The sexual shuffling of the genes in a gene pool could be regarded as a kind of borrowing or sharing of genetic 'ideas', but sexual recombination is confined within one species and is therefore irrelevant to this chapter, which is about comparisons between species: for example, comparisons between marsupial and placental mammals. Interestingly, high-level borrowing of DNA is rife among bacteria. In a process that is sometimes regarded as a kind of precursor to sexual reproduction, bacteria - even quite distantly related strains of bacteria - swap DNA 'ideas' with promiscuous abandon. 'Borrowing ideas' is indeed one of the main ways by which bacteria pick up useful 'tricks' such as resistance to particular antibiotics.
The phenomenon is often called by the rather unhelpful name of 'transformation'. That's because, when it was discovered in 1928 by Frederick Griffith, nobody understood about DNA. What Griffith found was that a non-virulent strain of Streptococcus could pick up virulence from a completely different strain, even though that virulent strain was dead. Nowadays we would say that the non-virulent strain incorporated into its genome some DNA from the dead virulent strain (DNA doesn't care about being 'dead', it is just coded information). In the language of this chapter, the non-virulent strain 'borrowed' a genetic 'idea' from the virulent strain. Of course, bacteria borrowing genes from other bacteria is a very different matter from a designer borrowing his own ideas from one 'theme' and re-using them in another theme. Nevertheless, it is interesting because, if it were as common in animals as it is in bacteria, it would make it harder to disprove the 'designer borrowing' hypothesis. What if bats and birds behaved like bacteria in this respect? What if chunks of bird genome could be ferried across, perhaps by bacterial or viral infection, and implanted in a bat's genome? Maybe a single species of bats might suddenly sprout feathers, the feather-coding DNA information having been borrowed in a genetic version of a computer's 'Copy and Paste'.
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