p.s.Big cats and humans have similar body weights, if not higher.
In: Biology
Larger = longer life is not always true especially in dogs. Most larger dog breeds live 10+ years while smaller breeds can get up to 15.
Because humans now have modern medicine and don’t live in the wild relying on our physical condition allowing us to catch prey.
Captive tigers have an average lifespan of 22 year, almost 50% longer than wild ones.
The larger animal, longer lifespan isn’t a static standard, its just a loose rule that kind of fits a lot of situations. Elephants are massively larger than us but have a similar life span of 70 years (specfically African Savannah elephants).
Larger animals don’t automatically have longer lifespans. The longest-living land animals are tortoises, which can live for 2 or 3 times as long as elephants. Small parrots can also live to be 70-100, far longer than other birds of the same size.
[removed]
Larger doesn’t necessarily mean longer life. For example lobsters aren’t particularly large compared to humans but they technically do not die from old age at all. Lobsters can, in theory, live forever, though there are other limiting factors such as disease and predation.
There’s an interesting theory that heart has only so many beats in it’s life span regardless of which animal it’s in.
There seems to be a correlation between the resting heart rate of animals and their life span. Humans are around 60-100 but athletes can have resting heart rates as low as 40.
Big cats have higher heart rates around 80-150. Dogs and woves are 60-140. Mice are 500-700 and are very short lived.
While elephants despite there size have a resting heart rate of 30 times a minute, and turtles are 25.
The theory postulates that the higher an animals over metabolism, and energy level, the shorter their lives because they burn out their organs more quickly.
While plant eating animals tend to live longer because their metabolisms are slower.
Humans are omnivores, but eating meat is a relatively recent adaption for us in evolution. We are perfectly capable of eating nothing but plants our entire lives. So our metabolisms are a hybrid.
The average human lifespan is upwards of 50-60 years without medical care, but it is often reported as only 30-40 years.
This is because out lifespans are badly skewed because having children for us is very risky. The death rate of children below age of 4 is as high as 20% (without modern medical care). The chances of dying in child birth are also quick high compared to other animals.
Keep in mind also that being a large predator means that you’re constantly hunting large prey animals. So the threat of injury (and infection) is constant.
There’s a lot of things, and still a lot of unknowns.
For one, your assumption that larger = longer isn’t true. So let’s throw size right out the window.
Telomere length and rate of decay varies between species, so that’s likely a factor.
Otherwise, relative lifespan likely has a lot to do with generics. There are lab animals where knocking out a single gene has vastly increased their lifespans.
Genes which contribute to an animals’ death have a lot of ways to spread through a population. A big one is called gene hitchiking. Vastly oversimplifying: let’s say I have a gene where I drop dead at 35; which we’ll call Instant Death. It’s on my chromosome right next to a gene that makes me super fertile compared to the rest of the population from 20 to 30; we’ll call it Ultra Babies.
Any of my offspring carrying Ultra Babies will outreproduce individuals without it, leading to it “going to fixation” within the population (ie becoming a common trait). At the same time, because they’re so close on the same chromosome, Ultra Babies and Instant Death are likely to be inherited together. Instant Death doesn’t kick in until the fertile period is over, too, so it’s not going to decrease the selective power of Ultra Babies; instead, it hitchhikes along to fixation riding on Ultra Babies’ coattails. Give it some time and luck and boom: you have a super fertile species that drops dead at 35.
Humans aren’t a great comparison. Humans are the longest lived warmblooded animal, and that is even considering the effects of medical care.
>We know…
No we don’t. Some birds live to be 100, same with humans, same with blue whales.
Latest Answers