Why do some species live so much longer than others?

Factual Questions
1

Do you have any opinions as to what are the factors that determine the average life span of different species?

If you accept the basic principles of Darwin’s Natural Selection Theory (which tends to make sense to me), why is it the expected max lifespan of Amazon parrots is about 104 years while the expected max lifespan of African Grey parrots is only about 73 years and the expected max lifespan of canaries is only 24 years? The following link shows a chart of the Expected Maximum Life Span of Various Animals:

http://sonic.net/~petdoc/lifespan.htm

The real question I’d like to ask is why is it that this Giant Seychelles Tortise has lived for 183 years? What could the factors possibly be that enable Giant Tortises to live so long? The following link is a story about the oldest living animal on earth. It’s a Giant Seychelles Tortise that is 183 years old.

I would think that if there is a “Creator”, They would have some reasons why certain animals are designed to live longer than others and maybe we can learn some lessons from the lifestyles of these animals to enable us to live longer?

2

Many large birds have few or no natural predators, so they can invest in longevity. If you are a small creature like a wren or a mouse there is no point in body maintenance since you’re going to be eaten soon by a predator. The ones who simply breed as fast as possible have the most chance of having at least a few offspring survive until they can pass along the genes.

Tortoises and elephants have no predators except humans.

3

Also, the article in the link points to other lifestyle factors such as “healthy eating”. However, I figure that many species have to invest most of their energy into finding any kind of food - healthy or not. They even likely have to take chances trading off their safety for food. If they come out of a safe place to try and find food, it would raise the probability they could get eaten.

So, that ties in with your point about predators and I thank you for that info.

4

The answer to most questions like this is niches. Animals are not designed to live long. They are not designed to do or be anything. Instead they evolve particulars to fill the empty niche in which they wind up fitting.

Large numbers of trade-offs are involved. Does a species have many offspring that leave early or fewer that stay and are cared for? Do they breed often or rarely? Do they live fast lives with much movement or slow lives that conserve energy? Do they have a wide range of foods or a narrow one? And on and on, for hundreds of similar issues (which are continuums not dichotomies).

No species can simply choose to adopt certain winning techniques of another species. They are wired together to make a unique bundle. That’s the bundle that wins in their particular niche. If the niche changes, then species either die off completely or die off partially until many generations later some descendants outcompete other species for survival.

And of course there is no Creator, of any definition, behind any of this.

5

He made the tortoises, elephants and whales last a long time to give Him plenty of free time to work on new beetles - of which He is inordinately fond.

6

I liked this post - even though I had to look up the word “niche”. Here is what I found, by the way:

Niche - “a place or position suitable or appropriate for a person or thing: to find one’s niche in the business world”

I’m not sure whether I agree with you about a Creator. But I don’t think that is very important since people are certainly entitled to their individual opinions about that.

I’m guessing that animals that live fast lives with much movement would tend to have a shorter lifespan than those that live slow lives that conserve energy. But how do you reconcile that with the idea that excercise is important for a long life. Would you agree that a sedentary lifestyle tends to reduce lifespan?

7

Here’s a more specific look at the term in this context.

Not in GQ, they aren’t.

You mean, like the Giant Seychelles Tortoise?

What’s an effective strategy for one species is not necessarily so for others. It may not be effective even for different individuals within a species.

8

[QUOTE=Exapno Mapcase]
And of course there is no Creator, of any definition, behind any of this.
[/QUOTE]

Moderating

GQ isn’t the place to discuss religious opinions. Let’s keep this discussion to scientific explanations.

Colibri
General Questions Moderator

9

Well some tortoises live so long cause they have an extremely slow metabolism right? A lot less oxidative stress and cellular damage. I recall reading early explorers of the Galápagos Islands would take the tortoises on the ships for food because they can go a year without eating or even drinking. Some studies suggest caloric restriction extends human lifespan as well.

10

Ha Ha! Nicely done. I got a good laugh from that. Good for you.

:slight_smile:

11

Mice, not humans. We don’t have the data on humans quite yet.

But be careful about drawing inferences about mammals (endothermic) from facts about reptiles (exothermic).

12

Also, just plain tasty!

13

I’m a bit surprised. If you look at life span vs size, with a couple of exceptions, there is a strong trend that larger is related to longer lived. Most vertebrates get about 2 billion heartbeats. Elephants and tortises have slow pulse rates, and live a looong time. Mice and small birds have frantically beating hearts and seldom see a second year. We don’t know why some of the parrot family go so long, but they almost certainly don’t last that long in the wild.

The other interesting exception is dogs, the smaller ones tending to outlast the bigger ones. Sadly, the most annoying dogs outlive the mellow companions.

And, of course, us. My second billionth heartbeat was about 20 years ago, and I could easily have another billion to go.

