You make several assumptions that are either disputable or clearly not
valid
You propose that an increase in the size of a part of Einstein's brain
is equivalent to variations in size between brains of the same sex and
between males and females. Einstein was exceptional, by definition
therefore he is different from the general population - thus why
should any comparison or conclusions about his brain hold for the
general population? You cannot equate a 15% change in Einstein's
brain to the difference between males and female brains. Histological
analysis of Einstein's brain has revealed a greater number of glia
than controls thus this 15% peculiarity of Einstein's brain may be
totally incomparable to the normal variation in brain size (it could
just be due to abnormally large numbers of glia perhaps). Whose to
say that the difference between the on average larger male and smaller
female brain is simply the density of cells such that both have
similar numbers of neurones and glia in the end anyway (maybe females
have even more!).
You assume Einstein had a high IQ (and this is not trivially correct)
You assume that in the control group, brain size correlated with IQ
which is neither explicitly stated nor a valid a priori assumption as
it is what you are trying to prove. It may indeed have been the case
that IQ did not vary with brain size in any way or was even inversely
correlated, in which case comparing Einsteins brain is not valid.
Einsteins brain represents an exceptional n=1, using which is a very
dubious way of reaching general conclusions about the unexceptional
population
Though the original author is tentative about concluding that the
posterior parietal lobes are involved in intelligence you make the
definitive claim with very little evidence. For instance, Einstein
was also dyslexic - why should the 15% change not be involved with
this disorder and have nothing to do with his genius. For all you
know, Einstein may have had dramatically different neuronal circuitry
which gave him the insight he had, none of which would have been borne
out by the data presented in the article.
