That would explain the resemblance of certain humans to lizards.
>
Or the behavioral similarities of others with viruses?
http://www.newscientist.com/article/mg20527451.200-i-virus-why-youre-only-half-human.html
-- "Hige sceal þe heardra, heorte þe cenre, mod sceal þe mare, þe ure mægen lytlað."