To David Jean Dryer

https://barryhisblog.blogspot.com/2026/01/to-david-jean-dryer.html

A little bird told me that someone had posted the following comment.

Barry the idea that an ancient virus infected a common ancestor of chimps and humans goes against the scientific principle of the most direct simplest explanation.
The comment
1.the virus had to infect no just any cell but a germ cell the most guarded of all cells.
2. the virus had to not kill the germ cell as a virus is programed to do
3. the virus had to become harmless losing the genes for building viral proteins.
4. the virus had to retain the promotor genes that no longer had any viral genes to promote.
5. the viral promotor gene had to be coopted into the human genome so that the human genome could not properly function without the coopted viral genes.

A. This means that humans are as much a product of viruses as of biological evolution. B. This means that all 8% of the human genome that are LTRS must be of viral origin, not just the 6-8 originally postulated.
C. LTR promotors are found in all living things so not just humans but all life is essentially viral in origin.
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My reply

1. Viral infection takes place on a massive scale. Even if germ cells are the "most guarded", viruses get through. See 2.Q
2. Viruses do not aim to kill. They aim to induce the host cell to make viruses. The death of the cell is a common end result, but not a necessary one. Think parasites. It is not in their interests to kill their hosts before benefiting from them. Reverse transcription is an error-prone process. No error detection, and certainly no error correction, so integrations can already be damaged and replication incompetent. In fact, we can easily fix some of them and recreate the original retrovirus, fully functional. Retroviruses can and do infect germ cells. The plainest proof of this is KoRV, the koala retrovirus. It exists in both exogenous and endogenous forms. It has endogenized at different loci in different koalas. Not at all in others. Endogenization is the only explanation for this.
3. Reverse transcription errors only have to incapacitate viral proteins. And not necessarily all. Any error would be likely to incapacitate viral replication. 
4. See 3.
5. Drop a promoter anywhere in host DNA and there is a good chance it will promote something already there. Genes exist that already have multiple promoters. The addition of more is just more promotion.

A. Viruses can be a source of variation - fuel for biological evolution.
B. 8% of our nuclear DNA is of viral origin. 90% of which is composed of solo LTRs. 10% of which is more than solo LTRs, partial or complete but damaged provirus remains.
C Retroviruses prey on all sorts of living things. LTR promoters are to be expected. To say that all life is essentially viral in origin is out of the blue nonsense, not supported by anything that either the commenter or I have said. I can't see why the commenter said that.


Tagging David Jean Drayer & Lydia P. Lathemis.