/ God and science and life and death

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Al Evans on 04 Oct 2012
There is all this research going into how life evolved and how we as humans did, but what about death, how did that evolve?
Why for instance do we get lucky with three score year and ten, much the same as a parrot, but ducks, about the same size as a parrot and similar species only get ten years. And why is the longest living thing on the planet a plant, or if you are talking animals a tortoise, Shouldn't scientists be looking into that too, I don't just mean trying to extend human life, but why all creatures have the lifetimes they do?
Hardonicus - on 04 Oct 2012
In reply to Al Evans: They are. But it's complicated man!
mack - on 04 Oct 2012
In reply to Al Evans:

I highly recommend the book 'Power, Sex and Suicide - Mitochondria and the meaning of life' by Nick Lane.

He puts forward some good explanations of life and death.(unless one is a non-believer in evolution).
tlm - on 04 Oct 2012
In reply to Al Evans:

here you go Al - google is your friend.

http://longevity-science.org/Evolution.htm
gethin_allen on 04 Oct 2012
In reply to Al Evans:
The finite number of heart beats theory is a good if not very scientific one.
you have a finite number hence if you have high rate you die sooner.
mkean - on 04 Oct 2012
In reply to Al Evans:
It is complicated ;-)

Lots of things alter how long an animal will live, one interesting one I saw recently was that lots of animals that are thought to navigate using the earths magnetic field don't live as long as other animals. As the chemicals involved produce harmful radicals.

http://www.ks.uiuc.edu/Research/cryptochrome/ is a starting point
cb294 - on 04 Oct 2012
In reply to Al Evans:

Hi,

that has been studied extensively, and the theory behind it is pretty much understood. This makes it less of a discussion point, unless some extreme example is found, e.g. the recently discovered Malegasy chameleons that never meet the next generation: Hatch, mate, lay eggs, die, (wait through dry season), hatch,.... Essentially, one generation of animals is born every year that lives for about three months, and for 9 months you will only find eggs.

To be brief, life span is over evolutionary time selected to maximise the number of ones offspring in the gene pool of the later generations. This is easy to see in extreme cases like salmon. Even for an adult salmon, the chances of making the trip to sea and back for a second time are marginal. It is therefore much more efficient to allocate all resources into making egg or sperm, and die, rather than survive mating season and likely be eaten before getting a second shot.

Female Orcas on the other hand are long lived, livig for several decades even after menopause when they cannot have offspring of their own anymore. Here it was shown that there is a strong effect on the survival of their sons, presumably through better hunting success of larger pods. Living longer rewards the individual with more grandchildren, and is thus fixed in the population.

This of course comes on top of an older evolutionary commitment towards sexual reproduction. We are not immortal but only our germline is, which e.g. helps with getting rid of mutational load.

Cheers,

CB
Jon Stewart - on 04 Oct 2012
In reply to Al Evans: Really interesting question. There must be loads out there on it, but it seems to me the best way of looking at it is (as for all questions about biological life really) is from the genes' point of view - as Dawkins explains brilliantly.

So genes want to reproduce themselves, and they clump together in genomes to create all kinds of amazing biological vehicles to carry them around and do the reproducing. Given that the gene's only 'aim' is replication, it doesn't help for one copy to be around for ever, or indeed for ages. If the vehicles for replication lasted for ages, on the one hand they'd be able to do lots of replication, and might be handy to have around to make sure that their young survived, but on the other, they'd all be competing for resources and a proportion of them would end up getting killed off by each other, defeating the point of the whole exercise. Also, as environmental factors change, the replication machines have to adapt, so a decent 'turnover' is needed to keep them 'up to date'.

Given all of this, for whatever type of replication machine the collaborating bunch of genes is using, there'll be an optimum lifespan - so presumably that's about 40ish years for humans (or whatever lifespan we have 'naturally'), and much less for flies. So I reckon it's probably spot on to think about how death evolved, rather than it just being an unwanted consequence of life.

That's my understanding anyhow, I'm sure there's a lot more to it. But it does seem to me that if it was useful from our genes' point of view to last forever, we would. I don't see why we couldn't regenerate constantly if that was advantageous.
In reply to Al Evans:
> There is all this research going into how life evolved and how we as humans did, but what about death, how did that evolve?
>

I think you will find death evolved very shortly after life.


Chris
Dave Garnett - on 04 Oct 2012
In reply to Chris Craggs:

Tell that to the lobsters.
Al Evans on 04 Oct 2012
In reply to Jon Stewart: But none of the above explains why Parrots live to be 70 and Ducks only live to be 10. Or even starts to explain the vagaries of human lifetimes given all other things being equal.
tlm - on 04 Oct 2012
In reply to Al Evans:
> (In reply to Jon Stewart) But none of the above explains why Parrots live to be 70 and Ducks only live to be 10. Or even starts to explain the vagaries of human lifetimes given all other things being equal.

