The science world went into shock late last year when it was announced two baby girls had been born in China — after their DNA had been “edited”.

It’s an ethically incomprehensible act: we simply don’t know enough about the gene editing technique CRISPR or how DNA works to experiment on human children. There could be unanticipated side-effects.

It appears exactly that may have happened.

The twins, named Lulu and Nana, had their genes edited while still embryos to give them a level of HIV resistance, the virus that causes AIDS.

But new research has found the specific gene deleted to provide this immunity — CCR5 — has multipurpose functionality.

Experiments with mice have linked it to suppressed intelligence. And other studies suggest it may affect human performance at school, and in recovery from stroke.

“The answer is likely yes, it did affect their brains,” Alcino J. Silva, a neurobiologist at the University of California, Los Angeles, told the MIT Review.

“The simplest interpretation is that those mutations will probably have an impact on cognitive function in the twins.”

In this case, the experiment is likely to have enhanced the girls’ cognitive abilities.

Chinese scientist He Jiankui had intended to surprise a world biological science forum last year with the announcement of the birth of the first gene-edited humans.

He certainly achieved that.

News of his work was revealed days before his presentation by the MIT Review, sparking international outcry. Mr He and his team are currently under investigation by his Chinese university for ethical breaches.

While Mr He had declared his intention to improve the girls’ HIV resistance, no mention was made in his work of a desire to also boost their intelligence.

Exactly what impact the gene editing experiment has had on the girls will not be known until they are much older.