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There is no evidence in the sources reviewed here that Lulu or Nana had enhanced memory, learning, or intelligence. The 2019 claim was a possibility inferred from research on CCR5 in other contexts—not a cognitive result measured in the twins.
What was edited, and why?
In November 2018, researcher He Jiankui announced that he had edited embryos at the CCR5 gene and that twin girls, referred to as Lulu and Nana, had been born. The stated aim was to reduce the possibility of HIV infection. A contemporary Nature Medicine editorial described the births as the first reported result of human germline editing and argued that the work lacked the safeguards needed for clinical use.
The reported edits were not a simple, uniform copy of a naturally occurring CCR5 variant. Commentary on the data described mosaicism—different cells in an embryo carrying different genetic changes—and reported an unintended edit elsewhere in at least one embryo. Those qualifications make it misleading to describe the intervention as a predictable, complete change or as proven HIV protection.
Why did anyone suggest the edits might affect the brain?
CCR5 is discussed not only in relation to HIV entry into cells, but also in research on brain plasticity and cognition. A 2019 article connected those findings, including work in animals, to the twins’ reported edits and raised the possibility of cognitive effects. That was an extrapolation from other research, not a finding about the girls.
Even if CCR5 has a role in brain processes, results from other models or contexts cannot establish what an embryo edit did in these children. The article’s suggestion was therefore a hypothesis about a possible unintended effect—not evidence that either twin’s cognition was enhanced.
What evidence is available about the twins’ cognition?
The sources reviewed here do not report direct measurements of either twin’s memory, learning, intelligence, or school performance. They also do not provide a primary clinical dataset that would allow readers to assess a cognitive effect. The distinction is important:
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| Evidence category | What it establishes |
|---|---|
| Reported embryo edits | CCR5 was targeted, but commentary described mosaicism and an unintended edit in at least one embryo; this does not establish a uniform, predictable change. |
| Research on CCR5 in other settings | It supplied a basis for discussing a possible connection to brain plasticity or cognition, but it does not show what happened in the twins. |
| Direct cognitive measurements in Lulu or Nana | No result is reported in the sources reviewed here. |
Because direct follow-up is not established in these sources, neither enhancement nor a lack of any cognitive effect can be concluded from them. No statistic in this reporting should be treated as a measured cognitive effect in the children.
What did the case raise about ethics and oversight?
A 2019 Nature Medicine editorial said germline editing was not ready for human clinical use, particularly without more rigorous laboratory testing. It called for predefined endpoints, responsible recruitment and oversight, long-term follow-up, and an international registry. Those safeguards matter in part because genetic changes made to embryos can affect the resulting children and may be heritable.
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Later scrutiny also raised separate concerns about consent and ethics review. An ethical analysis of the consent materials and related documents identified serious ethical concerns. In a clarification to its 2019 report, Nature said a Guangdong health-ministry investigation found the claimed ethics approval was fake. That finding about approval should not be conflated with bioethicists’ separate assessment of whether consent was valid.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.What can readers responsibly conclude?
The brain-enhancement claim described a plausible concern drawn from research outside the twins, not a demonstrated outcome. The available sources establish that CCR5 was targeted for a stated HIV-related purpose and that the reported edits had important limitations; they do not establish a cognitive benefit or provide direct cognitive follow-up.
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