61 comments

[ 13.7 ms ] story [ 1271 ms ] thread
Can anyone explain why dogs (amongst others) age so much faster than humans? A 10 year old dog will be grey and have other visible aging signs, whilst we're still youthful. What is the difference? Are dogs cells dividing at a faster rate than ours, and if so why are they doing that? Presumably the answer gives us insight into the aging process, but I've not been able to find answers in some casual browsing.
Enquiry into the evolution of aging aims to explain why almost all living things weaken and die with age. There is not yet agreement in the scientific community on a single answer. The evolutionary origin of senescence remains a fundamental unsolved problem in biology.

http://en.wikipedia.org/wiki/Evolution_of_ageing

The biological mechanisms which regulate lifespan evolved several hundred million years ago.

edit: Regarding dogs: http://www.insidescience.org/content/large-dogs-age-faster-d...

The why is easy - like everything it is because dogs that age any slower than the average dog did not have any more offspring. The difficult question is the how question - how do humans and dogs differ in their ageing process. Anyone who can answer this will be more famous than Einstein.

A more interesting question is how do humans manage to age so much slower than chimps. This has occurred so recently in evolutionary history that it must involve only a few genes. Any process that is controlled by a few genes can, in theory at least, be a pharmaceutical target.

Are you sure humans age more slowly than chimps? I thought they basically live to the same age?
Oh man, that just made me realize my 9 year old dog doesn't have a lot of time left probably. It's weird, she doesn't seem to behave any differently than say 4-5 years ago, and still has lots of energy and zero health issues. So I just don't think of her as being old. According to these charts she's 55-60 in human years.
It's only a rule of thumb. Our Huskies (large dog) generally lived to be 15 to 17 years old. That's about 100 in human years according to the chart at the bottom of the article.
Depends on the dog, depends on the breed, depends on their health.

The problem with average life expectancy is that most dogs don't die of natural causes, they get put down. We would have a shorter average life span if we allowed people assisted suicide for those with terminal conditions, especially ones that drag on for years or decades. Think ALS, Alzheimers and Parkinson's, they can last twenty or thirty years. Often long past when a person would want to die for the benefit of themselves but also everyone around them.

We make that choice for our dogs. My in-laws put their dog down, he likely could have got another year but he was suffering and you don't torture things you love with forcing them to stay alive.

We humans are very badly designed.

A dog probably gets around eight active years or more, but we humans only have like three. When we are mature, fertile, energetic, without building up health problems.

And then we have six more dog years of being old.

Are you by chance in your early twenties?

The core message is that animal years map very badly to human years.

During the first twenty years, we are busy with development. The fertility part is gender specific, and lasts about 25 to 30 years in women and much longer in men. Conflating active years with fertility is a problematic idea. Maturity is a very fuzzy concept, but cortical development is commonly not considered complete until the mid-twenties. The variance in energy is probably higher compared across different individuals than across different age groups. Health problems also vary greatly from person to person, but it's fair to say that crossing 40 risk factors for everything go up dramatically.

How many active years humans get out of their life is subject to great individual variation. Some get zero. Others are highly productive for 60+ years. But I agree it's not enough - that's why we need transhuman advances in science. Less than a Guard of Terra, maybe more like a Space Marine ;)

I'm in late twenties.

The idea that I have to make all the important choices in the first half (second quarter even) of my life which is almost over saddens me.

Short fertility in women (which we cut in half with our clumsy society) is THE problem. With the exclusion of mismatches, which I shun, male fertility is effectively limited to the same age range too.

It depends a lot on attitude. If you consider procreation and family a big goal in your life, then you're right: the clock is always ticking. I'm almost 40 now, that ship has thoroughly sailed.

I don't agree that all the important choices happen during the first half though. Consider that for the first 1.5 decades you hardly make any of your own choices at all. So while the procreation thing is about halfway over at your age, in a lot of other ways you're just getting started.

If procreation and family is not a big goal in your life, then it ain't life. Because reproduction is a defining property of "life" if you think of it.

As I've added, it's actually a quarter. For women in modern society it's even less, close to 1/8 of their life.

After "the ship has sailed", no choices matter anymore. Surely, you may decompose faster or slower, rot for quite some time or go out with the bang. But it's confined to your own body now, which is definitely mortal.

>After "the ship has sailed", no choices matter anymore. Surely, you may decompose faster or slower, rot for quite some time or go out with the bang. But it's confined to your own body now, which is definitely mortal.

You're assuming the only way to influence the world is by spreading your genes. That's completely false.

I'm assuming that the only satisfying way to influense the world is one that includes spreading your genes.

And the age constaint is a huge problem here because it can ruin the whole thing even if I figure out everything else later on. You can fix many things later but not this. That's scary.

