https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1644264/pdf/procrsmed00338-0007.pdf
Death Squared:
The Explosive Growth and Demise of a Mouse Population
by John B Calhoun MD
(Section on Behavioral Systems, Laboratory of Brain Evolution & Behavior, National Institute of Mental Health, 9000 Rockville Pike, Bethesda, Maryland 20014, USA)
I shall largely speak of mice, but my thoughts are on man, on healing, on life and its evolution. Threatening life and evolution are the two deaths, death of the spirit and death of the body. Evolution, in terms of ancient wisdom, is the acquisition of access to the tree of life. This takes us back to the white first horse of the Apocalypse which with its rider set out to conquer the forces that
threaten the spirit with death. Further in Revelation (ii.7) we note: 'To him who conquers I will grant to eat the tree' of life, which is in the paradise of God' and further on (Rev. xxii.2):
'The leaves of the tree were for the healing of nations.'
This takes us to the fourth horse of the Apocalypse (Rev. vi.7): 'I saw … a pale horse, and its rider's name was Death, and Hades followed him; and they were given power over a fourth of the earth, to kill with the sword and with famine and with pestilence and by wild beasts of the earth' (italics mine). This second death has gradually become the predominant concern of modern medicine. And yet there is nothing in the earlier history of medicine, or in the precepts embodied in the Hippocratic Oath, that precludes medicine from being equally concerned with
healing the spirit, and healing nations, as with healing the body. Perhaps we might do well to reflect upon another of John's transcriptions
(Rev. ii. 1): 'He who conquers shall not be hurt by the second death.'
Bodily Mortality
Let us first consider the second death…
…Conclusion
The results obtained in this study should be obtained when customary causes of mortality become markedly reduced in any species of mammal whose members form social groups. Reduction of bodily death (i.e. 'the second death') culminates in survival of an excessive number of individuals that have developed the potentiality for occupying the social roles characteristic of the species. Within a few generations all such roles in all physical space available to the species are
filled. At this time, the continuing high survival of many individuals to sexual and behavioural maturity culminates in the presence of many young adults capable of involvement in appropriate species-specific activities. However, there are few opportunities for fulfilling these potentialities. In seeking such fulfilment they compete for social role occupancy with the older established members of the community. This competition is so severe that it simultaneously leads to the nearly total breakdown of all normal behaviour by both the contestors and the established adults of both sexes. Normal social organization (i.e. 'the establishment') breaks down, it 'dies'. Young born during such social dissolution are rejected by their mothers and other adult associates. This early failure of social bonding becomes compounded by interruption of action
cycles due to the mechanical interference resulting from the high contact rate among individuals living in a high density population. High contact
rate further fragments behaviour as a result of the stochastics of social interactions which demand that, in order to maximize gratification from social
interaction, intensity and duration of social interaction must be reduced in proportion to the degree that the group size exceeds the optimum.
Autistic-like creatures, capable only of the most simple behaviours compatible with physiological survival, emerge out of this process. Their spirit has died ('the first death'). They are no longer capable of executing the more complex behaviours compatible with species survival. The species in such settings die.