Biology Index
By Richard Bruce BA, MA, and PhC in Economics

The Evolution of Death
The Adaptive Value of Old Age

Why do humans and other animals age? Why doesn't our biology just keep us in our prime so we can have far more children? Wouldn't an animal that did not age be more fit to survive and reproduce?

I was told verbally by a biologist that the death rate from disease, predation, accidents, etc. is so high that there would be little advantage to an animal that did not age. He said that a professor he had worked under had discovered this. The professor did his experiments on fruit flies.

That sounds right for fruit flies. It could even be part of the story for the human race. However, humans and many other animals are relatively immune to predation, at least compared to fruit flies. So for humans, elephants, tigers, and other animals that rarely suffer predation an extremely long reproductive life could increase the number of offspring. So perhaps there is another reason why we have menopause, aging, and death.

Old Age and Death - a Defense against Venereal Diseases

Up until the development of modern medicine venereal diseases were frequently permanent, so they would tend to accumulate over time.

Frequently venereal diseases cause infertility rather than death, for example, gonorrhea and chlamydia. This is probably because the transmission of the disease involves the reproductive organs, so the reproductive organs and therefore the reproductive function tends to suffer from venereal diseases. Of course, this is only a tendency, venereal diseases do spread to and effect other organs of the body.

So before modern medicine the older organisms might frequently be infertile. Therefore they would not produce children, but they would spread the venereal diseases that produced infertility. So the old might be a net drag on the reproduction of the species. What is more, they might reduce the fertility of their own relatives. Genes that caused us to age and die might help us have more descendants, because they might prevent us from contributing to the infertility of our offspring. So animals with the genes for aging might ultimately prove more fit and push the relatively immortal individuals out of the gene pool, into extinction. Perhaps this is one of the reasons we observe aging.

Method, Watching Stupid TV

Scientists frequently describe their method so it can be evaluated, and perhaps replicated. I am describing my method because I hope it will be amusing.

I thought of this as a result of watching a stupid TV show, "The Highlander." Watching stupid TV shows is not generally a very productive way to pursue scientific research, but it does have the advantage that the resource is abundant, because people spend a lot of time watching stupid TV shows.

In "The Highlander" the hero is one of a race of immortals that do not die unless their heads are cut off. The TV episodes revolve around sword fights that end with one immortal lopping off another's head and absorbing his power.

Another major feature is the hero, Duncan MacLeod, jumping in and out of bed with various women. The immortals are infertile or at least do not produce other immortals. It occurred to me that after hundreds of years of bed-hopping the hero must have and be spreading every type of venereal disease. So he was not just infertile, in-spite of being very virile, he must be spreading many venereal diseases and thus making many of his conquests infertile too. Of course the immortals are to some degree magical beings, so the normal laws of biology do not necessarily apply. Nevertheless, this is where I got the idea.

Sex frequently results in reproduction. Sometimes it is the reproduction of us, sometimes it is the reproduction of our venereal diseases, but it frequently results in the reproduction of something, regardless of our objectives. But I digress.

Watching Wildlife Documentaries More Productive

More generally much of my research on biology starts with an aha moment while watching television. Many of the other web pages on biology on this site are based an aha moment while I was watching a television documentary on predators of the African veldt. I saw a spotted hyena running with its weird rocking motion, and thought that is strange. I had come to accept that even though wolves were normally the big pack hunters in most of the world, in Africa lions had seized that niche. But the idea that, spotted hyenas, a giant relative of a mongoose, with a weird rocking run should be second, leaving the smaller relative of the wolf, the Jackel, in third place, was too much. I set up to rework evolution, and the result can be seen in many of these web pages.

A central element of many of my biology web pages, including this one, is a communicable disease. This is a huge factor that biologist simply leave out of much of their reasoning. You can access these on my biology index page.

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