Genealogists often lament the fact that immigrant ancestors did not pass on their native languages to their descendants.While the children of immigrants were mostly fluent in those languages - the first generation - those children only rarely passed down those languages to their own children or grandchildren - thus losing them forever.
Years ago, as I sat struggling through Cyrillic to understand records from Mogilev, Belarus, I often wished my great-grandparents had passed down Russian and Yiddish. Russian seems to have disappeared the day the family hit the streets of New York, while Yiddish was transmitted to their children. Their grandchildren knew only phrases or could understand some but not speak it, and they only rarely could read it.
How much easier it would have been if I had learned both languages fluently from my parents and grandparents! However, I did learn Farsi fluently when we lived in Iran. Our daughter studied it, used to read and write it, understands it nearly fluently, but refuses to speak it.
Now, through one scientist's research, we learn that there are two major reasons that people should pass their heritage language on to their children.