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Diogenes the Cynic
08-26-2003, 07:57 PM
I was listening to the radio today and they were broadcasting from the Minnesota State Fair. There was a guy on the show who was some kind of alligator expert and he said that alligators can live to be over a hundred years old. I was kind of surprised by that but I already knew that some turtles (or is it tortoises?) can live that long or longer.

It got me thinking about great reptiles (and I know that turtles are amphibians not reptiles) and the dinosaurs in particular. Does anyone know what the average life span was for the big dinosaurs, like a T-Rex or a Brachiosaur? Is it possible that they had really long lives, like maybe in the centuries?

I'm just really curious. Thanks in advance for any answers.

gcarroll
08-26-2003, 08:01 PM
Turtles are reptiles.

Diogenes the Cynic
08-26-2003, 08:03 PM
Originally posted by gcarroll
Turtles are reptiles.
Oh. Thanks.

bup
08-26-2003, 08:03 PM
Back when I researched this in high school, they didn't know. Speculation ranged from ten years to centuries.

That was twenty years ago, though, and only with the materials available to me. A lot of things have happened in Dinosaur knowledge sinc ethen.

Darwin's Finch
08-26-2003, 09:51 PM
I'm feeling rather self-referential today, so see this thread (http://boards.academicpursuits.us/sdmb/showthread.php?s=&threadid=147184), and this one (http://boards.academicpursuits.us/sdmb/showthread.php?s=&threadid=139116).

Polycarp
08-26-2003, 10:05 PM
It's probably worth noting that dinosaurs were archosaurs, the major subdivision of reptiles that included them, pterosaurs (AKA "pterodactyls"), crocodilians, and a couple of loose ends from the Triassic Period of interest only to compleatist vertebrate paleontologies. So their closest living relatives are (1) crocodiles and alligators, and (2) birds.

Both groups are relatively long-lived, especially if you think in terms of the larger birds that get up into small-dinosaur sizes, rather than sparrows and robins.

Finch? There was at one time some speculation that one might be able to determine age-at-death of dinosaurs from something having to do with annual modifications of the bones -- not but equivalent to tree rings. Do you know anything about that -- was the hypothesis tested?

emmaliminal
08-26-2003, 10:24 PM
Originally posted by Darwin's Finch
I'm feeling rather self-referential today, so see this thread (http://boards.academicpursuits.us/sdmb/showthread.php?s=&threadid=147184), and this one (http://boards.academicpursuits.us/sdmb/showthread.php?s=&threadid=139116). Wouldn't it be nifty if people who posted links to other threads included some kind of description of them, so it would be easier for those of us following along to decide whether to risk angering the hamsters for a thread that turns out not to interest us after all? I was just thinking about how nifty that would be.

astro
08-26-2003, 10:34 PM
Originally posted by emilyforce
Wouldn't it be nifty if people who posted links to other threads included some kind of description of them, so it would be easier for those of us following along to decide whether to risk angering the hamsters for a thread that turns out not to interest us after all? I was just thinking about how nifty that would be.

When Darwin's Finch posts a link you can usually assume it's on point.

Diogenes the Cynic
08-26-2003, 10:55 PM
Thanks for the links, Finch[/c]. I should have searched before posting a new thread. I was arrogant enough to think that I had come up with an original question.

So it sounds like we just don't really know, huh? Could be ten-twenty years, could be three hundred. I like to think that they lived for centuries, it just seems aesthetically satisfying to me.

As to [b]Poly's question about bone development, I wondered that myself. The "tree ring" analogy even wandered through my head, though knew it was silly.

Evil Captor
08-26-2003, 11:14 PM
If they lived for centuries, it might explain all the arthritis, and also bring new light on the theory that they died of constipation.

emmaliminal
08-26-2003, 11:18 PM
Originally posted by astro
When Darwin's Finch posts a link you can usually assume it's on point. Noted, and thanks. But... it might not be on point for me, if you see what I mean. I'm not the OPer, and I look at a lot of threads for reasons other than getting the answer to the original question. I think that's pretty normal.

And while from now on I'll probably remember that Darwin's Finch is a to-the-point poster, y'all don't keep a scorecard handy, right? There's a lot of Dopers to keep track of!

[/hijack]

Darwin's Finch
08-26-2003, 11:23 PM
Originally posted pby Polycarp
Finch? There was at one time some speculation that one might be able to determine age-at-death of dinosaurs from something having to do with annual modifications of the bones -- not but equivalent to tree rings. Do you know anything about that -- was the hypothesis tested?