> I'm assuming that the only satisfying way to influense the world is one that includes spreading your genes.

We get that, but it's an assumption that depends on your personal value system and on what you personally consider satisfying. That's hardly something you can just project onto the general population.

A lot of people will agree with your basic assessment, however in this extreme form I'm afraid you're rapidly coming to a point where you don't see any value in humans once they have spawned their genes. And that's not how we as a civilization see things any more, and the understanding that we have value based on who we are (instead of how many offspring we have) has been part of the general social contract since at least the enlightenment era.

"That's hardly something you can just project onto the general population"

I didn't. However I think it is true for a big part of general population and they'll face a reality check soon enough. But I talk about myself mostly.

"I'm afraid you're rapidly coming to a point where you don't see any value in humans once they have spawned their genes"

It's a bit different. People who are still able to spawn their genes are unconditionally valuable. But people who can no longer spawn their genes are only conditionally valuable. They may be very valuable (take nobel laureates), but it's not given. Maybe not.

The problem is, people are only really fertile for a tiny part of their life. Increasingly tiny. That's a problem for us. That's my opinion.

> But people who can no longer spawn their genes are only conditionally valuable.

And that value is assigned conditionally by... you? It's your belief that the value of human life is restricted to its immediate usefulness?

> The problem is, people are only really fertile for a tiny part of their life. Increasingly tiny. That's a problem for us.

Again, I was not aware that we had a population crisis.

We're talking about my views anyway, why would you ask that over and over?

If you don't see this as a problem, you may just move along.

I was asking because I was fascinated and curious.
My views don't have to conform to whatever constraints you expect them to. I'm just telling you what I really think.
> My views don't have to conform to whatever constraints you expect them to.

That's why I asked about your views "over and over", because I wanted to find out how your value system works. There is no need to get testy. It's true that I disagree, but this discussion happened mostly because I wanted to find out more, not because I wanted to display your views in a misleading light. Peace.

I just failed to understand why you were surprised that in my views I assign value to people and not some external entity does.

The opposite will be actually weird.

(comment deleted)
> If procreation and family is not a big goal in your life, then it ain't life. [...] After "the ship has sailed", no choices matter anymore.

For your sake, I hope you'll change your view on this eventually. But I appreciate your honesty in expressing your belief that I should just kill myself right now.

It depends hugely on what value you assign to the human mind. If you believe that humans are "just" wildlife and mere existence is the highest achievable goal, you're likely to come to the conclusion that nothing matters but procreation.

But I highly doubt that you really believe this, because you're here, on HN, thinking about and debating matters that are far removed from the static archaic society whose values you ostensibly subscribe to.

There are a lot of people who think that human life is more than a mere bacteria-like existence, and that its value extends beyond our biological goals and limitations. Whether you like it or not, we have long since started to explore problem spaces that could simply never be addressed with mindless biological evolution. For a few thousand years now we are in the process of out-growing our original substrate. As a civilization we're engaged in a complex struggle to eventually grow beyond an existence that is defined only by the most basic biological needs.

If you can find it within yourself to identify with that struggle in some way, you may find that defining procreation as the ultimate end-all-be-all was the most bleak and unproductive premise you could possibly come up with.

"your belief that I should just kill myself right now"

My belief is that you don't have do anything, because it doesn't matter anymore. Might as well stay technically alive.

"For a few thousand years now we are in the process of out-growing our original substrate"

We're still not there. If we had uterine replicators, the problem we're discussing would be a non-issue.

But, we don't. So it's a huge issue. We have to stay alive, and we're all dead in less than 100 years. Therefore, we have to reproduce. Surely we also have other goals, but reproduction is a sanity check on those.

Maybe we can tear this chain apart one day, but we didn't yet.

> If we had uterine replicators, the problem we're discussing would be a non-issue. But, we don't. So it's a huge issue. We have to stay alive, and we're all dead in less than 100 years

How can you look at this world and come to the conclusion that it's essential - and indeed the sole reason for being here - for everyone to spawn offspring? Is there an underpopulation problem I'm not aware of? Is the human race in danger of dying out?

> My belief is that you don't have do anything, because it doesn't matter anymore. Might as well stay technically alive.

In the light of your answer above I can't square this logically. You're asserting that my life would suddenly become meaningful again if we had "uterine replicators"?

"Is there an underpopulation problem I'm not aware of?"

Actually there is. A lot of developed societies face shrinking population. And the population of young people capable of spawning offspring will decrease much faster.

And I'm not sure that undeveloped societies are capable of both "carrying the flag" and not falling into the same trap. They don't have a good record if you ask me.

"You're asserting that my life would suddenly become meaningful again if we had "uterine replicators"?"

Yes, because now you (or I) have choice to procreate. You may for some reason refuse to do it, but you can. Now, when you no longer have this choice, you're a "human minus procreation" which is less than "human".

