Ethically questionable selection of embryos for intelligence genes would bring little benefit.
Vision of the future in the field test: Up to now it has been forbidden to test embryos for “good genes” – this should prevent the breeding of “designer babies”. But what would such a genetic selection do? That’s exactly what researchers have tested. The result: just 2.5 IQ points and 2.5 centimeters in size could be won on average – and even that would not be safe. The optimized human is therefore probably still a lot removed.
Genome-wide association studies (GWAS) allow researchers to better identify the genetic basis for complex, multi-gene-engineered properties. These include many ailments, but also positive traits such as intelligence. This in turn raises the concern that the knowledge of these predispositions could be used in the future also for the creation of genetically optimized humans – for ” designer babies “.
Selection already in the early embryo?
It would be conceivable, for example, that embryos in artificial insemination (IVF) are specifically selected for “good genes” – preimplantation genetic diagnosis (PID) makes this theoretically possible. However, because this raises significant ethical issues, PID is highly regulated in Germany and some other countries and may only be used in exceptional cases, such as severe hereditary diseases.
Even more controversial are targeted interventions in the genome of embryos, as happened in 2016 in China . Researchers had used a human protective gene against HIV for two human embryos using the gene scissors CRISPR / Cas9. The same method could theoretically also be used to genetically optimize children before implanting them in the womb. However, this is still forbidden and methodologically pure future music.
Test on fictional IVF embryos
One question, however, remains open: Would it even be possible to optimize even complex, polygenic features, such as intelligence, with such methods? That’s exactly what researchers around Shai Carmi from the Hebrew University of Jerusalem have investigated – the fictitious example of a selection of embryos for intelligence and body size. Both are polygenic traits, for which one knows, for example, which gene combinations change the trait as much as it does.
Specifically, the researchers wanted to know what concrete effect it would have if a pair of their five or ten IVF-generated embryos would only carry the child who had the best intelligence genes or body size genes. To do so, they combined the genetic material of 102 Israeli couples and just under 1,000 Greek men into fictive pairs and produced ten hypothetical embryos per pair – with similar random combinations of genes as those produced during fertilization.
Then the researchers selected the embryo with the best gene combination for intelligence or height and calculated how much this child would stand out from the average of his siblings.
Only three IQ points – maximum
The result was rather modest: “Under current technology and with five viable embryos per pair, the average benefit would be 2.5 IQ points and 2.5 centimeters in height,” the researchers report. With ten viable embryos – an unrealistic number for today’s IVF procedures – the advantage of such a “designer baby” would be three IQ points and three centimeters.
The researchers said that this effect could not be significantly enhanced even if one pair – for example, by cloning – produced and tested a thousand different embryos. “Our simulations show that the benefit in terms of the desired feature is relatively small,” Carmi and his team say.
Genes are not everything
And there is one more thing to add: “Much of these features are unpredictable,” says Carmi. “Even if someone selected an embryo whose IQ would have to be two points higher than the average, there is no guarantee that it will actually show itself.” In addition to the genes, other influencing factors almost play a role for the intelligence and most other traits equally important role.
In concrete terms, Carmi and his colleagues reviewed the impact of this on a supplementary study with 28 large families with an average of ten adult children. Using DNA analysis, they first determined their polygenic scores for body size and calculated how large the participants would theoretically have to be. They compared this with their actual height.
The result here: Only in seven of the 28 families were the children with the best polygenic score also the largest among the siblings and in five of the families these children were even smaller than the average.
Brings a little and is ethically questionable
According to the researchers, this clearly shows that selecting embryos for intelligence genes or other beneficial polygenic traits would not only be ethically questionable – it would also do little.
Similarly, the human geneticist Markus Nöthen from the University of Bonn sees it. In a commentary he writes: “The study shows very convincingly that the scenario of” designer babies “, where by embryo selection large effects on features such as height or intelligence could be achieved, is unrealistic at the present state of knowledge, but also a little in the foreseeable future probable scenario remains. “