| DeathDeath. Why it happens? Why do we die? Why | | | | selected during the evolution. Any new animal, be it a |
| do animals die? Why do plants die? What is the need | | | | mouse or a human, starts life as a single cell. That cell |
| of this? In my opinion mechanism of death was | | | | differentiates and develops into the complete animal. |
| selected during Evolution.From the position of | | | | It assures that a rare advantageous variant sequence |
| Darwin's theory of Natural Selection everything, that | | | | of DNA will be rapidly propagated by natural selection. |
| benefits survival of species and gives advantage in | | | | It is much easier to reproduce and maybe get some |
| Natural Selection, is preserved in following | | | | new genes or favourable mutations starting from a |
| generations.Improvements were often left | | | | single cell than starting from a whole multicellular |
| unchanged from the moment of life appearance. | | | | organism. Functions of most genes will have been |
| Though there could be other ways, certain | | | | optimized by random point mutation and selection in |
| mechanisms were accidentally selected. These | | | | any given species. Signalling between cells during the |
| improvements are reproduced in the genome of | | | | development process ensure that everything ends up |
| more complex species. Billions of years ago, according | | | | in the right place. Tiny changes in these Signalling |
| to the theory of evolution, chemicals randomly | | | | processes can have very large effects on the |
| organized themselves into a self-replicating | | | | resulting animal. Genome, with at most forty-sixty |
| molecule.Lightings and UV-radiation helped to create | | | | thousands genes, is able to specify the creation of a |
| first organic molecules. This phenomenon is | | | | human body containing trillions of cells, billions of |
| reproducible in a lab. The experiments were described | | | | carefully wired neurons and hundreds of different cell |
| in 1950-60.First self-replicating molecules were | | | | types all amazingly sculpted into organs as diverse as |
| probably RNA. First enzymes were probably RNA - | | | | the liver and the brain. This is why mechanism of |
| enzymes. Then proteins, DNA and more complex lipid | | | | proliferation of fertilized oocytes was selected.Hence, |
| molecules and polysaccharide came to the | | | | having younger (smaller) and older (bigger) animals |
| scene.Death as it is did not exist at the stage of | | | | make sense.But there is the problem: adult animals (or |
| Primeval Soup . Sure some organic molecules were | | | | plants) consume all the nutrition around and there is |
| destroyed , some new created. But in general it was | | | | not much left for next generation.Then it is why |
| still that swirling and bubbling primary broth - quasi | | | | mechanism of Death was selected as a mean for |
| alive in our understanding as a mixture of biochemical | | | | next generation to establish.Imagine the |
| reactions.Everything in the evolution was build from | | | | following:First, mechanism of proliferation was |
| the previous blocks selected sometime by | | | | selected . If mono-cellular organism does not have |
| accident.Appearance of lipid membranes allows to | | | | mechanism of reproduction it does not produce |
| compartmentalize the primary broth and create first | | | | offspring with possible favourable mutations. Let say |
| cells.At the cellular stage we could already talk about | | | | there are primitive bacteria spontaneously created in |
| the Death. Cell is destroyed, membrane is broken, | | | | primeval soup. Just few of them. They consume |
| everything leaked out. This is the Death.Content of | | | | nutrition, they live happily, practically immortal but |
| cell inside lipid membrane is irradiated. Process of | | | | they do not divide. Then set of enzymes appeared |
| crazy molecular swirling is messed up by free radicals | | | | during mutations. The set allows bacteria to split. |
| irreversibly. This is also signs of Death.Yet at the | | | | Synthesis of the new set is disadvantageous. It |
| cellular stage we cannot talk about Aging. Death at | | | | requires additional energy and nutrition. But advantage |
| this stage is accidental, not programed.Organic | | | | of splitting allows new mutants immediately overgrow |
| molecules may age (oxidation, conjugation, etc.) and | | | | non-proliferating cells. Selection is really |
| cell would die. But damaged molecule are repaired or | | | | cutthroat.Bacteria growing in a tube represent mini |
| synthesized fresh usually. Hence, no good reason for | | | | evolution. Any bacteria that fit for the environment |
| a single cell organism to age. Irreparable damage from | | | | are also selected on the ground of simplicity. In a |
| external cause leads to Death, not Aging. This is | | | | toxic environment (antibiotics) mutant bacteria having |
| accidental death. For multicellular organisms, there is a | | | | a new mechanism of neutralisation would survive. But |
| parental organism that ages and eventually dies after | | | | the more simple bacteria will eventually overgrow |
| next generation is born. For mono-cellular organism, | | | | complicated ones. Unless complication gives big |
| there is parental organism that divides and becomes | | | | advantage that outweigh the benefits of simplicity. |
| the next generation. There is no Aging leading to | | | | Another example: HIV virus is very complex compare |
| death of parental organism.Mono-cellular organisms | | | | to some other viruses. But because of the |
| are practically immortal in a right | | | | complexity it evades immune response. This is why it |
| environment.Mechanism of division was selected | | | | is so successful. For humans there was some |
| during evolution. Cell has volume (3-D). Surface | | | | discussion that hernias are direct problem of erect |
| membrane is measured in square units (2-D). Growing | | | | posture. So erect posture leads to disadvantage. |
| beyond limits cause inadequate supply of nutrition | | | | From the other hand erect posture frees the hand, |
| from environment. Division solves the | | | | that allows to produce the tools and this gives huge |
