The Mathematics of the Lifespan of Species

skade88 writes "NPR is reporting on a study in which the author claims to have found the formula to predict the average life span of members of a species. It does not apply to specific individuals of that species, only to the average life span of members of the species as a whole. From the article: 'It's hard to believe that creatures as different as jellyfish and cheetahs, daisies and bats, are governed by the same mathematical logic, but size seems to predict lifespan. The formula seems to be nature's way to preserve larger creatures who need time to grow and prosper, and it not only operates in all living things, but even in the cells of living things. It tells animals for example, that there's a universal limit to life, that though they come in different sizes, they have roughly a billion and a half heart beats; elephant hearts beat slowly, hummingbird hearts beat fast, but when your count is up, you are over.'"

"Formula" = Log-Log Regression

[Irate Engineer]

He plots lifetime in days to entity mass in grams on a log-log plot and slaps a line on it. Note that some of the scatter in the vertical axis is up to 3 *orders of magnitude*. Had this been plotted on linear scale it would have looked like Jackson Pollock sneezed on the page. All that can be extracted is that big critters tend to live longer than small critters. So what is new here?

Re:This is not new

[rnturn]

Or correct.

1.5 billion heartbeats for someone who has a constant heart rate of 72bpm would, according to this theory, only have them living for 39.6 years. So color me skeptical.

And frankly, if my heart rate never deviated from 72bpm, I can't say I'd call that living. I'm still going out for a run tomorrow morning.

similar to the argument for creation

[Anonymous Coward]

There must be a creator since it is extremely unlikely we'd exist without hundreds of details being just so (ratio of proton to electron mass, EM vs gravity etc).

The counter is we wouldn't be here to ask the question in all the possible universes where we couldn't exist. Similarly: big animals need lots of resources. Since volume grows with the cube of the size but area with the square getting stuff into a bigger animal takes longer proportionate wise. If big animals didn't live longer they wouldn't exist because they wouldn't be around long enough to get big in the first place (you can't grow an elephant in the lifespan of a fruit fly so the fact that elephants exist implies they must live longer).

Re:That's why I don't exercise

[haruchai]

Funny but I don' t think the math adds up. Let's look at a 50 year period and assume a constant heart rate and skip pesky leap

So for Joe Average, that's 26,280,000 minutes at 70 bpm or 1,839,600,000 beats.

Now in that time Frankie Fitness works out 5 hrs per week for 50 yrs at a heart rate of 150 beats per minute so 780,000 min or 117,000,000 beats during exercise.

Assume that drops his average heart rate to 60 bpm so over 50 years, the number of heartbeats outside when not exercising would be 60 * 25,500,000 = 1,530,000,000.
So Frankie's total heartbeats over 50 years would be 1,647,000,000 so he saves close to 200 million beats over Joe Average.

apropos Redd Foxx quote

[NotQuiteReal]

"Health nuts are going to feel stupid someday, lying in hospitals dying of nothing."

Re:That's why I don't exercise

[PmanAce]

Wrong. By exercising one can lower their heart rate. Around 72 is generally considered the number of beats per minute. From daily exercise I lowered mine to low 50s bpm. What is the difference of the number of beats a year for example between both resting heart rates? Around 11 037 600 beats, looks quite staggering.

Re:This is not new

[u38cg]

So you think you have a power law... [umich.edu]