I do believe the ancients never used chicken fat of grease on their leather
They had high quality tallow, goose grease, olive oil, nut oils to choose from
The smell of rancid chicken is too powerful for even their noses
A recent BBC news story (two days ago) that police closed an area of a park whilst forensics checked out a smell. Social Media reported a body had been found. Turned out to be a bag of chicken wings which had been dumped!
Beeswax candles were very uncommon. In the 7th C (600s) a monk wrote to the pope seeking permission to import bees from north France into Ireland (Hibernia) as there were no bees there so he could not make candles
In the 8th to 11th centuries Viking traders imported bees into Hibernia so they could make meade and sell the wax. They recorded that there were no bee hives in Hibernia