Thursday, June 09, 2005

On ageing and on death

Ageing and death due to ageing is a characteristic that is not mandatory in all life forms. In fact bacteria and other living entities who reproduce symmetrically do not age since the "mother" entity splits into two twin entities that can't be identified as the mother and the child. This means that these basic life forms must ensure they do not age and thus once they duplicate they are as viable as they were when they were born from a previous duplication.
Mammals and other higher forms that developed the capacity of creating multi-cellular organisms do age and this is not a problem since the degradation affects only the mother, the children are born with their "age counter" at zero.

The interesting points here is why do we have to die and what would happen if we didn't.

We must die because pluricellular organisms are immune to mutation and thus to natural selection, only our species can evolve but the individuals do not. Unlike unicellular organisms, mutations on higher organisms will happen only in one cell, one tiny piece of ourselves and this mutation will not propagate to the rest of the being. This means that once we are born our species has bet on us and counts on us to have as many descendents as possible, prove the fitness of our genes and then die, leaving behing our progeny to continue the evolution/selection process.

If you consider two species of mammals, one living indefinitely and the other with a limited life span (probably fine-tuned by natural selection) a computer simulation will show that the limited-life span species will have a faster response to evolution and thus will more quickly adapt to changes in environment as well as double cross the other species in competition.
The other species, the one with immortal individuals will face two problems: the first is that since the elders do not die and they have more experience/resources than the youngsters they will keep the monopoly of the habitat's resourses and will kill the youngsters by hunger. The second point is that their presence will delay the evolution of the species since archaic genomes will continue to mix with newer ones generated by mutation and meiosis crossing.

In the next article we'll talk about why this process created by natural selection is useless in human beings and we'll also trace a link between cancer, development and ageing.


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