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All creatures great and microscopic: Viruses, DNA, and religious anthropology

When we think of ourselves as human beings, it is often as separate from the rest of our world in some sense. This seems natural enough to most of us much of the time because we are self-conscious. We look out at the natural world and this perspective seems to place us in a privileged – and distinct – position. We are also of course capable of manipulating large parts of our world and this too seems to place "us" over against "nature." Many traditional religious views of what it means to be a human being (“religious anthropology”) reinforce these common-sense understandings by enthroning humanity somewhere between the merely natural and the supernatural realms. Nevertheless, recent scientific discoveries have been disclosing just how deeply integrated into nature we really are.

For instance, we now believe that consciousness is rooted in the brain, that brain development depends on bodily interaction with an environment, that the great journey of biological evolution links us genetically to every living species, and that our bodies persist because of a delicate balance negotiated with the vast microbial ocean that suffuses our planetary biosphere. Human beings seem more a part of nature than ever. And in case we start thinking that we are related only to the friendly bits of nature, biology stands ready to help us toward a more realistic view of ourselves.

A new study conducted by Vladimir A Belyi, Arnold J. Levine, and Anna Marie Skalka published in PLOSPathogens has found something unexpected lurking in the genes of several species of vertebrates, including humans. It turns out that code from the ancestors of four still extant families of viruses – including the deadly virus that causes Ebola – has been hanging out inside the DNA of at least 19 species of animals for millions of years.

It has long been known that as much as 8 percent of the human genome may have originated from viruses. What is unusual about these new findings is that the sequences that have become integrated into animal genes come not from retroviruses, which reproduce by using their host’s DNA, but from RNA viruses, which do not interact with their host’s genes in the same way.

In an extensive comparison of the gene sequences of over five thousand non-retroviruses to the DNA of nearly 50 vertebrate species, Belyi, Levine, and Skalka found “as many as 80 high-confidence examples of genomic DNA sequences that appear to be derived, as long ago as 40 million years, from ancestral members of 4 currently circulating virus families with single RNA genomes.” Nearly all of these sequences come from only two families within the single order Mononegavirales; bornaviruses (which cause deadly neurological disease) and filoviruses (which cause hemorrhagic fevers). The examples were found in 19 different vertebrate species, including humans, lemurs, mice, microbats, wallabies, and zebrafish.

So, as the researchers themselves conclude, “the sources of genetic information in vertebrate genomes are much more diverse than previously suspected.” The implications of this research for religious anthropology are indeed vast. To be a human being is to carry the genetic inheritance not only of our primate cousins, other furry mammalian friends, and even our far distant reptilian ancestry. To be a human being means also to carry the genomic legacy of viruses so distantly related in terms of phylogeny that they are usually not even considered living things at all. Far from our so-called separate existence, the evidence is pointing to our deeply entangled place in the full measure of the complexity of life on our planet.

Some religious believers will likely meet this research with hostility as an affront to the special dignity of humanity. Others however will be in awe of the amazing complexity of our place within and as a part of our world. And, lest we forget, it took the cooperative work of several of the self-conscious micro-ecosystems we call homo sapiens to realize this small part of who we are.

See here for the original study, Belyi VA, Levine AJ, Skalka AM, 2010, “Unexpected Inheritance: Multiple Integrations of Ancient Bornavirus and Ebolavirus/Marburgvirus Sequences in Vertebrate Genomes” PLoS Pathog 6(7): e1001030. doi:10.1371/journal.ppat.1001030

For a more extensive discussion of the findings of this study for a general audience, see here.