> Yes, because now you (or I) have choice to procreate.

This is bizarre, because we're talking about the same mind, doing the same things for society (or not) - it's just that in one case testicles have a function and in the other they don't. So depending on the overall state of gonads in our civilization I'm worthless now - but if we didn't need gonads, my mind would suddenly start having a value?

That is truly and epically twisted.

> Now, when you no longer have this choice, you're a "human minus procreation" which is less than "human".

Well, to be labeled subhuman by you in this context feels almost like a compliment.

I'm not saying that you're worthless. I'm just not sure you're alive by strict standards. I'm not sure I will be - in fifteen years.

So now you think that I've "labeled" 1000 - 1 to be less than 1000? So much for math.

Even without passing on your own genes directly, you can:

1) help make sure those copies of your genes in others survive (help out relatives who did reproduce) - evolutionarily, this is equivalent to reproducing, if slightly attenuated;

and 2) have a lasting memetic impact.

And that's if you're focused only on the long term, which you seem to be - there's plenty more shorter term reasons to be alive.

Just to chase down this train of thought a little more: there are lots of ways to benefit your clan (and therefore some of your genes) without reproducing. Look at bees and termites, where the vast majority of them never reproduce, yet the queen is driven to produce them because they help the colony survive. That's selection too.

Or how about a gene that drives non-reproductive young males to be restless, jump on a horse and ride over the horizon on a whim. Sometimes they come back, say "There's buffalo over there!" and the whole tribe benefits. That's selected for too.

Sad thing is, I don't have a clan. I don't have a beehive, a community. So it seems that the only way for me to "keep the money in the bank" is reproduce physically.

That's why nuclear family is called nuclear. And today we often have "subnuclear" people without any strong bonds.

If I had a kind of clan, the situatiou would be different.

So if we take as given that you're going to be focused on the evolutionary component, if you can no longer reproduce then walk up your family tree until you find your closest relative with progeny.

http://en.wikipedia.org/wiki/Kin_selection#Hamilton.27s_rule

http://en.wikipedia.org/wiki/Inclusive_fitness

I'm not a walking set of genes. I'm a human being.

What if I don't feel that my "closest relative with progeny" is in any way related to me?

I don't care about inclusive fitness. Let the nature do that trick. I care about reproducing something resembling of myself. If my nearest genetic relatives don't resemble myself in any way, I don't care if they reproduce.

"I'm not a walking set of genes. I'm a human being."

Certainly. But then I'd say that a huge portion of what makes you you is not genetic at all, and like I said much earlier you can always pass on memes.

I can't reliably pass on memes because I don't have a clan. I'm a lone nation of one (well, two, anyway), and this nation is going to disappear once we die.

I can give memes to other unrelated people but I don't know whether they use those for good.

You don't know that your children will "use those for good" either. Focus on spreading memes that promote doing good, however you define "doing good".
I don't think that promoting doing good works. It seems that bad things are much easier to promote these days. I don't believe in it anymore.

Children are safe bet in that regards (if you failed - means you just passed your failureness to them, good)

"It seems that bad things are much easier to promote these days."

I don't see why that doesn't mean you should work harder at it. Maybe the marginal benefit is minimal, but if the marginal benefit of everything else is zero then it might still be the best option.

It's humiliating trying to walk thru the wall by fruitlees effort.
You have a culture that produced you. Maybe we can craft a cultural-selection story.
I don't happen to particularily like that culture. It's toxic for most part. There are some nice touches here and there, but I can't tie myself to it fully.
Come on now. There's the whole 'civilization' thing, and hospitals, and Bach, and Led Zeppelin, and eating with a fork... you can go on and on. Culture is more than politics.
The culture will go without me badly enough. I don't feel that I contribute to it in a meaningful way, even less that I had any say on how things were.
You're going to have a disasterous time if you discover you are infertile.

You might want to develop a different ideology to help you cope in that event.

The CD suggests that male fertility problems are not rare.

> Many couples struggle with infertility and seek help to become pregnant; however, it is often thought of as only a women’s condition. A CDC study analyzed data from the 2002 National Survey of Family Growth and found that 7.5% of all sexually experienced men younger than age 45 reported seeing a fertility doctor during their lifetime—this equals 3.3–4.7 million men. Of men who sought help, 18% were diagnosed with a male-related infertility problem, including sperm or semen problems (14%) and varicocele (6%).

http://www.cdc.gov/reproductivehealth/infertility/#a

Most of that is accurate, but careful you don't drift into group selection, which (as I understand it) isn't well supported by the available evidence. To be selected for, a trait needs to differentially increase the likelihood that genes for that trait are passed on, so there needs to be a sufficiently close relationship that the person being benefited is likely to share the gene responsible for the help (or greater effectiveness of the help, or...). Of course, there is another leap from "X causes a trait to be selected for" to "we should individually be valuing X", but guard-of-terra seems to be thinking in those terms to begin with (and others have questioned that point).
Well, other than bees and termites I guess? What is that but group selection.
Due to inbreeding, termites are more closely related to their siblings than to their children. You can approximate it as group selection, but it's not a separate thing that's going on - it can be reduced to selection on individual genes.
>We have to stay alive, and we're all dead in less than 100 years. Therefore, we have to reproduce. Surely we also have other goals, but reproduction is a sanity check on those.

