/ God and science and life and death
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?
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).
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.
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
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.
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.
I think you will find death evolved very shortly after life.
Tell that to the lobsters.
Al - the answers are out there...
Parrots don't have a lot of natural predators, whereas ducks do.
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.
OK then, but do tortoises taste shit?
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.
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.
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.
> 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!
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.
No-one said it was fair!
And it's all relative.
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."
You sure you didn't mean to post that on the 'Quacks on radio 4' thread?
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