Homo sapiens liberatus

It is well known for a long time that genomes contain numerous biological programs. The great majority of them are useful and even quite necessary for the organism. However, some genetic programs are obviously counterproductive for the individual. In certain cases, their operation results in the death of the organism. By analogy with apoptosis and mitoptosis (programmed elimination of cell and mitochondrion, respectively), programmed suicide of organisms can be defined as phenoptosis. For organisms that reproduced only once, death usually occurs soon after reproduction is over, being in animals sometimes the final step of copulation. Such an event can be exemplified by the death of bamboo in the middle of the summer immediately after formation of seed, as well of Arabidopsis thaliana on day 25 of life, also when formation of seeds is completed. In the latter case, removal of seeds prevents the death so that the plant can survive for many months. Similar relationships were shown in soy. An attempt was undertaken to identify a lethal poison that is produced by soy beans. It proved to be an organic acid of unusual structure. Again, removal of beans greatly prolongs the lifespan of soy, which is converted in this way from annual to perennial plant. Ejaculation of the male praying mantis occurs only after his decapitation which is carried out by the female at the very end of copulation. The male Australian marsupial mouse dies two weeks after the rut, being poisoned by his own pheromones that attracted females during the rut. The evolutionary advantage of such dramatic events is rather clear. Death of one of the parents (sometimes even both of them, as happens, e.g., in certain squids) results in an increase in diversity of progeny, an effect certainly increasing evolvability of the species. Males of the marsupial mouse or praying mantis can play the role of father only once in life, so the next litter of the same female will require another father.
There is much evidence that programs favorable for evolvability but counterproductive for the individual exist also in repeatedly multiplying organisms. Senescence of organism seems to be one of the most important cases of this kind. Concerted decline of many physiological functions with age may be regarded as slow phenoptosis. This process also increases evolvability due to the fact that the pressure of natural selection on an organism rises when this organism becomes weaker and weaker due to progression of senescence. A new small trait that is not essential for survival of a strong young individual may appear essential (and hence, can be recognized by evolution) in weak old individual.
Impressive examples of phenoptotic programs have been found in studies of interactions of animals with pathogens. In rats, a protein is present in the blood that recognizes the plague bacterium and, after such recognition, induces septic shock killing the infected animal before it passes infection to all its relatives. Septic shock is operative also in humans, but the rat-type protein is replaced by a less efficient one. As a result, phenoptosis appears to be much slower, and pandemic becomes possible. This is why rats rather than humans serve as a reservoir of plague infection.
There are some reasons to assume that both other animals and humans have a special phenoptotic program preventing uncontrolled genome modifications under conditions of severe stress. Apparently, there are sensors monitoring the level of certain crucial parameters changing under stress conditions. If deviations of these parameters from normal appear to be larger than some critical level, a signal for "biochemical suicide" is generated. As a result, the ill individual dies even if the crisis is over. Perhaps, an example of this situation was quite recently described by Carl Hauser (see his abstract). It was found that receptors recognizing bacterial DNA (or formyl methionine, which is specific for bacteria) and inducing sepsis can be actuated by mitochondrial DNA and formyl methionine originating from mitochondrial proteins. Large trauma always results in appearance of these mitochondrial compounds in the blood, entailing a syndrome quite similar to septic shock. A possible physiological function of this mechanism is to beat completely an individual weakened by a large trauma ("enemy within", C. Hauser) and, hence, to purify the population from such organisms becoming a burden for the community. Interestingly, buffalos solve the same problem by allowing lionesses to follow the herd in its rear guard, to kill those buffalos that constantly remain behind the others.
Generally speaking, any contradictions between interests of genome evolution and individual are solved in favor of the genome, a rule increasing evolvability. However, humans no more rely on their evolution, which is too slow and unpredicted. If they need to fly, they construct a plane instead of waiting for millions of years for a moment when wings occasionally appear on their back. This is why programs that were invented by evolution to increase evolvability but proved to be counterproductive for the individual have no more sense for humans, who should try to abolish such atavisms. Senescence, septic shock, mechanisms of sudden death at the moment when a crisis is, in fact, over this is an incomplete list of "enemies within" It seems possible that the list should include cancer if this disease represents a program eliminating an organism with large mutational load.
In any case, it seems obvious that cancellation of genetic programs counterproductive for the human organism would be the great achievement of XXI century biology and medicine. This will mean prolongation of youth and disappearance of age-related diseases. Such an event will be a sort of "Rise of the machines" to stop genome tyranny and to convert Homo sapiens into Homo sapiens liberatus.

Homo Sapiens Liberatus Workshop, Moscow State University, May 2010

www.programmed-aging.org

 

V.P. Skulachev