Changes to one part of a complex system can lead to dramatically different changes in other parts.

While gene drive technology has only been used in small trials so far, the potential for far-reaching unintended consequences is enormous. This gene technology could remove whole species from ecosystems. Which could be great for tackling problems like malaria.  But wiping out species in the past has had its problems. The extermination of sparrows in China from 1958 to 1962 resulted in severe ecological imbalance and widespread famine, and acts as a cautionary tale.

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