| problem.Microbes, bacteria are immortal. Some divide | | | | advantage in the survival in natural world by creating |
| every 20 minutes. In a an hour they multiply 8 | | | | possibility to adapt to virtually any condition.All high |
| times.Tumour cells divide slower. They are eukaryote. | | | | animals have just 4 extremities. Obviously it is enough |
| Most aggressive divide once a day. There is no need | | | | in cutthroat environment. Growing additional couple of |
| for Aging.They would die if you do not feed them. | | | | extremities will consume much more resources and |
| They die when you kill them with undiluted bleach in a | | | | take much more time, not giving big advantage in |
| flask. Otherwise they grow unstoppable. No | | | | speed or protection of an animal. Thus, danger of |
| aging.Multicellular organism supposedly has several | | | | losing one of the limb is not so big as the danger to |
| control mechanisms to prevent excessive growth | | | | not proliferate fast enough.Bilateral design of majority |
| and division, to kill an extra cell. Apoptosis, | | | | of animals was chosen at the level of primitive |
| programmed death, is used.Cancer cells often loose | | | | species. Though lower multicellular organisms may |
| the control mechanisms.A scientist from Yale once | | | | have 3-side symmetry or 5-side symmetry like sea |
| pointed out to me that we can not say these cells | | | | stars. Often something chosen in the selection |
| are immortal. Maybe they divide and parental cell dies. | | | | becomes building blocks for higher species. Maybe |
| Indeed. We do not follow the fate of every individual | | | | 5-side symmetrical tiger would be possible but it |
| cell during experiments. They should give more | | | | requires intermediate chain.The same is true for the |
| children cells than parental cells die. Otherwise there | | | | mechanism of Death. Once chosen, it is replicated in |
| would not be the multiplication. It is a possible | | | | all higher organisms. It should give an advantage in |
| scenario. We do not follow the fate of individual | | | | ultimate species survival. Otherwise it loses sense and |
| bacteria as well. Maybe they actually undergo | | | | species would be wiped out.So, what is advantage |
| aging.From the other hand some experiments | | | | for Death?Immortal and childless animals are growing |
| suggest that new cells contain roughly half of the | | | | and growing. Mutations lead to species producing |
| parent cell after division. So it is not Death or Aging. | | | | offsprings. They have disadvantage of been more |
| Next generations contain 1/4, 1/8, 1/16 and so on of | | | | complex. But advantage of proliferating animals is |
| the parent cell. Any mechanism that is more complex | | | | occupation of vaster areas. They displace immortal |
| than simple division would cause disadvantage in | | | | and childless species. Now, if proliferating animals are |
| evolution and would be quickly eliminated. On the level | | | | immortal they do not give offsprings enough space |
| of mono-cellular organism neither Aging nor Apoptosis | | | | or food. Next steps of mutation brought mechanism |
| make a lot of sense. Though Nature often have | | | | of programmed death at certain age.Let consider |
| hidden reasons.Flick's phenomenon and telomeres | | | | situation when out of two species one is immortal |
| shortening make sense for a multicellular organism. | | | | and producing offsprings, other is mortal with |
| Cells of multicellular organism do age. They stop | | | | offspring production as well. Mortality looks like an |
| dividing after 70 divisions or so.A multi-cell organism | | | | obvious disadvantage in stable environment. Adult |
| has clear cut advantage over a mono-cell.Why would | | | | organism are more powerful and more protected |
| mechanism of Death selected for multicellular | | | | compare to juvenile.However, next catastrophe will |
| organisms? Scenario could be the following.Big | | | | wipe out all the species altogether. Only some |
| organism have more advantages compare to smaller | | | | mutants can adopt to new environment. But |
| one - stability, protection, etc. There are not so | | | | "mutant" for a multicellular organism imply that the |
| many natural enemies for whale or elephant because | | | | mutation happened when the organism had only one |
| of their size. Large animals could be brought down by | | | | cell (the stage of fertilized oocyte for example). |
| bacteria, viruses, small parasites, and lack of available | | | | Otherwise it needs precisely the same mutations on |
| food. Rare predator attack whale or elephant.No | | | | the level of several cells - infinitely impossible |
| wonder that evolution was going into the direction of | | | | event.Thus, any species that had the mechanism to |
| bigger animals - just look at giant bones of dinosaurs | | | | allow next generation to flourish (mechanism of |
| and you will feel some appreciation.Millions years ago | | | | programmed Death) will have advantage. They |
| not only Dinosaurs but also insects or crustacean | | | | produce more offspring than immortal species. Death |
| were enormous. Cockroaches, spiders or dragon flies | | | | of parents spares the space and nutrition. Immortals |
| with size of one metre (3 feet). Going back in time | | | | can die form accidents only. It is too long for children |
| we find shells of enormous molluscs. Many things | | | | to expect a vacancy.Then, having more offspring |
| imply that bigger animal with unstoppable growth | | | | automatically means having more mutations (by mere |
| have a lot of advantages compare to small ones. | | | | number of events). Having more mutations means |
| New species often evolve in their size. An example is | | | | more probability for adaptation to the new |
| growth acceleration in humans. Females prefer taller | | | | environment.Immortal multicellular organisms, even if |
| mates that lead to taller children. Shorter plants | | | | they existed in the past, were quickly wiped out by |
| usually cannot compete with the taller forms in the | | | | accidents and overgrown by mortal multicellular |
| wild. A short mutant in a patch of tall plants would be | | | | organisms.Again all this is just a hypothesis. |
| shaded outMechanism of reproduction was also | | | | |