Have it your own way..

No one really knows. I prefer the 'his' story as its history.

" In 1559, the apostrophe appeared in England in William Cunningham's The
Cosmographical Glasse (Parkes, 1993, p. 55). Sixteenth century English printers
developed the mark to indicate omissions, but this convention is not as simple as it might
sound. Initially, the apostrophe was intended to demonstrate the elision of a vowel,
meaning the vowel sound had been omitted, assimilated, or slurred in pronunciation, as in
th' inevitable end, but the apostrophe was also used to indicate a missing letter when the
vowel no longer existed in the spoken form, as in can't (Parkes, 1993, p.55). Not
th
surprisingly, there was much confusion concerning its usage until the middle of the 19
century, when printers and grammarians attempted to devise rules to govern the usage of
apostrophes (Crystal, 1995, p. 203). Despite their efforts, however, much confusion
remains today.   

The use of the apostrophe to denote possession has its origins in Old English, which
frequently attached the genitive singular ending –es to nouns. Hook (1999), points out
that 60% of all nouns in Old English formed their genitive cases in this manner (p. 44); it
is therefore not surprising that the current genitive ending –s has survived in Modern
English. The apostrophe could be viewed as a way in which to mark the deleted vowel –
e of the –es possessive ending, "derived from the Old English strong masculine genitive
singular inflection" (Blockley, 2001, p. 35). Adrian Room (1989, p. 21) provides support
for this view, citing the Old English word for stone, stän, whose genitive form was
stänes.

Hook (1999) maintains, however, that the apostrophe is "a mere printer's gimmick,
doubtless born of the mistaken notion that the genitive ending was a contraction of his"
(p. 44). An invention of mortals, the apostrophe has indeed been subject to human error.
The –es genitive ending,

often spelled and pronounced –ies or –ys in early Middle English, was
confused as early as the thirteenth century with his, the possessive of
he, so that Shakespeare could later write 'the count his gally', and even
expressions like 'my sister her watch' appeared (qtd. in Hook, 1999,
pp. 44-45).

The unstressed pronunciation of the genitive –es seemed to have caused many speakers to
believe they were saying his. This usage presumably caused pronunciation problems and
gender confusion with a noun such as woman or girl, or a plural noun like winners, but
nevertheless was quite common (Hook, 1975, p.160).   The apostrophe became a sort of
"compromise" to indicate either the missing –e in the genitive ending
–es, or the hi of the mistaken possessive indicator his (Hook, 1999, p. 45). "