment-6583 This is so interesting. In the small city where I grew up there always gray squirrels darting in the street. I wonder how long they would live, as a group, without becoming roadkill? This is so interesting. In the small city where I grew up there always gray squirrels darting in the street. I wonder how long they would live, as a group, without becoming roadkill?

]]> By: Nathan Myers http://blogs.discovermagazine.com/notrocketscience/2010/02/22/a-life-in-the-trees-is-a-longer-one/#comment-6582 Nathan Myers Tue, 23 Feb 2010 21:36:06 +0000 http://blogs.discovermagazine.com/notrocketscience/2010/02/22/a-life-in-the-trees-is-a-longer-one/#comment-6582 Humans was my first guess, but I couldn't get the units to work out. (I can't get the PDF.) The ordinate, then, is log base 10 of grams, and the abscissa is log base 10 of months. I notice that the terrestrials appear to group along lines paralleling the main regression, below it. Do they share a common, particularly risky, environment? I suppose particular risks of juvenile mortality would throw off the trends. Humans was my first guess, but I couldn’t get the units to work out. (I can’t get the PDF.) The ordinate, then, is log base 10 of grams, and the abscissa is log base 10 of months.
I notice that the terrestrials appear to group along lines paralleling the main regression, below it. Do they share a common, particularly risky, environment? I suppose particular risks of juvenile mortality would throw off the trends.

]]> By: Ed Yong http://blogs.discovermagazine.com/notrocketscience/2010/02/22/a-life-in-the-trees-is-a-longer-one/#comment-6581 Ed Yong Tue, 23 Feb 2010 14:52:01 +0000 http://blogs.discovermagazine.com/notrocketscience/2010/02/22/a-life-in-the-trees-is-a-longer-one/#comment-6581 I asked Scott. <blockquote>That's humans! You can see the same datapoint in Fig 4. The numbers are 60.2 kg and 1469 months, or 122.4 years. We're the largest residual in this comparison. There are a few primates that are not far behind us though - Cebus, Hylobates, and Leontopithecus, for example. Hope that helps.</blockquote> Cebus = capuchins; Hylobates = gibbons; Leontopithecus = lion tamarins. I asked Scott.

That’s humans! You can see the same datapoint in Fig 4. The numbers are 60.2 kg and 1469 months, or 122.4 years. We’re the largest residual in this comparison. There are a few primates that are not far behind us though – Cebus, Hylobates, and Leontopithecus, for example. Hope that helps.

Cebus = capuchins; Hylobates = gibbons; Leontopithecus = lion tamarins.

]]> By: Nathan Myers http://blogs.discovermagazine.com/notrocketscience/2010/02/22/a-life-in-the-trees-is-a-longer-one/#comment-6580 Nathan Myers Tue, 23 Feb 2010 08:26:21 +0000 http://blogs.discovermagazine.com/notrocketscience/2010/02/22/a-life-in-the-trees-is-a-longer-one/#comment-6580 If it's the natural log, that point at the top of the graph is something that lives 24 years, and masses 120 kg or pounds; a chimpanzee? If it’s the natural log, that point at the top of the graph is something that lives 24 years, and masses 120 kg or pounds; a chimpanzee?

]]> By: Brian Schmidt http://blogs.discovermagazine.com/notrocketscience/2010/02/22/a-life-in-the-trees-is-a-longer-one/#comment-6579 Brian Schmidt Tue, 23 Feb 2010 06:32:51 +0000 http://blogs.discovermagazine.com/notrocketscience/2010/02/22/a-life-in-the-trees-is-a-longer-one/#comment-6579 I can only read the abstract - is it typical longevity records or maximum longevity records being discussed? If it's the former, the issue may be niche selection rather than aging. It makes sense that a species that chooses a defense-maximizing niche, like living in trees, flying, being cryptic, or developing body armor, will live longer than another species that occupies a different kind of evolutionary niche, like maximizing growth rates or litter size. I can only read the abstract – is it typical longevity records or maximum longevity records being discussed? If it’s the former, the issue may be niche selection rather than aging. It makes sense that a species that chooses a defense-maximizing niche, like living in trees, flying, being cryptic, or developing body armor, will live longer than another species that occupies a different kind of evolutionary niche, like maximizing growth rates or litter size.

]]> By: Oliver C http://blogs.discovermagazine.com/notrocketscience/2010/02/22/a-life-in-the-trees-is-a-longer-one/#comment-6578 Oliver C Tue, 23 Feb 2010 03:47:09 +0000 http://blogs.discovermagazine.com/notrocketscience/2010/02/22/a-life-in-the-trees-is-a-longer-one/#comment-6578 Concerning comment #4 by Gruner, it looks like the authors are currently exploring just that hypothesis: "The team is now setting its sights on burrowing mammals, to see if life underground also reduces risk and so ultimately extends the lifespans of those species." <a href="http://www.newscientist.com/article/dn18557-the-secret-of-long-life-is-up-in-the-trees.html" rel="nofollow">http://www.newscientist.com/article/dn18557-the-secret-of-long-life-is-up-in-the-trees.html</a> Concerning comment #4 by Gruner, it looks like the authors are currently exploring just that hypothesis:
“The team is now setting its sights on burrowing mammals, to see if life underground also reduces risk and so ultimately extends the lifespans of those species.”
http://www.newscientist.com/article/dn18557-the-secret-of-long-life-is-up-in-the-trees.html

]]> By: M Gruner http://blogs.discovermagazine.com/notrocketscience/2010/02/22/a-life-in-the-trees-is-a-longer-one/#comment-6577 M Gruner Tue, 23 Feb 2010 00:24:04 +0000 http://blogs.discovermagazine.com/notrocketscience/2010/02/22/a-life-in-the-trees-is-a-longer-one/#comment-6577 The African naked mole rat may be a supporting case for this hypothesis. Living underground and being eusocial they have incredibly long lives for a mammal their size. According to Wikipedia the naked mole rat is the longest lived rodent (reaching up to 28 years) compared to the African Pygmy Mouse which squeaks by at 2 yrs. The African naked mole rat may be a supporting case for this hypothesis. Living underground and being eusocial they have incredibly long lives for a mammal their size. According to Wikipedia the naked mole rat is the longest lived rodent (reaching up to 28 years) compared to the African Pygmy Mouse which squeaks by at 2 yrs.

]]> By: Matt http://blogs.discovermagazine.com/notrocketscience/2010/02/22/a-life-in-the-trees-is-a-longer-one/#comment-6576 Matt Mon, 22 Feb 2010 22:42:55 +0000 http://blogs.discovermagazine.com/notrocketscience/2010/02/22/a-life-in-the-trees-is-a-longer-one/#comment-6576 Isn't it pretty risky to spend your life where a single mistep drops you dozens of body lengths to the ground? Isn’t it pretty risky to spend your life where a single mistep drops you dozens of body lengths to the ground?

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