"At the very outset, we have an unsolicited advice for scientists Peter Kristensen and Tor Bjerkedal. The duo would do well to keep their study on siblings and intelligence within rarified confines of the academic world because the results can spark off a Darwinian battle between forst and second/third born children." Please explasin the meaning of phrases in bold.
rarified confines - distant from the real world
Darwinian battle- a fight to survive, where the fit win