How Long Should We Live? -Part I- Short and to the point


Red Salmon ready to spawn. Photo from


Looking north from the bridge near Chitina.

Looking north from the bridge near Chitina. (Photo credit: Wikipedia)


How long should we take to age and die?

Asked another way, how long does natural selection want us to live? Let’s examine the short life by talking about Pacific Salmon. As an Alaskan, I head to Chitina every summer where I’m allowed to dipnet for thirty Copper River Reds. Dipnetting involves standing on the banks of certain rivers at special times of year and netting salmon as they swim upriver. I always feel a little guilty. Some of them have scars from close calls with sea lions and sharks. They survived the open ocean and then I eat them before they can pass on their genes. If you aren’t familiar with the pacific salmon life cycle, they only get one chance. They grow up in the streams, go to the oceans to fatten up for a few years, return to the stream, where they spawn, and then die.

photo from

photo from

So what causes pacific salmon to die? It doesn’t help that they stop eating once they enter the rivers, and that their bodies, adjusted to seawater, don’t re-adjust to fresh water, but the biggest factor might be buried in their cells. Drastic hormonal changes during spawning shut down many of the fish’s metabolic activities and it’s immune system. It seems that spawning kills them, since castrated salmon live a lot longer. They use all their energy to fight upriver and then they die looking like torn rags thrashing through the water, diseased skin peeling like old wallpaper (lucky for us we eat them long before they get to that state).  Are their deaths programmed into their cells in order to make way for the next generation?

Do hormonal changes after peak reproductive years in humans cause aging for us too? I’ll soon have a post about hormonal theories of aging, but think about the advantages of a death gene that kills the old for the sake of the young. In the case of the salmon, parents die and their carcasses feed the forest which provides cover and shade for the salmon fry growing up in the stream. Their parent’s deaths also mean that in two or three years, when the fry go out to the ocean they won’t be competing with their parents for food.

By Earth'sbuddy

Salmon at the Seattle Aquarium By Earth’sbuddy on wikipedia

Looking forward, if the human lifespan continues to increase, will there be too much competition for resources as more people are born and fewer die?

Or will technology and ingenuity see us through no matter what?

Looking back, has all the time we spent without life-extending technology programmed us to die, to make way for the next generation? Does natural selection want us dead as soon as possible following our peak reproductive years?  I’ll post more about that next Friday, but in the meantime, do you think we should have shorter life expectancies, as a sacrifice for the next generation? Or should we be less like salmon and more like sturgeon, surviving for centuries?

spawned-out salmon. Photo from

spawned-out salmon. Photo from

3 responses to “How Long Should We Live? -Part I- Short and to the point

  1. If salmon die after sex, do humans live longer?

    At least one person thought that being sexually active would extend how long he lived. Mao Zedong in The Private Life of Chairman Mao, by Li Zhisui, Mao’s personal doctor, was convinced that sex was a key to his longevity. (This is an interesting read.) The book describes how Mao selected women at party functions as well as how he liked to receive official visitors when he was naked in his swimming pool. Ironically at least teenager became pregnant when, according to Dr Li, Mao was infertile. He said he never revealed this to Mao.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s