The annular-rings thing didn't go anywhere, as near as I can tell. The rings, which seemed indicative of ectothermy, were only seen in some specimens, while others possessed Haversian canals - a sign of endothermy, and others show signs of neither. This site (http://isgs.uiuc.edu/dinos/de_4/5c51dbb.htm) has some info about bone histology of dinosaurs, and how it compares to other vertebrates; it seems that the bone formation of dinosaurs is all over the place as a group, so it's difficult to make any general conclusions about age based on them. Add to this the observation by authors such as Gregory S. Paul that records of juvenile bone formation can be lost in an adult, and the whole thing starts to look like a lost cause.

Originally posted by emily force
Wouldn't it be nifty if people who posted links to other threads included some kind of description of them, so it would be easier for those of us following along to decide whether to risk angering the hamsters for a thread that turns out not to interest us after all? I was just thinking about how nifty that would be.

My apologies. But, in this case, if those threads did not interest you, this one shouldn't have, either, since they're all on the same topic.

Beryl_Mooncalf
08-27-2003, 12:37 AM
Here is some info on the bone growth ring theory.
dino lag (http://enchantedlearning.com/subjects/dinosaurs/anatomy/Age.shtml)

I think I remember reading that reptiles continue to grow for most, if not all, of their lives? Maybe that explains the growth rings.

They estimate the life span to be about 100 years for a large one here, less for smaller dinosaurs.

j.c.
08-27-2003, 02:13 AM
When Darwin's Finch posts a link you can usually assume it's on point. Great! Like emilyforce I'm happy to keep track of everyone and urge friends to read the SDMB. Why should a first-time reader worry about what's at the other end of a link.

Seriously, I mean. Come on.

Colibri
08-27-2003, 12:42 PM
Among vertebrates, life span tends to be correlated with body size. A mouse may live a year or two, a cat 15, a horse 30, an elephant 70+.

Based on this correlation, one might expect the largest dinosaurs to have a life span of several centuries. But there is no real way to know if this was true based on present evidence. In any case, the correlation doesn't hold in all cases. Blue whales are thought to have an average life span of only about 40 years, while humans have a much longer life span than might be expected from our body size.

casdave
08-27-2003, 12:56 PM
Yes but the human lifespan is somwhat influenced by medicine, readily available supplies of food and clean water.

If you wish to include humans in your comparisons then surely one must use something like African bushmen, or Amazonian tribespeoples whose lives are far shorter on average.

Gong back only a couple of centuries would show humans having much shorter lifespans, in fact look around the lifespan in some third world countries where infant mortality is very high.

Put humans into this frame of referance and perhaps we would then fit in to the bodysize/lifespan ratio better, or maybe we would not.

Colibri
08-27-2003, 01:32 PM
Originally posted by casdave
Yes but the human lifespan is somwhat influenced by medicine, readily available supplies of food and clean water.

If you wish to include humans in your comparisons then surely one must use something like African bushmen, or Amazonian tribespeoples whose lives are far shorter on average.

Gong back only a couple of centuries would show humans having much shorter lifespans, in fact look around the lifespan in some third world countries where infant mortality is very high.

Put humans into this frame of referance and perhaps we would then fit in to the bodysize/lifespan ratio better, or maybe we would not.

Actually, I should have been clearer. Humans have a disproportiately long life span, both average life span - which as you say has been greatly lengthened by medical advances in the past few centuries - and maximum life span - which as yet has not been extended all that much.

A dog, no matter how well cared for, has never lived more than 30 years. The oldest horse on record was 56 years. In contrast, the oldest human confirmed by the Guinness Book of World records reached more than 120 years. This is perhaps three or four times the maximum age reached by any mammal of equivalent body size, and far in excess of anything that can be accounted for simply by medical advances. (Mind also, even in ancient times the occasional human lived for more than a century.)

Years ago I read an essay by Isaac Asimov discussing the problem. He calculated that almost all mammals, from mouse to elephant, have roughly the same number of heart beats in the course their maximum life spans (mice having a much faster heart rate than elephants.) Humans, however, were way off the curve.

Personally, I suspect the reason has something to do with the fact that humans are neotenic compared with our closest relatives, the great apes. We as adults are more similar to juvenile apes than we are to adults, due partly to the fact that our growth and maturation is significantly slower. This retardation in developmental rates, and maturation in a "juvenilized" form, may somehow result in slower aging in general. But this is just speculation.

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