I was thinking similar. It may have well been developed before, but it was either not reproduced by choice, or perhaps could not actually be reproduced.
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"You know how parents tell you everything's going to fine, but you know they're lying to make you feel better? Everything's going to be fine." - The Doctor
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"You know how parents tell you everything's going to fine, but you know they're lying to make you feel better? Everything's going to be fine." - The Doctor