Zoroaster (Dating)

Modern linguistic evidence does not support a 6th Century date for Zoroaster, but most mainstream academics accept that date today.
The Avestan hymns, prayers, and scriptures – and the Avestan language by extension – was on of the earliest topics studied in comparative linguistics. Even the earliest 18th century linguists noticed the close relationship between Sanskrit and Avestan, which formed the initial basis for the idea of an “Aryan” language group, which we now call Indo-European, named for how both languages used “Aryan” to describe the in-group of the authors.

Linguistic study has come a long way since that initial connection. There are now established, predictable patterns of change that can be used to date how much time passed between stages of a language, diversion from a parent language, how written vs oral traditions effect a language, and even how to date a languages influence on another language. Much of this is part of the field of quantitative linguistics. Using these patterns, it becomes clear that the Iranian languages split from the Indo-Aryan language that produced Sanskrit no later than 1500 BCE, and the Eastern and Western Iranian languages split apart not long after that. From there, comparisons to later Eastern Iranian languages like Sogdian or Bactrian, and it’s influence on Western Iranian languages like Old and Middle Persian help date Avestan.
Avestan itself was easily identified as two distinct phases or languages depending on how you want to think of it. It can be loosely compared to Middle vs Modern English. These two phases are called Old Avestan and Younger Avestan. The latter makes up most of the Avesta and linguists have identified different phases within that corpus. Comparison with other languages and predictable changes put Younger Avestan as a spoken language between 900-400 BCE. Old Avestan is thus the much smaller corpus that predates 900. In order of age, it includes the Gathas, Yasna Haptanghaiti, and the “Five Sacred Prayers.” The prayers are just a few lines each, and contain the early elements of Younger Avestan grammar. The Yasna Haptanghaiti is also fairly short and appears to be a slightly younger variant of Old Avestan than the Gathas, possibly incorporating an even older verse in the middle.

The Gathas are thus the oldest section of the entire Avesta, dated to around 1500-1000 BCE. Given the apparently rapid shift from the Old Avestan of the Gathas to the Younger elements of the Yasna Haptanghaiti, more and more authors are leaning into the latter half of that range. Not coincidentally, they are also the section of the Avesta traditionally attributed to Zoroaster himself. I’m going to answer the second question first, since we’re on the topic here. The Gathas are very consistent in terms of style and content, so much so that they are generally believed to be the product of one author, or at least a very organized small group. They also portray the speaker as calling himself Zoroaster in multiple instances. That’s about as close as you can get to identifying a specific author for a Bronze Age oral tradition.
That is the information and the process used by most modern scholars to assert a c.1000 BCE date for Zoroaster:
The Classical Greek sources, like Aristotle, and later Roman authors who cited them, largely agreed that Zoroaster was considered impossibly ancient, with a tradition popping up in Greece that placed him 5-6000 years before their own time. The Sassanid Middle Persian sources don’t shed much light on the situation, but the 4th Century Roman historian, Ammianus Marcellinus does. While describing northeastern Iran he wrote:

In these parts are the fertile lands of the Magi, about whose sects and pursuits — since we have chanced on this point — it will be in place to give a few words of explanation. According to Plato, the most eminent author of lofty ideas, magic, under the mystic name of hagistia, is the purest worship of the gods. To the science of this, derived from the secret lore of the Chaldaeans, in ages long past the Bactrian Zoroaster made many contributions, and after him the wise king Hystaspes, the father of Darius. (XXIII.32)
https://www.cambridge.org/core/journals/bulletin-of-the-school-of-oriental-and-african-studies/article/greek-origin-of-the-sixthcentury-dating-of-zoroaster/74CFA27F353B68AB66EAF79F56379DB1

Zoroaster is said to have lived in the sixth century B.C. This has been a tradition, within Zoroastrianism itself, for around two thousand years. Up until recently in the West its accuracy was widely considered an established fact. Western scholars came across the evidence for this tradition in the nineteenth century. Many immediately gave it a warm reception. After all, such a late dating was far better suited to the forward-looking, evolutionary spirit of the times than the much earlier one that had been favoured up until then, but which risked losing sight of Zoroaster in a suspiciously distant past. Also, as well as sounding eminently reasonable it seemed to have the pedigree of a genuine Zoroastrian tradition.

