Three cheers for the HFEA, which has given the go-ahead for two UK research groups to produce human-animal hybrid cells (or ‘human admixed embryos’) for medical research. ‘Frankenstein’ makes predictable appearances in comments by objecting bodies and cheap media coverage. But one alarming comment I heard quoted described ‘a disastrous setback for human dignity’. Hmmm. Parkinson’s, Alzheimer’s, strokes….? Let’s not tritely labour the point.

Note, however, a frequent remark from the scientists involved. In their attempts to reassure people concerned by such research, and to counter those who deem it a worthy endeavour to morally appoint themselves guardians of non-sentient clusters of cells, they describe the outcome as ‘99.9% human’.

I get uneasy when percentages are banded around in an attempt to reassure. It smacks of advertising, which suggests bad science. Two things:

1) Where does this figure come from? Presumably, it’s based on the relative sizes of the human nuclear and (cow or rabbit) mitochondrial genomes, with a quick tapping of a calculator revealing the human moiety to be over 99.999%. In which case, why not round up to 100% and disregard the animal egg mitochondrial DNA completely?
Because….
2) The mitochondrial DNA is vitally important to nascent embryos – and there’s an awful lot of it in the egg cell. If we instead consider copy number, then the animal mitochondrial DNA component of the admixed embryo becomes highly significant.

So, is the 99.9% figure fed to the public, because it’s the safest fact? But, it still concedes that the thing is a little bit something else, i.e. the purity of the human element has been polluted. And feeds straight into the hands of those who decry genetic determinism, but then in effect invoke it for their own objecting purposes, deeming the presence of rabbit mitochondrial DNA as somehow rendering a human being part rabbit!

Instead of throwing dodgy, unconvincing percentages around that sound like a scientific marketing trick, let’s emphasise that the admixed embryo is not a human being and never will be – because it will never be implanted. There are more apposite ethical considerations here.

Me? I’m 98% chimp, and proud of it.