The Naked Scientists

The Naked Scientists Forum

Author Topic: Why are humans so long lived?  (Read 2719 times)

Offline AllenG

  • Hero Member
  • *****
  • Posts: 503
    • View Profile
Why are humans so long lived?
« on: 17/12/2009 13:57:54 »
With the exception of some whales (some of whom have been found with stone harpoons imbedded in their flesh) that may live up to 200 years, I can think of no other mammal that is as long lived as humans, certainly no other terrestrial mammal.

The best theory I can pull off of the top of my head is that being social animals, grandparents must play a significant role in childhood mortality. And I can see how having a set of backup caregivers would be beneficial, more of their descendants  would survive to adulthood hence passing down the traits of longevity to future offspring.  But then would not other social mammals such as the great apes also be as long lived? In captivity, with all the benefits of modern medicine I think a gorilla only lives to be about 45 or so.  So what is special about our physiology that we can pass 100 years--or as in the case of my friend's grandmother, Besse, 113 and counting?

« Last Edit: 17/12/2009 14:01:23 by AllenG »


 

Offline graham.d

  • Neilep Level Member
  • ******
  • Posts: 2208
    • View Profile
Why are humans so long lived?
« Reply #1 on: 17/12/2009 15:28:59 »
It does not always follow that a trait has been selected for by evolution. Often it can be a side effect or even something that has no consequence. I expect there are advantages to children having grandparents though, even as a back-up plan :-) and I would expect that to have evolutionary impact. After childbearing age has been exceeded, it would be an advantage for parents to live long enough to look after their children. This will generally and naturally involve an overlap into grandparenthood. How much this advantage continues after a certain point is difficult to assess. I expect there is a cost to longevity in terms of optimising the age range of a society and a biological one in maintenance of all the body's bits. Each successive generation would be a smaller fraction of a person's genes and there would be more (great)^n grandparents to share the responsibility, so eventually the advantage may be minimal. I expect also that evolutionary changes are slow to take effect. Many of the genes that determine such things will have been selected for thousands or tens of thousands of years ago when societal pressures will have been very different from today. Interesting question.
 

Offline AllenG

  • Hero Member
  • *****
  • Posts: 503
    • View Profile
Why are humans so long lived?
« Reply #2 on: 17/12/2009 20:45:40 »
Chris, I'd love to hear you chime in on a theory.
 

Offline cheryl j

  • Neilep Level Member
  • ******
  • Posts: 1460
  • Thanked: 1 times
    • View Profile
Why are humans so long lived?
« Reply #3 on: 06/12/2011 06:31:33 »
It always seemed strange to me that there is such a difference in the life span of dogs and cats, since they reach maturity at about the same age and are similar in other ways.
 

Offline cheryl j

  • Neilep Level Member
  • ******
  • Posts: 1460
  • Thanked: 1 times
    • View Profile
Why are humans so long lived?
« Reply #4 on: 06/12/2011 06:41:48 »
Maybe the fact that some of us make it to 60 and beyond is just the bonus of nature making sure that the majority of us make it 30, which is the age when our offspring would likely be able to fend for themselves and also reach sexual maturity. If our babies matured at say age 3 or 4, we probably wouldnt live that long.
 

Offline Don_1

  • Neilep Level Member
  • ******
  • Posts: 6890
  • Thanked: 7 times
  • A stupid comment for every occasion.
    • View Profile
    • Knight Light Haulage
Why are humans so long lived?
« Reply #5 on: 06/12/2011 10:17:25 »
Gosh Cheryl, you resurrected an oldie here.

Need I point out that a Koi Carp has been recorded as living just over 220 years, a Parrot about 200 years and (yep, here I go again) many Tortoises have been recorded as living for around 200 years. Timothy (a Testudo Graeca Graeca) was a Royal Navy mascot which lived 175 yrs, then there are Giant Tortoises, noteably Galapagos and Aldabras, Harriet (175yrs),  Tu'i Malila (188yrs) and Adwaita, at 256 yrs the longest lived animal recorded.

Johnathan, of St Helena, has recently been established as the world's oldest living creature at 176 yrs and still going. Tommy, a mere whippersnapper at 112, is thought to be Britain's oldest Tortoise.

Lonesome George, the last of the Galapagos Giant Tortoises of the subspecies Chelonoidis nigra abingdoni, the Pinta Island Tortoise, is estimated to be somewhere around 80 to 100 years old.

There are many tales of Tortoises living well in excess of 100 years, but few stories can be authenticated. Not entirely surprising. If your great great (great?) grandparents bought a pet Tortoise in the mid 19th. century, I doubt they thought they should keep evidence of the fact for us to see 150+ years on.
 

The Naked Scientists Forum

Why are humans so long lived?
« Reply #5 on: 06/12/2011 10:17:25 »

 

SMF 2.0.10 | SMF © 2015, Simple Machines
SMFAds for Free Forums