Verification of the family tree of the Makino family of the Nagaoka domain by DNA analysis

During the Edo period in Japan, the Makino family served for generations as the feudal lords of the Nagaoka domain, which ruled the northern part of the Chuetsu region and the western part of the Kaetsu region in present-day Niigata Prefecture. Two different family histories have been handed down regarding Makino Tadahiro, the 8th lord of the Nagaoka domain. According to official records, Tadahiro was from the Kasama Makino family (relatives of the Nagaoka Makino family). However, an unofficial record of the Nagaoka Makino family states that Tadahiro was the biological son of the 5th lord of Nagaoka, Makino Tadachika. Why two different records were passed down to posterity together, and which of these records is correct, are extremely interesting historical mysteries. To verify which of these records is correct, we conducted a kinship study by the autosomal and Y-chro‍mosome short tandem repeat analysis of three individuals: Tadahiro, Tadachika, and the 4th lord of Nagaoka, Tadanaga (the biological father of Tadachika). The results showed it was highly probable that these three individuals have a grandfather–father–son relationship. This is the first report to use DNA analysis to prove which of several family trees of the feudal lords of the Nagaoka domain is correct.