Evolution works because of the differential reproduction of individuals with certain features. If an organism has a harmful gene, it will not survive to reproduce and will perish before it produces offspring.
To some extent this is true for human beings as well, although we usually see it as a personal tragedy rather than as a force of nature. Infertility may be Nature’s way of decreeing that this man or this woman, or this couple, are not “fit” in the evolutionary sense.
So surely IVF, which enables people to bypass their infertility, must be having an effect upon human evolution.
This tricky but important question was tackled by Norwegian scientists in a recent article in the journal Human Reproduction. “Assisted reproduction is redefining human society and biology and, in the face of profound ethical issues, it is important to understand the technical and conceptual principles that underlie this new paradigm,” they write.
They point out that IVF systematically changes selection pressures, involving “a combination of artificial environments and selection criteria that are distinctively different from those of natural reproduction”.
They give a number of examples. For instance, the human oocytes, or eggs, which survive the selection process are different. The follicles in the ovary of normal eggs are highly sensitive to the FSH and LH hormones; IVF eggs, on the other hand, can survive harsh laboratory conditions, including puncturing it to insert a sperm in some procedures.
IVF favours sperm that swim fast for a short distance while nature “favours long-distance swimmers that are able to navigate the female reproductive tract”.
IVF embryos have to survive contact with plastic surfaces, exposure to light, mechanical manipulation, living in culture media in a Petri dish and abrupt temperature changes. There may be differences in how IVF embryos survive implantation and miscarriage.
Even the couples who seek out IVF come from a distinct subgroup: “Overall, the limited availability of IVF favours healthy sub-fertile couples in stable relationships who live in high-income societies over other sub-fertile couples”.
The authors stress that much of what they say is speculative, but they conclude that “The most extreme evolutionary scenario is a subpopulation in which reproduction is entirely dependent on IVF … Overall, it seems clear that IVF facilitates the propagation of genetically heritable traits of sub-fertile couples, and we suspect that ongoing studies of IVF offspring will show an increased risk of subfertility for this group.”
Apart from allowing infertile people to reproduce, IVF may also select for traits such as, for example, a resistance to exposure to plastic surfaces. What the results of this will be is completely unknown.
Other recent papers in the same journal point out that the Petri dishes in which IVF embryos spend the first days of their lives are filled with mysterious fluids made up of unknown ingredients. The composition of these laboratory cultures affects the birthweight of the resulting babies – and possibly their long-term health.
These alarm bells are not being rung by moralizing criticis. In a blistering editorial, Hans Evers, the journal’s editor, admitted that he knows far more about the ingredients in his favourite peanut butter, from the ingredients to the production record, than he does about embryo culture media.
“It’s not possible to sell a single drug on the market if you do not give the total composition of the drug, but for such an important thing as culture media, that envelopes the whole embryo, you can sell it without revealing its contents. For me, that’s unacceptable,” Evers told New Scientist. “Compared to the rest of medicine, this is such a backward area. We can’t accept it any longer.”
A working group of the European Society of Human Reproduction and Embryology, led by Professor Arne Sunde, from the University Hospital in Trondheim, Norway, has found that culture media for IVF embryos vary widely, their composition is usually unknown by the end users (the embryologists, clinicians and patients), and data about the influence of the media on embryos are conflicting.
“We have no information about long-term consequences of this, but we cannot rule out that the composition of the culture media may affect the health of children as they grow up and become adults,” says Dr Sunde.
One possibility is an epidemic of chronic disease.
This is what the “the Barker Hypothesis” suggests. This idea stems from observations of the health of Dutch children conceived during a severe five-month-long famine in the German-occupied part of the Netherlands in the winter of 1944 to 1945. It was a perfect experiment – albeit a tragic one – in the effect of gestation on adult health. In middle age these children of starving mothers are suffering from obesity, dementia, hypertension, coronary heart disease, and diabetes. The results may very well be relevant to the harsh and unusual environment of the Petri dish.
So while an IVF baby may be a delight to cuddle, 50 years later an IVF adult could be an overweight, doddering, diabetic, stroke-prone candidate for a heart attack. The millions of IVF children now alive may be health time-bombs.
We don’t know. The first IVF baby, Louise Brown, is only 38. Unfortunately, IVF scientists have been turning a blind eye to these issues for 38 years.
Back to the Norwegian scientists’ musings about IVF and evolution. Let them have the last word. They conclude, somewhat ominously, that despite IVF’s success in producing babies for infertile couples, it makes reproduction increasingly dependent upon artificial means: “It is our opinion that IVF should be seen as a primary example of how the human species is becoming not only culturally —but also biologically— dependent on our own technology.”
Michael Cook is editor of MercatorNet.