It appears that there is no definitive answer. Here's some speculation from Wiki:
Identifications and depictions
The word
fruit appears in Hebrew as פֶּ֫רִי (
pərî ). As to which fruit may have been the forbidden fruit of the
Garden of Eden, possibilities include apple, grape, pomegranate,
fig,
carob,
etrog or
citron,
pear, quince, and
mushrooms. The
pseudepigraphic Book of Enoch describes the tree of knowledge: "It was like a species of the
Tamarind tree, bearing fruit which resembled
grapes extremely fine; and its fragrance extended to a considerable distance. I exclaimed, How beautiful is this tree, and how delightful is its appearance!" (
1 Enoch 31:4).
In Islamic tradition, the fruit is commonly either identified with wheat or with grapevine.
Apple
In
Western Europe, the fruit was often depicted as an
apple. This was possibly because of a misunderstanding of – or a pun on – two unrelated words
mălum, a native
Latin noun which means evil (from the adjective
malus), and
mālum, another Latin noun, borrowed from Greek μῆλον, which means apple. In the
Vulgate,
Genesis 2:17 describes the tree as
de ligno autem scientiae boni et mali : "but of the tree [literally
wood ] of knowledge of good and evil" (
mali here is the
genitive of
malum). The
larynx, specifically the
laryngeal prominence that joins the
thyroid cartilage, in the
human throat is noticeably more prominent in
males and was consequently called an
Adam's apple, from a notion that it was caused by the forbidden fruit getting stuck in Adam's throat as he swallowed it.
Grape
Rabbi Meir says that the fruit was a grape, made into wine. The
Zohar explains similarly that
Noah attempted (but failed) to rectify the sin of Adam by using grape wine for holy purposes. The midrash of Berei**** Rabah states that the fruit was grape, or squeezed grapes (perhaps alluding to wine). Chapter 4 of 3 Baruch, also known as the Greek Apocalypse of Baruch, designates the fruit as the grape. 3 Baruch is a first to third century text that is either Christian or Jewish with Christian interpolations.
Fig
The Bible states in the book of Genesis that Adam and Eve had made their own fig leaf clothing: "And the eyes of them both were opened, and they knew that they were naked; and they sewed fig-leaves together, and made themselves girdles". Rabbi
Nehemiah Hayyun supports the idea that the fruit was a
fig, as it was from fig leaves that God made garments for Adam and Eve upon expelling them from the Garden. "By that with which they were made low were they rectified." Since the fig is a long-standing symbol of female sexuality, it enjoyed a run as a favorite understudy to the apple as the forbidden fruit during the
Italian Renaissance,
Michelangelo Buonarroti depicting it as such in his masterpiece fresco on the
Sistine Chapel ceiling.
Pomegranate
Proponents of the theory that the Garden of Eden was located somewhere in what is now known as the Middle East suggest that the fruit was actually a
pomegranate, a plant indigenous from Iran to the Himalayas and cultivated since ancient times. The association of the pomegranate with knowledge of the underworld as provided in the Ancient Greek legend of Persephone may also have given rise to an association with knowledge of the otherworld, tying-in with knowledge that is forbidden to mortals. Also, it is believed Hades offered Persephone a pomegranate to force her to stay with him in the underworld. Hades is the Greek god of death and the Bible states that whoever eats the forbidden fruit shall die.
Wheat
Rabbi Yehuda proposes that the fruit was
wheat, because "a baby does not know to call its mother and father until it tastes the taste of grain."bIn Hebrew, wheat is "khitah", which has been considered to be a
pun on "khet", meaning "sin" Although commonly confused with a seed, in the study of
botany a
wheat berry is technically a simple fruit known as a
caryopsis, which has the same structure as an apple. Just as an apple is a fleshy fruit that contains seeds, a grain is a dry fruit that absorbs water and contains a seed. The confusion comes from the fact that the fruit of a grass happens to have a form similar to some seeds.
Mushroom
A fresco in the 13th-century
Plaincourault Abbey in France depicts Adam and Eve in the Garden of Eden, flanking a Tree of Knowledge that has the appearance of a gigantic
Amanita muscaria, a
psychoactive mushroom.
Terence McKenna proposed that the forbidden fruit was a reference to
psychotropic plants and
fungi, specifically
psilocybin mushrooms, which he theorized played a central role in the
evolution of the human brain. Earlier, in a well-documented but heavily criticized study,
John M. Allegro proposed the mushroom as the forbidden fruit.
Banana
Several proponents of the theory exist dating from the thirteenth century. In Nathan HaMe’ati's 13th century translation of
Maimonides's work
The Medical Aphorisms of Moses, the
banana is called the "apple of eden". In the sixteenth century,
Menahem Lonzano considered it common knowledge in
Syria and
Egypt that the banana was the apple of Eden.
