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I was curious, why is it that dogs will live somewhere in the 10-20 year range, but humans make it to 80, and animals vary so much?
Woopydalan said:It seems larger animals live longer than smaller ones generally (whale vs. house fly).
Given an average human heartbeat of 60bpm that means a human life expectancy would be 3 weeks. This doesn't make any sense regardless of how many beats one proposes.spacester said:I remember hearing once that if you measure lifespan in heartbeats instead of years, most animals (or was it just mammals?) come in at about the same number, about 2*10^6 or something.
The simple, but admittedly not very helpful, answer is evolution. Dogs who live to be 80 don't leave any more descendants than those who live to be 20.Woopydalan said:I was curious, why is it that dogs will live somewhere in the 10-20 year range, but humans make it to 80, and animals vary so much?
Heart beats represent energy expenditure. Life span is not determined by the number of heart beats, but the number of heart beats represents the amount of energy expended by mammals; it is a marker of our energy expenditure of cells, which still makes it useful.
It has a table, but I would not trust the graphs or mathematics there. It looks like a homework project with the target "we have to find some relations to get a good grade".Evo said:This has come up before. And as someone mentioned, there seems to be a correlation with heart rate and life span. I can't find the refernce i used last time, but this has a table. Scroll down to Lifetime Heartbeats and Animal Size.
http://www.sjsu.edu/faculty/watkins/longevity.htm
Yeah, it's not the study I originally found a few years back. The second goes into more detail.mfb said:It has a table, but I would not trust the graphs or mathematics there. It looks like a homework project with the target "we have to find some relations to get a good grade".
The life expectancy of humans is a bit special anyway.
Abstract
Among mammals, there is an inverse semilogarithmic relation between heart rate and life expectancy. The product of these variables, namely, the number of heart beats/lifetime, should provide a mathematical expression that defines for each species a predetermined number of heart beats in a lifetime. Plots of the calculated number of heart beats/lifetime among mammals against life expectancy and body weight (allometric scale of 0.5 x 10(6)) are, within an order of magnitude, remarkably constant and average 7.3 +/- 5.6 x 10(8) heart beats/lifetime. A study of universal biologic scaling and mortality suggests that the basal energy consumption/body atom per heart beat is the same in all animals (approximately 10(-8) O2 molecules/heart beat). These data yield a mean value of 10 x 10(8) heart beats/lifetime and suggest that life span is predetermined by basic energetics of living cells and that the apparent inverse relation between life span and heart rate reflects an epiphenomenon in which heart rate is a marker of metabolic rate. Thus, the question of whether human life can be extended by cardiac slowing remains moot and most likely will only be resolved by retrospective analyses of large populations, future animal studies and clinical trials using bradycardic therapy.
The transgenic manipulation studies are confounded by the problem that transgenic manipulations often also affect body size. This raises issues about how metabolic rate should be normalised (see discussions in Ramsey et al., 2000; Speakman et al., 2002) that are not yet resolved. How this normalisation is performed dramatically alters the conclusions that are drawn about the effects of metabolism. Some researchers therefore claim that the transgenic effects act via metabolism; others suggest there is an independence of the effects from metabolism. In other species, particularly mice, the measurements have simply not yet been made to indicate what is going on. This problem of normalising for effects of body size also besets the whole area of whether caloric restriction acts via a decrease in metabolism or not (reviewed in Ramsey, 2000). Comparisons across different strains of dogs and mice are much clearer in suggesting a positive association of metabolism and longevity, and this effect was also found in the single comparison made to date of individual variability within a strain of mice
There are many factors that contribute to the variation in life span among animals. Some of the main factors include genetics, environmental conditions, and evolutionary adaptations. Some animals may have inherited genes that allow them to live longer, while others may be better adapted to their environment and able to survive for longer periods of time.
Animals with shorter life spans have evolved different strategies to ensure their survival and reproduction. Some species, such as insects, have a shorter life span but are able to produce large numbers of offspring in a short amount of time. Others, like birds and mammals, have longer life spans but invest more time and energy into caring for their young.
Larger animals tend to have longer life spans because they have slower metabolic rates and are less susceptible to predation. This means that they are able to conserve energy and avoid being hunted, allowing them to live longer. Additionally, larger animals have more cells and tissues, which can help them repair any damage or injuries that may occur over time.
Yes, environmental factors can have a significant impact on an animal's life span. For example, animals living in areas with abundant food and resources tend to have longer life spans compared to those in harsher environments. In addition, exposure to toxins, pollution, and other environmental stressors can shorten an animal's life span.
While there have been some cases where human intervention has extended an animal's life span, it is not a common occurrence. In some cases, animals may live longer in captivity due to access to medical care and protection from predators. However, it is important to consider the ethical implications of artificially extending an animal's life span and whether it is in their best interest.