THE excitement about the human genome is all very well, but I can鈥檛 help
feeling somewhat disappointed. At the root of my problem are those quaint
notions about 鈥渘ature鈥� that pervade Western culture. The Victorians viewed
humans as the pinnacle of evolution. The Romantics thought of nature as pure and
perfect. If you think these attitudes are a thing of the past, just count the
number of advertisements that sell products as 鈥渘atural鈥� and 鈥減ure鈥�.
Yet the picture that鈥檚 emerging of the human genome leaves such illusions in
tatters. Our genome, it turns out, is a mess. Far from being the polished
product of 3 billion years of evolution, humans look more like an afterthought,
hastily flung together when nature realised that walking, talking monkeys were a
jolly good wheeze.
If some creatures have genomes like a racing bike, lean, mean and starkly
functional, ours is more like an old banger, its back seat littered with rusting
old parts that the owner can鈥檛 bear to discard. Worse, it鈥檚 full of the genetic
equivalent of rat droppings鈥攖he parasitical jumping genes that hijack the
cellular machinery and leave behind endless copies of themselves.
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The amazing thing is that it works at all. Of course, it often doesn鈥檛. As a
quick look through a medical textbook will reveal, what can go wrong often does
go wrong. Genetic defects mean that up to a third of fetuses spontaneously abort
early on. Those rusty old parts do come in handy sometimes, though. Our unruly
genome is a rich source of variation, which may be why we evolved so
quickly.
But if nature is an ingenious owner, making use of whatever it happens to
have to hand, it is certainly not a careful one. One surprise finding has been
that some genes are stored right on the ends of chromosomes, in the bits that
gradually get trimmed off as cells divide.
Crazy design? Not at all. It couldn鈥檛 be more natural. These genes are only
lost in older animals鈥攁nd natural selection doesn鈥檛 care what happens to
individuals once they鈥檝e reared their offspring.
Having cracked our messy code of life, we鈥檙e fast acquiring amazing powers.
We might one day clone people, or genetically engineer future generations. Of
all the arguments for and against such things, the least persuasive is that it
is wrong because it is 鈥渦nnatural鈥�. This, of course, is one of the favourite
arguments of those who oppose genetic engineering. Genes from species like
bacteria would never normally end up in plants and animals, they argue.
For these people, one of the facts buried deep in recent papers on the genome
must have been rather a shock鈥攁 bit like discovering that your mother was
unfaithful and your real father is the postman. For it turns out that, as with
so many things, nature invented genetic engineering first. Vertebrates like us
have acquired no fewer than 200 of our genes directly from bacteria. Many of
these genes now play a vital role.
What鈥檚 more, the traffic is two-way. Genes from more complex creatures are
being found in bacteria. And bacteria don鈥檛 hesitate to engage in the microbial
equivalent of bestiality, with quite different species happily swapping bits of
DNA.
Nature turns out to be the ultimate mad scientist, carrying out the wildest
experiments with reckless disregard for the consequences. We, on the other hand,
know better. We can and should be more careful.