Engineering our biological destiny
EXTRACT: Whereas all previous evolutionary innovation has relied on the slow and wasteful process of natural selection, mankind will soon be able to engineer his own biological destiny. This will eventually lead to an end to cancer, heart disease and even perhaps that most intractable of genetic diseases: death itself.
Dipping into our gene pool
The Guardian, 7 October 2008
*Steve Jones paints a gloomy picture of human evolution at the end of the line but you could argue that it's only at the beginning
Steve Jones paints a gloomy picture of human evolution at the end of the line with only gradual homogenisation towards universal brownness to look forward to. But in fact we are likely to be soon entering the most dynamic period of evolution one in which humans will be able to transform their own biology by genetic engineering and gene therapy. Whereas all previous evolutionary innovation has relied on the slow and wasteful process of natural selection, mankind will soon be able to engineer his own biological destiny. This will eventually lead to an end to cancer, heart disease and even perhaps that most intractable of genetic diseases: death itself.
It is easy to imagine situations where genetic modification to produce so-called designer babies could be considered to be a good thing. In the UK, about one in 33 babies are born with a genetic disease. Some of these will be relatively mild conditions but many, like cystic fibrosis or muscular dystrophy, will be terminal or severely debilitating. It is now possible, using pre-implantation genetic diagnosis (PGD), to examine an embryo generated by IVF and detect the presence of the defective gene. This is currently performed in a number of centres in the UK and elsewhere for parents of children born with a genetic defect who have a high chance of bearing a second child with the same or a related defect. PGD allows parents to choose whether or not to implant an embryo into the woman's uterus. Clearly, if the embryo carries a fatal gene defect then most parents will choose not to have it implanted into the womb.
Currently, this form of selective implantation is all that is available to parents. But scientists may soon have more to offer. Considerable progress is being made in research designed to correct genetic defects in affected children, so-called gene therapy. In these approaches, a copy of the healthy gene is introduced into the cells of the patient in the hope that it will replace or complement the defective gene. Some success in this approach has been reported, particularly for patients with the blood disease haemophilia. But huge challenges remain. The main problem is delivering the new healthy gene to enough cells in the child's body. This task would be far easier if the number of cells was very small, for instance in an embryo.
Modifying heritable genes is presently considered to be unacceptable, at least in humans, because we would be tinkering with our genetic inheritance. But is that such a bad thing? Our genes are the products of billions of years of evolution chance mutations that were selected because they provided an advantage to one or more of our ancestors. But sometimes, random mutations can damage our genes. If that damage is in a skin or muscle cell then it won't be a problem (at least not to our children). But if the damaged gene is in an egg or sperm cell that our children will inherit the damaged gene and may suffer a genetic disease. If they have children (perhaps before knowing they are carrying a genetic defect) then their children may also be afflicted. Given enough evolutionary time, it is likely that unchecked natural selection would eventually remove damaged genes from the population; but should we wait that long? Thousands of children are born each year with defects, such as heart problems, that we have no hesitation in correcting. If we have the technology to correct defects in their genes then isn't it in the interests of the common good to do so?
Gene therapy of human genetic diseases in affected embryos is almost certainly within reach. The team that gave us Dolly the sheep also generated Polly the sheep, the world's first transgenic animal, in 1997. Polly's DNA was engineered, while she was still an embryo, to contain a copy of a human gene. It is likely that similar approaches could be used to correct gene defects in human embryos.
But why should we stop with deadly diseases? Wouldn't you want your children to also have a longer life with lower risk of cancer or heart disease? With more genes linked to common diseases turning up every day, it won't be too long before gene therapy is available to screen out even common ailments. If the technology was available to ensure that your children lived their lives free of cancer, wouldn't you take it?
But what will be the long-term consequences of dipping into our own gene pool? Like all innovations, it's hard to say. Modern domestic dogs are all descended from the wolf by a process of purely artificial selection. Add to this genetic modification and the results could be remarkable. Perhaps the people of the future will be as different from us as we are from our primate ancestors. Human evolution is only at the beginning!