The entire Septuagint was pre-Christian, and the New Testament quotes from it, including Pentateuch, Psalms, Prophets, etc. Philo and Josephus (both Jews, Philo died before Christ was born) held it in great respect.
http://en.wikipedia.org/wiki/Septuagint
http://en.wikipedia.org/wiki/Septuagint_manuscripts
Having entire ancient manuscripts in one’s hands that date near when the original was completed is always a problem. (If one thinks about Homer, one sees this without all the controversies that accompany anything to do with the Bible.) The first complete Hebrew Bible manuscript we have is relatively late, too.
Nice try!
It’s not whether there were Jewish translations, it whether what the Church now calls the Septuagint is the same as what Jews called the Septuagint before Jesus. It is manifestly not.
From your wiki source:
“Modern scholarship holds that the LXX was written during the 3rd through 1st centuries BCE. But nearly all attempts at dating specific books, with the exception of the Pentateuch (early- to mid-3rd century BCE), are tentative and without consensus.”