Friday, November 23, 2012

But, Wait...

Human mortality improvement in evolutionary context

Oskar Burger, Annette Baudisch & James Vaupel
Proceedings of the National Academy of Sciences, 30 October 2012, Pages 18210-18214

Abstract:  Life expectancy is increasing in most countries and has exceeded 80 in several, as low-mortality nations continue to make progress in averting deaths. The health and economic implications of mortality reduction have been given substantial attention, but the observed malleability of human mortality has not been placed in a broad evolutionary context. We quantify the rate and amount of mortality reduction by comparing a variety of human populations to the evolved human mortality profile, here estimated as the average mortality pattern for ethnographically observed hunter-gatherers. We show that human mortality has decreased so substantially that the difference between hunter-gatherers and today’s lowest mortality populations is greater than the difference between hunter-gatherers and wild chimpanzees. The bulk of this mortality reduction has occurred since 1900 and has been experienced by only about 4 of the roughly 8,000 human generations that have ever lived. Moreover, mortality improvement in humans is on par with or greater than the reductions in mortality in other species achieved by laboratory selection experiments and endocrine pathway mutations. This observed plasticity in age-specific risk of death is at odds with conventional theories of aging.

I'm trying to think why age at mortality has anything to do with evolution.  Evoluntion involves mutations for variance, and then natural selection to "choose" among variants.  But, wait.... the only variations that matter are those that are relevant for the number, health, and fecundity of offspring.  How old (or how happy) you are when you die doesn't matter much.  And it doesn't matter at all if you if it doesn't increase the number of offspring (do 65 year old men really have children?  I know they could, but...), or the health of your offspring (do 80 year old women take care of great grandchildren?)  (more  after the jump...)

In short, I don't see why having people live for 25 years in a retirement community, and then 10 years in really expensive medical care pavilions, has ANYTHING to do with evolution.  Why would it?

Nod to Kevin Lewis, who was born old.

UPDATE:  Okay, one thing occurs to me.  It could be like sexual selection, if people use the age of the potential mate's grandparents in choosing mates.  I notice that my (potential) spouse's grandparents lived to 100.  So that family has so much extra juice that they live long.  I want my children to live long (for happiness reasons, and because it improves mating prospects, like big antlers for bucks), so I choose mates who have longer-lived ancestors.  Except that there is no way that this is true.  But it's one way it could work...Other suggestions?


gabriel rossman said...

on the update, this must be why porn always starts off with the actors talking about how their grandparents are in their 90s. so sexy.

Anonymous said...

Maybe it has something to do with evolution becuase the selection of other traits that have become attractive in advanced societies correlate with longer mortality, and the selection of those traits has caused an extension in life expectancies.

I am not saying this is the case; I am only speculating that it may be an explanation. I actually do not think that the exension in life expectancy has an evolutionary explanation. We have always have the potential to live this long. We needed mordern societies to be able to achieve this potential.


Tim Worstall said...

The usual story about longer lives is indeed that male fertility lasts a long time.

And access to fertile females depends (largely, as any quarterback will tell you) upon status. Older men do have (largely, perhaps not at age 90 though) greater status and so get access to the fertile females.

Thus the genes for longer lives have come down to us from the male side.

Brandon Berg said...

Maybe that's just how aging works. Damage accumulates over time, eventually leading to decrepitude and death. There wasn't enough evolutionary pressure to result in the development of mechanisms to fully repair that damage, but neither was there any pressure in favor of a self-destruct mechanism that kicks in immediately after the end of fertile lifespan.

sfw said...

In "Time Enough For Love" Robert Heinlein had a short lived millionaire create a foundation that matched people who had all grandparents live to 100+. That was back in the 1950's. Perhaps one of our current crop of uber wealthy could do a similar thing.

J Scheppers said...

I too hope to enjoy a long life but I am not deluded that "25 years in a retirement communinty" may have more burdens to human survival as benefits.