There was some decent discussion over at Metafilter when this was brought up [1]. In particular, one poster dug up a journal article about Brooke [2], including

There was some decent discussion over at Metafilter when this was brought up [1]. In particular, one poster dug up a journal article about Brooke [2], including this juicy tidbit in the abstract: "Dental and bone ages are pre-teen, while telomere length and telomerase inactivity suggest a cellular age at least comparable to her chronological age." One poster's interpretation [3] was that "The telomere length means her cells have divided "at least" as much as an average 16 year old's. The fact that she is no larger despite all this cell division means that most of the daughter cells did not survive." [1]: http://www.metafilter.com/82714/The-girl-who-doesnt-age http://www.metafilter.com/82714/The-girl-who-doesnt-age [2]: http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6T31-4VP666B-1&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&_docanchor=&view=c&_searchStrId=937936727&_rerunOrigin=scholar.google&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=2ce790def5bbae1e00df22d2f2b848c1 http://www.sciencedirect.com/science?_ob=ArticleURL&_udi... [3]: http://www.metafilter.com/82714/The-girl-who-doesnt-age#2619243 http://www.metafilter.com/82714/The-girl-who-doesnt-age#2619...