Allusions placing Zoroaster at 6000 B.C:

• Pliny the Elder (23-79 CE)
• Plutarch (1st century CE)
• The Scholion to the Platonic Alcibiades

Allusions associating Zoroaster’s Name with Semiramis and Ninus:

Native Tradition as to Zoroaster’s Date:

Estimates for the lifetime of Zoroaster vary widely, depending upon the sources used:

• 1400 B.C. to 1000 B.C., which represents the current scholarly consensus, is cited by Mary Boyce in her A History of Zoroastrianism ( 1989).
• “Before 458 B.C.” is cited by H.S. Nyberg in Die Religionen des Alten Iran ( 1938).
• The Bundahišn or Creation, an important Zoroastrian religious text, cites the time of Zoroaster as 258 years before Alexander the Great’s invasion of Persia (i.e., 588 B.C.). This “Traditional Date of Zoroaster” was accepted by many 19th century scholars, among them Taghizadeh and W. B. Henning.

• Other scholars such as Darmesteter placed Zoroaster around 100 B.C, argued for later dates.

Linguistic evidence:
From an early time, scholars such as Bartholomea and Christensen noted problems with the “Traditional Date;” namely in the linguistic difficulties that it presents. Tradition holds that Zoroaster composed the eighteen poems that make up the oldest parts of the Avesta, the Gāthās. The language of the Gāthās and the text known as Yasna Haptanghaiti (the “Seven Chapter Sermon”) is called Old Avestan, and is significantly more archaic than the language of the later parts of the Avesta, Young Avestan. Gathic Avestan was still etymologically similar to the Vedic Sanskrit of the Rigveda. Sound changes separating the two branches, which both descended independently from Proto-Indo-Iranian, include the loss of z, the development of a retroflex series in Indo-Aryan, and loss of aspiration and of prevocalic s in Iranian.

Since Rigvedic Sanskrit is slightly more conservative than Gathic Avestan, the Avesta is usually dated to a few centuries after the Rigveda. Based on the date of the Rigveda’s composition, commonly stated as between the 15th and 12th centuries B.C., and a date of Proto-Indo-Iranian of roughly 2000 B.C., the Gāthās are commonly dated within two hundred years of 1000 B.C.
Historical evidence:
The historical approach compares social customs described in the Gāthās to what is known of the time and region from other historical studies. Since the Gāthās are cryptic and open to interpretation, this method also yields only rough estimates. The Gāthās seem to indicate a society of nomadic pastoralists, which contrasts sharply with the view of Zoroaster living in the court of an Achaemenid satrap such as Vištaspa. The absence in the Gāthās of any mention of Achaemenids or any West Iranian tribes such as Medes, Persians, or even Parthians, makes it unlikely that the historical Zoroaster ever lived in the court of a 6th century satrap. Though it is possible Zoroaster lived sometime between the 13th and 11th centuries B.C., before Iranian tribes settled in the central and western areas of the Iranian Plateau, it is just as likely for him to have lived in a rural society during the centuries immediately after the Iranian migration. Therefore, though the historical estimate is consistent with the linguistic one, it is just as vague; Gherardo Gnoli gives a date near 1000 B.C.
Archaeological evidence:
Archaeological evidence is usually inconclusive regarding questions of religion. However, a Russian archaeologist, Viktor Sarianidi, links Zoroaster to circa 2000 B.C. based upon excavations of the BMAC (Asgarov, 1984).

Indo-Iranian religion is generally accepted to have begun in the late 3rd millennium B.C. (e.g., the Soma cult), but Zoroaster himself already looked back on a long religious tradition. The Yaz culture (circa 1500-1100 B.C.) in the Afghan-Turkmen-Iranian border area is considered a likely staging ground for the development of East Iranian and early Zoroastrian practices.
Mythological evidence:
Zoroaster was famous in classical antiquity as the founder of the religion of the Magi. His name is mentioned by Xanthus, Plutarch, Pliny the Elder, Diogenes Laertius, and by Plato in the Alcibiades. Ancient Greek estimates are dependent upon Persian mythology, and give dates as early as the 7th millennium B.C., which are the dates to which Parsis subscribe.
Persian mythology, primarily the Shahnama of Ferdowsi, and oral tradition place Zoroaster quite early. Manly Palmer Hall, in his book Twelve World Teachers, arrives at a rough estimate ranging from 10000 B.C. to 1000 B.C..

1. Another article on dating:
2. ]https://www.jstor.org/stable/607086