The science community's past and present views on most animals having the same number of heartbeats

I’m curious about the theory that most animals, as a general rule, have the same number of heartbeats. In the 1970s, did the scientific community generally accept this theory, or did it generally reject the theory? And today, does the scientific community generally accept this theory, or does it generally reject it?

That’s not a* theory * because there’s no why or how in it. A theory would be something like “Most animals have the same number of heartbeats over a lifetime because…[insert why or how here].” What you have, if it is actually true, is what’s called an observation, or sometimes a natural law, if it is nearly universally true. The scientific community neither accepts nor rejects these. They simply are.

Of course, it’s possible for someone to make measurements on, say, five species of animals, discover they have the same number of heartbeats over a lifetime, plus or minus 20%, and then leap to the conclusion that all animals have the same number of heartbeats over a lifetime. Most scientists would laugh at this. Not at the proposition per se, but at the folly and cluelessness of leaping to such a broad conclusion from such meager data.

It’s also worth noting that the “scientific community” doesn’t actually do any accepting or rejecting of theories. It lacks (say) a Science Legislature that would pass the requisite resolutions. What happens, instead, is that individual scientists accept or reject theories as their own individual judgment and experience suggests. Indeed, to be a scientist at all, you have to trust your own judgment and experience much more than the opinion of others. If you are the kind of person who can be convinced that something is true merely because lots of other people – even *everybody * else on the planet – say its true, then you are not a scientist. A scientist trusts only his own senses, and what is consistent with that experience.

Whoops! Hehe! Sorry! I didn’t know the difference between a theory and an observation until you told me! I’m definitely not a scientist. But all I was wondering was whether the observation about most animals supposedly having the same number of heartbeats (1,000,000,000) has been generally accepted as true or as false.

Do_we_have_a_finite_number_of_heart_beats ?
I agree with the idea that the graphs only just happen to show a misleading correlation

The heart would have lived longer ,the animal dies at that age due to all sorts of other reasons not related to having consumed all their heart beats.

But is it popular to predict lifespan of animals other than humans, based on what age a certain animal reaches about 1 billion heartbeats?

In other words, is the notion that animals typically live for 1 billion heartbeats largely accepted by most biologists and cardiologists, or is it largely rejected by most biologists and cardiologists?

There are two real correlations: First, smaller animals (well, all the examples given are mammals) tend to have faster heart beats. Second, larger animals tend to live longer. These two things just happen to combine to mean that, vaguely, animals tend to live about the same number of heart beats (about 100,000,000 to 10,000,000,000). Read Isilder’s link. There’s no reason to think that the number of heart beats is actually any limit on lifespans.

Rejected. - But to say it that way is a bit misleading because it suggests that the idea was, once, at least seriously entertained by at least a few biologists or cardiologists, and I am pretty sure it wasn’t.

It was a rule of thumb. And the whole point of a rule of thumb is that it’s not to be taken literally, but rather as a general guide.

I don’t think it was ever supposed to be interpreted as directly causative, that animals die when they run out of heartbeats. Rather, heart rate was used as a convenient proxy for overall metabolic rate. Creatures whose heart beat faster also breathe faster, digest their food faster, and so on.

There is an overall negative correlation between lifespan and metabolic rate, but there’s a whole lot of spread around the correlation. It’s not a natural law or anything.

Mammals, not “animals”. Many animals don’t even have hearts. :wink:

pulse rate of 60bpm
x 60 minutes = 3600
x24 hours = 86,400
x365 days per year = 31,536,000 beats per year
1,000,000,000/31,536,000 = 31.71 years

Humans don’t seem to fit this rule very well.

That was the point of the original story (every time I heard this, anyway) – that humans live much longer, in terms of heartbeats, than other mammals.

Might I ask where you got this notion in the first place?

I’ve seen this “fact” presented off hand in an evolution class, as a prelude to more in-depth discussion of the evolution of life span. At least I definitely remember seeing the body size vs life span graph, perhaps not the heart rate vs life span graph.

There’s two interesting correlations at work her. One, as mentioned above, is that higher metabolic rate correlates with lower life span. This mechanism here is easy to understand, since respiration produces damaging reactive oxygen species as a side effect.

The second correlation is between size and heart rate. A smaller heart will have to beat faster to effectively pump blood, and a larger heart has more mass and cannot beat as fast. Similarly, a larger circulatory system has more capacity to even out pulses of blood pressure, so there can be more time between heartbeats.

This site discusses it in more detail, tying it to the “Kleiber Ratio”:

More on Kleiber’s Law here.

Actually, I believe the average heart rate of humans is 72bpm, not 60bpm. A google web and book search give 72bpm as the average human heart rate. So:
heart rate of 72bpm
x60 minutes = 4320
x24 hours = 103,680
x365 days a year = 37,843,200
1,000,000,000/37,536,000 = 26.42 years.

Eh, Mr. Bill’s figures were fine for a rough estimate, which is really all that’s called for here.

Largely because they have medical intervention to expand their lifespans. Longevity beyond the 30s might be rare among humans living in the wild, without access to medical care, and other factors like technologies that minimize starvation, exposure, accidents and predators. Domesticated animals, provided with similar human care, probably live somewhat longer than their wild ancestors did.