You're discounting the value of information that people can leave, separate to their DNA chain. A great many scientists, artists, philosophers, etc. bore no children. They still expressed a change in the behaviors, ideas, and lives of a great many people after them.

Actually, one might argue they are, by and large, more effective at continuity of their own goals. How many children have you seen carry on the worldviews and goals of their parents? Even throughout history?

Yes, we need SOMEONE to reproduce or there won't be anyone to read the damned work. But, the work is still there, unto itself, after it's author has passed away.

tl;dr: The production of children is not the only way affect the Universe after your death as a human.

I personally do not trust that kind of "SOMEONE" we have that they'll produce and nourish the offspring capable of "carrying the banner".

And I can't associate with them and their offspring.

That's a valid pursuit, and I think it noble of you. Your associations are your own, and I don't intend to suggest they be any particular way at all.

Still, your point doesn't take away from those non-SOMEONE's that do not bear children, and the net impact they have left on humanity and the Universe. I can't believe that Leonardo DaVinci, Michelangelo, and so many other contributors to the works of humanity that had no children were "lives wasted" for their lack of reproduction.

Udo said this:

> But I highly doubt that you really believe this, because you're here, on HN, thinking about and debating matters that are far removed from the static archaic society whose values you ostensibly subscribe to.

You didn't reply to it initially; I was hoping to see your thoughts on that point.

No, I don't subscribe to the values of a "static archaic society". I think those values are self-defeating bullshit.

But I think we haven't got a new stable set of values either. We're literally doing the same thing to demographics as we do with oil - eating away future generations' prospects. But the same people who shun oil overusage and pollution praise demographic "overmining" and "waste".

However I really believe that I would feel dead when I strike 50 without descendants. And that's a pretty likely outcome.

>There are a lot of people who think that human life is more than a mere bacteria-like existence, and that its value extends beyond our biological goals and limitations. Whether you like it or not, we have long since started to explore problem spaces that could simply never be addressed with mindless biological evolution. For a few thousand years now we are in the process of out-growing our original substrate. As a civilization we're engaged in a complex struggle to eventually grow beyond an existence that is defined only by the most basic biological needs.

This is very well put. The 'process of out-growing our original substrate' is an interesting way to phrase advanced human growth, and one that resonates with me. I don't think we're alone in doing so (as far as life is concerned), and think we are more like our bacterial forebearers than our collective egos would care to admit, but I couldn't agree more that this is what we are doing.

Seems right; but I can't help thinking all we do that is not related to the physical is, by definition, imaginary. We THINK we're doing things, but its all fantasy stuff - art, math, philosophy. Imagine a different biology of intelligent beings - maybe an amoebic colony-mass of semi-intelligent cells that create a group brain. What would their philosophy look like? Would they have trade or commerce or families or anything we would recognize? I think No.

But they have 'left their substrate' too. Yet there's no common ground with us. That means, most of what we do 'beyond our biological goals' is in fact still rooted in our biology.

Very interesting. I'm going to have to ponder on that one.

I agree that goals 'beyond our biology' are, quite basically, rooted IN THAT biology. We can never trust our perception to be anything other than a reflection of that biology, so I see your point.

>Would they have trade or commerce or families or anything we would recognize? using different language, maybe. They WOULD have resource transmission and interactions, methods of managing scarcity, and methods of categorizing and identifying individual nodes in their system.

Its a fun game to imagine 10 commandments for alien races. E.g. Thou Shalt Kill thy Father, Mother and CoProgenitors for a race that eats their ancestors to process their neurological tissue and preserve their knowledge and personalities.
My vet actually had the 15, 10, 4, 4... etc chart on the wall.

I think 7 came because at the end of the dog's natural life you could get a rough estimate using the rule of 7 because it averaged out.

OK, a long read, but at the end it seems that she was actually even older than the equivalent of 200 human years? :)
The concept of 'dog years' has always interested me. I recently quipped to some friends that if there's 7 dog years in a human year, there's 2^y computer years in a human year; so a 6 year old computer is 64 in computer years.
> Puberty range in most women and bitches

At first I was offended and then I was 'Oohh...'