14

Don’t forget the longest-lived animal ever recorded: a clam named Ming. It lived 507 years, and probably would have gone on longer if it hadn’t been accidentally killed by the researchers who opened its shell to find out how old it was. :smack:

15

To expand a little on what MLS said, one of the leading theories for why we age, and why we have such different lifespans is like this:

Imagine you start with a species that doesn’t age.
Now this of course doesn’t mean it’s immortal; it can still be eaten by predators, can still starve, freeze to death etc.

Let’s say this species has so many environmental hazards that the average individual has a 50% chance of dying every year.

Now say a mutation occurs that will negatively affect an individual after about 15 years old, but have no effect before that. Well, few individuals are going to live to be that old, so there is little selective pressure to remove that mutation, and such mutations will spread through the population just through genetic drift.

Now, say we have a mutation that has positive effects in early life, then negative effects later. For example, a gene that will aid calcium absorption, so that an individual’s bones will harden faster but later will have the side effect of hardening arteries. Well, as long as “later” is beyond say 8 years for our hypothetical species, such a mutation will be aggressively selected for. Because again, few individuals are living long enough to experience the side effect, most individuals will just see the benefit.

So over time our “non-ageing” species will accumulate such mutations, and a typical 7-year old individual will look like crap and have impaired function in just about every organ.

Going back to the OP then, one of the key factors is simply what your life expectancy if you didn’t age would be. So bats live much longer than mice, despite being approximately the same size because of bats’ relatively safer living conditions.
And despite the terrible living conditions of humans before the modern age, we nevertheless became pretty good at surviving and live accordingly longer.

Anyway, that’s the theory.

16

The suckiest thing is that dogs only get 10-20 years, while their human companions have to soldier on when they go. That ain’t right.

17

This is true. However, although it may apply to indidual species, it doesn’t seem to apply to individuals within the same species.

It’s like Exapno Mapcase said above. “What’s an effective strategy for one species is not necessarily so for others. It may not be effective even for different individuals within a species.”

When it comes to humans, the oldest individuals usually tend to me small thin people. Large, heavy set people tend to die off much younger.

I know this isn’t exactly on point, but one man who lives near to me kept getting heavier and heavier. He must have weighed around 400 pounds and he was only 35. He died. The doctors said his body was too heavy for him to breathe and he died for a lack of oxygen. Very strange.

I talked with him a few times and he told me that he wanted to lose weight but he couldn’t because he just had “a big appetite” and there was nothing he could do to change that. I felt sorry for him. But I thought his comment about having a big appetite just didn’t ring true. I used to be obese and the reason I ate was emotional. I felt something was lacking from my life and I was unhappy about that. This man essentially ate himself to death. I know it’s not directly on point as far as this thread goes. But I think about him sometimes when I have a craving for that extra piece of pie.

18

There are various factors that impact lifespan between species, several already mentioned.

  1. As mentioned, the impact of predation and other environmental impacts like pathogens. If under higher predation/pathogen pressure then hitting reproductive maturity quickly is selected for, with no regard to how it impacts longer lifespan negatively as few make it long enough for that to matter.

  2. Given relatively little predation pressure, does an individual add to the the odds of genes being passed on multiple generations hence by sticking around longer, after reproduction days are over? IOW is there a selection pressure for longevity? Given an animal with limited period of reproductive capacity that can only occur in animals that live in social groups in which elders can contribute to kin survival to a greater degree than feeding them costs.

  3. Yes in general the lower the heart rate the longer the lifespan. True within humans as well. Think of it as a marker of how fast the metabolic clock is running if nothing else.

  4. Within humans shorter generally correlates with slightly greater lifespan as well. Growth hormone signaling pathways and its relation to the mTOR pathways are speculated to be key. Yes, same is true within other species as well. And in dogs it also seems to be related to part of that growth hormone pathway, in particular to IGF-1.

  5. Elephants are a particularly interesting case study, especially in relation to their very low rate of cancers.

  6. And pygmies are a very notable exception to the correlation of human short stature with longer lifespan. They sexually mature early and life expectancy is about 18. Speculations abound. Maybe the short life expectancy (due to a variety of factors) came first. In this thinking “their early deaths are the driving force behind both their small size and their shorter growth spurts. It pays pygmies to divert resources away from growth and towards having children as early as possible, to compensate for their limited years.” Alternatively the genes that help them resist the pathogens in their environment may just have short stature and early maturity as a secondary impact.

  7. Thoughts on long lived turtles. Relatively protected from predation, long reproductive period but infrequent opportunities, low metabolic rate (Galapagos Tortoise heart rate 6 beats per minute)

19

Another point is that very few animals live much past reproductive age. If you live to be a thousand, but finish all your reproducing by age 20, then evolutionarily speaking, those last 980 years are completely irrelevant. The only exceptions are those rare few species (us among them) who, even after we’ve finished reproducing, can still influence the success of our descendants. My grandfather didn’t reproduce at all in my lifetime, but I still learned a lot of useful and valuable lessons from him.

20

Oh. No idea what evolutionary pressure has made the hydra (a tiny freshwater polyp) virtually immortal. But genetically it seems to do with the FoxO gene. And that is of possible impact on human aging as well.