User:Jtwsaddress42/Projects/Project 2/Sections/Chapter 4/Senescence & The Purpose Of The ''Soma''

Individuals are selected, species evolve. That is the relationship between the individual phenotype exemplified by the Soma or somatic line; the species genome, or gene pool, which resides in the Germ or germ line; and, what we mean by the word "evolution" in a biological context.

Ultimately, Buss explains, in early animals, as the early animal body plan complexifies, the openness of the germ line to developmental variation in the course of embryogenesis becomes more refractory; and the only way that the body plan can continue to complexify is for the germ line to be sequestered so as to protect its own genomic integrity between recombination events. Clonal replication is directed into the soma such that the soma protects the germ line from destabilizing influences. At this point the soma, or body, has essentially become a protective transport mechanism for the germ line through the environment until such time as the germ line can consummate a successful sexual recombination and progeny.

Cells of the soma are under pressure to differentiate, specialize, and forgo reproduction. To achieve this, cellular populations exert mutual reproductivity-inhibiting mechanisms on the neighboring cells in their community - and instead, direct them along a specialization trajectory that is the result of somatic selection during the developmental sequence.

Essentially the body is a spaceship for the germline, where the cells of the body forgo their ancient impetus towards reproduction via binary fission, and instead differentiate and participate in the communal activity of protecting the species germ line from environmental damage and mutation - thereby, protecting the species genome from deleterious mutations to the course of developmental ontogeny.

For animals, the soma, or body is meant to be discarded - it is for the good of the species integrity. The accumulation of physical damage, and environmental mutation, is discarded with the soma; and, the genome of the species is protected from the potential destabilizing effects it would have had on the developmental program already established. Most unicellular organisms can be killed, but they don't die of old age - they divide. For metazoans, the soma is the origin of mortality - and, the inevitability of death in animals. This is the cost of being a true metazoan.

The old age senescence of the soma is adaptive - and, meant to prevent the introduction of mutation into the species gene pool. These cell have sacrificed themselves for the good of the species, which is carried in the germ line. It is no surprise that pre-programmed cell death and apoptosis occur within the developmental ontogeny, selection is for the benefit of the germ line and any benefit to the soma is incidental.

Interestingly, cells that disengage from the inhibitory mechanisms on reproduction within the soma, can become cancerous as they resort to their ancestral pattern of reproductive fission with a complete disregard to the physiological and adaptive integrity of the body they are embedded within.