VIEW 13
Hedges and diversity
Picture yourself on a bright summer day. There is not a cloud in the sky, but it is still raining—raining DNA, that is. The pollen count is huge, bad news for hay fever sufferers, but also from a biological perspective incredibly wasteful. Only a tiny amount of this genetic material will actually fertilize something. Many plants can reproduce asexually, causing biologists to ponder, “What is the point of sexual reproduction?”
The question was answered in the late 1970s by W.D. Hamilton with his “Red Queen Hypothesis” and computer models of artificial life. He showed that asexual clones were incredibly successful in the absence of infection, but sexual reproducers won because their greater genetic diversity gave them resistance to viral attack. In Alice’s Adventures in Wonderland, the Red Queen must keep running in order to stand still.
Likewise, life is a constant struggle between organisms and viruses, each one evolving to counteract the other, so, in effect, they are running to stand still.
Hedgerows also demonstrate this concept. Neat suburban hedges are made of identical plants propagated by cuttings from a garden center. So, a suburban hedge is a row of single species clones. But a hedge in the countryside has a wider variety of species and has survived longer, as proven by Hooper’s Rule: count the number of species in a 30-meter stretch and multiply by 100 to get an estimate of its age. The photo shows the hedge outside the village church in Chiddingstone, Kent, UK. There are five different species in a 30-meter stretch: hawthorn, field maple, yew, oak, and blackthorn. This would imply that the hedge is 500 years old, which tallies well with the local historical records.
The idea that “genetic diversity grants viral resistance” has recently been adopted in the cyber realm. Professor Michael Franz at the University of California began looking at ways to introduce a form of genetic diversity into computer application programs. With popular desktop software, like the Windows operating system or the Firefox web browser, every copy installed on millions of PCs around the world is an identical clone of the master copy. Could something similar to sexual reproduction create resistance to viruses in software too?
Software is written in a high-level language, like C++ or Java, but must be “compiled” into machine code in order to run. Compilers are set to optimize speed in the resulting code. As a crude analogy, it’s a bit like asking a translator to convert some text from French to English but to only use a limited English vocabulary with no words longer than five letters.
Of course, there are many different ways that a French text could be translated into English; the meaning would be the same but the actual words would be very different once you relax the five-letter limit. It is the same when compiling computer code. Once you are prepared to relax the speed requirement, each compilation can be different from its predecessor. It may run a little slower, but it will be a unique instance of that program, different at the binary or “genetic” level from its parent.
Though this approach is yet to be commercialized, it suggests a promising path to a whole new way of protecting systems from viruses.
