Wednesday 23 June 2021

Age

Like Hanno and his fellow immortals in Poul Anderson's The Boat Of A Million Years, Lazarus Long in Robert Heinlein's Methuselah's Children is an unaging mutant so is it just a coincidence that he is born in an early generation of a group that is being bred for longevity? Why do organisms age and to different ages?

"Why do hummingbirds live till they are ten, rockfish till they are two hundred, bristlecone pines till they are thousands of years old, and octopuses till they are two?"
-Peter Godfrey-Smith, Other Minds: The Octopus and the Evolution of Intelligent Life (London, 2018), 7, p. 164.
 
Godfrey-Smith summarizes two theories of aging. Because these theories are relevant to sf by Heinlein, Anderson, Blish and Niven, I will try to paraphrase them here.
 
Peter Medawar's Argument
Any animals that did not die of old age would eventually die from some external cause. A mutation that was harmful only at an advanced age would not be selected out because most animals would die from other causes before reaching that advanced age. Therefore, the mutated genes would become common so that individuals that did reach an advanced age would then die of "old age."
 
George Williams' Similar Argument
Mutations that are beneficial early in life but harmful later in life will be naturally selected until an entire population bears the mutated genes and every individual who survives long enough then suffers from the harmful later effects.

According to these theories, Lazarus Long and Hanno etc are individuals born without the gene that is harmful later in life.

I have also encountered the theory that, in primitive society, when nearly everyone died young from external causes, it was not yet known that there was any death from old age so it was thought that immortality was the natural state that had been lost with an expulsion from Eden. Of the sf works mentioned here, this theory is most relevant to Larry Niven's Protector.

16 comments:

Sean M. Brooks said...

Kaor, Paul!

I am not sure the last paragraph is correct, at least for humans. Even the most primitive societies had some "elders" who lived to what would be considered old age by them. Even it was only to age 45 or 50.

Ad astra! Sean

paulshackley2017@gmail.com said...

Sean,

Yes. Old age was rare, respected and revered.

Paul.

Sean M. Brooks said...

Kaor, Paul!

In most, not all cultures. The Indians of "Men of Peace" in THE BOAT OF A MILLION YEARS disdained age.

Ad astra! Sean

S.M. Stirling said...

Some people have always lived to the biological limit, the 80-100 range. And high infant mortality skews the averages downward; if the average lifespan is 36, that doesn’t mean a 20-year-old has only 15 years left. It usually means a lot of infants don’ make it to 20, but the 20-something has a fair chance of ‘three score and ten’.

Sean M. Brooks said...

Kaor, Mr. Stirling!

While I agree, I have strong doubts that more than a very few lived that long in the Old and New Stone Ages. And before modern medicine and public hygiene, cites were sinkholes of pestilence, plague, and disease. Most people did well if they managed to live to age 50 before about 1900.

Ad astra! Sean

S.M. Stirling said...

The median age of death for adults in colonial New England in 1700 was 71, for example. (It was in the 50’s for Virginia at that time; the place was very unhealthy.)

Hunter-gatherers tend to be well-nourished and have low disease loads compared to farmers, if they’re not exposed to outside illnesses; they don’t work nearly as hard, either.

paulshackley2017@gmail.com said...

71 is high for a median age.

Sean M. Brooks said...

Kaor, Mr. Stirling!

You raised valid points I have to agree with. Esp. since I had not known Colonial New England had such a high median life span.

And I should have remembered the points you made about Stone Age hunter/gatherers. Probably what really depressed their average life span was the risk of violent death at the hands of other hunter/gatherer bands.

Ad astra! Sean

S.M. Stirling said...

Paul: median age at death.

Sean : the evidence indicates that something over half of adult male deaths were due to violence, with the female proportion being about half that - still very high. That ‘s quite uniform for pre-State cultures.

S.M. Stirling said...

Cities were very unhealthy but most people didn’ live in cities.

no: one reason English people were willing to try colonizing extremely dangerous p,aces was that it usually wasn’t any more dangerous than moving to London, which had 3-5 burials for every baptism, even in non-plague years. And 10% of every generation of English people did move to London.

paulshackley2017@gmail.com said...

That still seems a high median age at death unless I am misunderstanding "median." (I am hopeless at maths.)

Sean M. Brooks said...

Kaor, Mr. Stirling!

And so many pre-state males and women in hunter/gatherer bands died violently for reasons like clashes over hunting grounds, raids for women, or just plain malevolence? I can believe that!

Interesting, I don't think I ever came across that idea yet, that colonies were no more dangerous for English people to settle or move to, than was the case for London, with its monstrous average number or deaths per annum.

Ad astra! Sean

S.M. Stirling said...

Sean: also, in early- modern England you had to have a certain degree of economic independence to marry and have a family. Most people (men and women) didn’t marry until a good 10 years after puberty for just that reason. From 5% to 20% didn’t marry at all and died childless. It was worth a good deal of risk to establish a competency and your own household. In the American colonies where land and food were cheap, nearly everyone married, they did so 8 or so years younger than their English kin, and they had an average of 6 children rather than 3.

People in England would have done that if they could; they just couldn’t afford it.

It was like having all the firewood you wanted — a luxury for the rich in England, commonplace in America.

Nicholas D. Rosen said...

Kaor, Paul!

“Median” means, briefly, that half of a sample are above the median and half below. If the median age of death for adults in New England in 1700 was 71, then as many adults died when older than 71 as died when younger than 71. Please note that the statement was for adults; presumably the median age of death for all New Englanders at the time, including those who died in infancy, and those who died of smallpox, measles, diphtheria, tetanus, and other diseases during childhood, would have been substantial lower.

Best Regards,
Nicholas

paulshackley2017@gmail.com said...

Nicholas,

Thanks. I think I am a bit clearer.

Paul.

Sean M. Brooks said...

Kaor, Mr. Stirling!

And, before Protestantism was forcibly imposed on England, a certain percentage of men and women never married because they became priests, monks, nuns.

I'm reminded of Ireland: before the Potato Blight Famine, many, many of the Irish married very young* and had many children, despite poverty and oppression. One of the consequences of the Famine was the Irish, both in Ireland and in the diaspora, marrying much later.

Ad astra! Sean

*The Church tried to discourage premature marriage, preferring the Irish to wait two or three longer than the minimum set by canon law for a valid marriage (16 for men and 14 for women).