Title. Why do our bodies stop growing at one point and begin to decline in function? If the purpose of life is to live and reproduce, wouldn’t it make more sense to continually evolve and live forever? Also don’t our cells constantly regenerate? So if they do then why do they start to die out?
In: Biology
Without age and death, then parents compete with children for resources, which leads to lower success rate in offspring compared to parents. (imagine trying to compete against parents and grandparents who have experience and skills but no age detriments)
Evolution works on a generational level — meaning that it works over many generations, so the more successful the offspring are to reproduce, the greater the inclination of evolution.
Put these together, and we have “aging correlates to evolution.”
Then, we look at the organisms which don’t age to death, and they tend to be simple and unevolved (eg single-celled organisms, jellyfish, lobster, sea urchin).
The “purpose” of life isn’t a goal exactly, it’s just what happens. If you get something that makes copies of itself, eventually there will be lots of copies of that thing. If all the copies die before they can make more copies, then there are no more copies of that thing.
Once you’ve made some copies of yourself, those copies can make the next round of copies, so you’re technically not needed for that anymore. Also, the fresher copies might be better at making more copies for a variety of reasons, so all you’re doing is taking up food that they could be using to make more copies. So from an evolutionary perspective, it doesn’t really matter if you die after a certain point.
For some things, the best strategy is to put everything you have into making a set of copies, even if it damages you in the process and reduces your chances of survival afterward. As long as there’s a copy running around somewhere, evolution mostly doesn’t care *which* copy it is.
Everything wears out eventually. It starts costing more and more resources to keep an old copy in the same condition as a new copy, if that’s even biologically possible. So nature doesn’t bother with that. It just keeps making the copies that are good at making more copies.
AFAIK it is genetic. It is coded into our cells that they copy a certain way and that way is not 100% efficient and making a copy of a copy of a copy etc eventually wears down and makes mistakes. The reason I say genetic is because cancer cells do not have this flaw. Whatever tweak makes cancer cells be what they are also foxes that part where it makes imperfect copies.
Iirc, there are a lot of reasons. But one od the onez I find interesting are telomeres. This are proteins that are at the end of strands of DNA. As cells divide, the telomeres will start to shorten until the cells are no longer able to divide which causes aging.
Some of this aging will cause organs to stop functioning as efficiently, and adding in minor little mutations that can occur over time such as diseases and cancer, you get death via natural processes.
We don’t know.
Philosophy and science have both tackled this question, and neither have found a good answer so far.
Because entropy is terrible.
There’s only a few ways for things to be put together and work, and many, MANY more ways for things to be put together and *not* work. And the longer something exists, the more and more *slightly* off the way it’s put together will be until it finally reaches one of the infinitely many “doesn’t work anymore” states. Whether it’s external damage building up atom by atom, the cell division process going slightly wrong gene by gene, etc. Anything that can do stuff will cease to be able to do stuff before very long, that’s the nature of everything in this damn universe, *especially* life.
Life has no divined purpose. We have genes which have served us (humans/mammals/lifeforms) well, but it would be a mistake to think these have an overarching purpose or design. The genes have come about through natural selection and have essentially served their purpose after we have procreated. The rest may be “gravy,” although sociologists like to come up with group survival advantages accruing to those with seniors.
To take your question and flip it around, it is indeed possible to have immortal cells – these are cancer cells. The genes for this neoplastic process are inherent to the need for the embryo to invade the wall of the uterus, steal blood and grow. Look at these embryonic cells under a microscope and your will be hard pressed to say they aren’t a doppelganger for a cancer cell.
The reason why mammals die of old age is that the genomes in your cells shortens almost every time it decides. Cells don’t regenerate, they divide.
The majority of a mammalian genomes is made up of junk DNA that exists at the end of the chromosomes that protects the chromosome, called telomeres. When a cell divides, there’s risk of damage to the chromosomes, but most of the damage occurs at the telomeres, leaving the useful part of the chromosomes intact. Over time, the telomeres shortens, so the useful part of the chromosomes starts to get damaged, which leads to abnormal cells and functions.
Life itself is biologically threading on a fine line. Live too long and you now have a very high risk of something screwing up inside you
Just a side note here you don’t “evolve” as you exist. That would have already occurred when you were conceived, based on your parents surviving natural selection.
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