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J R Soc Med. 2005 March; 98(3): 134–135.
PMCID: PMC1079424

Human endogenous retroviruses in health and disease

Symbiogenesis certainly removes the scientific straitjacket from the purely darwinistic interpretation of evolution.1 It recognizes that cooperation is a strong developmental principle. Fred Hoyle, in his 1983 Lloyd Roberts Lecture at the RSM,2 commented on the prevailing confusion whereby 'evidence for evolution has become misinterpreted as evidence for Darwinian theory'.

Frank Ryan3 suggests that about 50% of the human genome is a legacy of human endogenous retroviruses (HERVs) and their fragments. These have invaded as exogenous viruses throughout the 4 billion years of biological history and have remained intracellular to become symbiotic viruses permanently transmitted vertically. Many of the thousands of HERVs in each cell have brought with them useful or even essential biological functions such as the formation of syncytium of the human placenta. Without the ERVs humanity would not survive.

What is the origin of these exogenous retroviruses, and for that matter bacteria, which seem to have become mitochondria in the protozoan stage of development? Hoyle presented astrophysical evidence that the content of comet efflux was remarkably lifelike. He noted Delsemme's analysis4 of the ratios of oxygen, hydrogen, carbon and nitrogen in the comet efflux, which were O : H : C : N= 1 : 1.8 : 0.32 : 0.08. After much searching he found the ratios for dried bacteria to be the best biological match—1 : 2.2 : 0.5 : 0.05. No other celestial body had anything like this composition. Furthermore Hoyle presented strong statistical arguments for the impossibility of chance creation of our 2000 or so enzymes for natural selection to choose from—a figure he puts at 1 in 1040 000, 'which is more than all the atoms in all the galaxies that we know of'.

In 1986 Hoyle became more specific5 observing that the periodicity of pertussis infections every 3.5 years is the same as the orbital periodicity of comet Enke. The earth crosses the streams of particles from comet Enke on 20 October to 25 November and from 23 June to 7 July each year. Also the great flu epidemics have occurred when comet Enke has been nearest to Earth. As Ryan points out, there is little doubt now that viruses and viral fragments contribute hugely to our genome. The only question is where do they come from? Hoyle made a strong case for certain comets and suggested a space probe to comet Enke. NASA has just announced a deep impact mission to comet Tempel I. It may be that all comets do not contribute to this viral and bacterial effluence. We should know within a few months whether comet Tempel I does.


1. Fox R. Symbiogenesis. J R Soc Med 2004; 97: 559. [PMC free article] [PubMed]
2. Hoyle F. From virus to cosmology. J R Soc Med 1983; 76: 99-110 [PMC free article] [PubMed]
3. Ryan F. Human endogenous retroviruses in health and disease; a symbiotic perspective. J R Soc Med 2004; 97: 560-5 [PMC free article] [PubMed]
4. Delsemme AH. In: Ponnamperuma C, ed. Comets and the Origin of Life. Dordrecht: Reidel, 1977
5. Hoyle F. Halley's comet and others: the bacterial starshells. J R Soc Med 1986; 79: 691-3 [PMC free article] [PubMed]

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