Three-Parent Babies: It's More Messy Than we Thought

IN A few weeks, the UK is set to decide whether to become the first country to allow the creation of "three-parent babies". The government's scientific advisers are urging a yes vote, but the debate will be bitter and divisive. Opponents argue that the technology is not ready. It now seems they may be right – albeit for the wrong reasons.

The debate concerns a technique called mitochondrial replacement. Designed to prevent diseases caused by mutations in the mitochondria – the cell's power packs – it uses donor mitochondria to replace the mother's faulty ones. Hence the "three-parent" tag: mitochondria have their own genome, so the child ends up with genes from three people.

Proponents argue the name is misleading: mitochondria and their genomes are purely functional, limited to producing energy and exerting no influence on appearance, personality, intelligence or other human attributes that we value.

Now it appears that we may have seriously underestimated the influence that mitochondria have. Recent research suggests that they play a key role in some of the most important features of human...