Al - the answers are out there...

Parrots don't have a lot of natural predators, whereas ducks do.

http://sciencefocus.com/qa/why-are-parrots-so-long-lived
Jon Stewart - on 04 Oct 2012
In reply to Al Evans: It doesn't explain specific cases but it explains why each creature has a certain lifetime.

For people, it takes a while to reach sexual maturity, quite a lot of effort is needed to up the chances of survival of each offspring, so we'll definitely be up in the 10s of years rather than single figures. I think the reason it's more like 50 than 5000 years is for the reasons above. I don't think it would be possible to explain why 50 rather than 100 (presuming no medicine) - both would probably work OK from the genes' perspective, so at a certain level of detail it'll boil down to "that's how it turned out". But there are good reasons human lifespan isn't 10 or 1000 years.
Al Evans on 04 Oct 2012
In reply to tlm: Well I've read that and it doesn't even begin to explain why ducks have such a short life compared to parrots, most ducks are well fed and have few predators, I would suggest better fed than parrots and with fewer predators which makes a nonsense of that article.
gcandlin - on 04 Oct 2012
In reply to Al Evans: maybe now they are but over the evolutionary time scale that might not have been the case
In reply to Al Evans: I thought both parrots and ducks have similar lifespans in the wild but parrots in captivity are longer due to the environment.

Jon Stewart - on 04 Oct 2012
In reply to Al Evans: I reckon proper ducks (as opposed to ones living in a human-made environment) have loads of predators. They do taste nice after all.
Al Evans on 04 Oct 2012
In reply to Jon Stewart:
> (In reply to Al Evans) I reckon proper ducks (as opposed to ones living in a human-made environment) have loads of predators. They do taste nice after all.

OK then, but do tortoises taste shit?
mkean - on 04 Oct 2012
In reply to Al Evans:
Tortoises are pretty tricky things to open, plus they have very slow metabolisms so don't suffer from the sort of cellular stresses that faster moving creatures do.
Mr Powly - on 04 Oct 2012
In reply to Al Evans:

Assuming the difference in life expectancy of ducks and parrots is correct I imagine it's to do with their relative fecundity and investment in their offspring.

Ducks tend to have large clutches of offspring once (or maybe more) each year, several of which might die. Judging from their longer lifespan I would expect parrots reproduce less regularly producing only one or two chicks and looking after them more carefully. It's just different ways of doing things. Condors and albatrosses both live up to 70 years, about the same natural lifespan as humans, and also have chicks only once every few years, singly or in pairs, and the chicks take a couple of years to mature and require a lot of looking after by their parents.
ads.ukclimbing.com
Mr Powly - on 04 Oct 2012
In reply to Al Evans:

Also why do people say things like 'shouldn't scientists be looking into this thing I have just thought of' without stopping to think that maybe someone who thinks about such things for a career just might have thought of them already.
Jon Stewart - on 04 Oct 2012
In reply to Al Evans:
> (In reply to Jon Stewart)
> [...]
>
> OK then, but do tortoises taste shit?

We don't farm them for food so I'm guessing yes. But they're probably a delicacy somewhere!
owlart - on 04 Oct 2012
In reply to Jon Stewart: According to QI (so it must be true!), they taste do delicious that it was almost impossible to bring one back to study as they would always be eaten on the return journey!
Sebastian Fontleroy - on 04 Oct 2012
In reply to Al Evans:

I recommend you read 'The Selfish Gene' by Richard Dawkins. He puts forward an interesting theory as to how we can lengthen our lifetime by putting off reproduction till later in life.
Bulls Crack - on 04 Oct 2012
In reply to Al Evans:

No-one said it was fair!

And it's all relative.
tlm - on 07 Oct 2012
In reply to Al Evans:

Al! Don't you look stuff up?

"Worldwide, ducks have many predators. Ducklings are particularly vulnerable, since their inability to fly makes them easy prey not only for predatory birds but also large fish like pike, crocodilians, and other aquatic hunters, including fish-eating birds such as herons. Ducks' nests are raided by land-based predators, and brooding females may be caught unaware on the nest by mammals, such as foxes, or large birds, such as hawks or eagles.
Adult ducks are fast fliers, but may be caught on the water by large aquatic predators including big fish such as the North American muskie and the European pike. In flight, ducks are safe from all but a few predators such as humans and the Peregrine Falcon, which regularly uses its speed and strength to catch ducks."
john arran - on 07 Oct 2012
In reply to tlm:

You sure you didn't mean to post that on the 'Quacks on radio 4' thread?

;-)

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