Here is a simple, Jain-sourced view of “proof” for Jain history:

• Jainism is believed to be an eternal dharma (anādi-ananta), not something that began at a single point in history. The tradition holds that the teachings have always existed and are revived in each time cycle by the Tirthankaras. In the current cycle, Mahavira is the last Tirthankara who helped organize and spread the faith in its current form. You can read more on this perspective here.

• The historical timeline within Jainism does have traditional dates that vary between Digambara and Śvetāmbara sources. For example, Mahavira is often placed around 599–527 BCE (Śvetāmbara) or 540–468 BCE (Digambara), with Parshvanath earlier still. Such dating differences are common in Jain scholarship, but both traditions agree on the core sequence of Tirthankaras and the transmission of Jain teachings across ages. You can read a concise overview of these discussions here.

• For a sense of the kinds of archaeological and inscription-based evidence that people cite in support of Jain antiquity (beyond purely doctrinal claims), see discussions that summarize early Jain inscriptions and material remains, along with how traditional dates are reconciled with archaeological finds. You can read a Jain-focused summary here.

If you’d like a very targeted Jain-perspective article or a specific tradition (Digambara vs. Śvetāmbara) explained, I can point to a more precise JainKnowledge page on that topic.