This seems to me to be similar to the problem of animal species going extinct. We lose something valuable whenever a species or a language disappears from the face of the earth. A people's cultural identity and history is closely tied up with the use of their native language, as a few examples will clearly show.
In "The Story of English", Paul I. Dyck traces the history of the English language and demonstrates how the history of England is inextricably tied up with the preservation of the language. After the Norman invasion and conquest of 1066, French was the language of governance and Latin the language of the church. Dyck asks the question, "how did English survive?"
The answer involves several factors. The common people still spoke their native tongue, and the French invaders took English wives, who taught English, not French, to their kids. Another factor was the gradual loss between 1066 and the mid 1400's of virtually all of the English holdings in France. This led to the development of an English identity, helping to preserve the English language. Another major factor was the structure of English. By this time the grammatical structure had become sound, sound enough that thousands of French words could be incorporated into the English language, as opposed to French replacing the English language.
By the mid-1300's English was clearly taking over. In 1356 the mayor London decreed that future proceedings must be conducted in English, and by 1385 the schools had switched from French to English as the medium of instruction. Then in 1399 Henry IV became the first English King to be crowned in English.
The church, however, still resisted the use of English. In fact, in the early 1500's it was a heresy punishable by death to own an English-language Bible, which was now available thanks to the translation work of William Tyndale. Tyndale himself was located in France and was killed, but about this time Henry VIII broke away from the Catholic Church and henceforth English was permitted in the church.
The next significant event was the battle with the Spanish Armada in 1588. The defeat of the Spaniards allowed English to survive and thrive, but Dyck believes that had the English lost, English as a language would not have survived.
With the publishing of Shakespeare's works, and then the King James Bible in 1611, English had cemented itself as a language which would last, and today it is used around the world.
Let us look at another example, that of the Lithuanian language. As the first of the former Soviet republics to declare its independence, Lithuania has a special interest for me. It seems odd considering its small size today, but in the 14th century Lithuania was the largest country in Europe, containing present-day Belarus, Ukraine, and parts of Poland and Russia. However, during the 18th century its neighbors systematically dismantled Lithuania, cutting it down to its current small size.
According to Richard J. Krickus in his book "Showdown: The Lithuanian Rebellion and the Breakup of the Soviet Empire", the unlikely rise of a nationalistic spirit during the 19th century was due to the common language and the folk culture. Everything argued against the Lithuanian identity: the cities were mostly Polish and Jewish, most of the gentry were Polish or Russian and did not speak Lithuanian, and the clergy was under the influence of the powerful Polish Catholic hierarchy.
Yet, as was the case with the English, the peasants spoke and preserved the language. Krickus writes:
"It was under goading by German philologists that some Lithuanians began to study their mother tongue and their country's history and culture. Later, Russian philologist would become mentors to a new generation of Lithuanians seeking to resurrect their ancient tradition. Foreigners were attracted to the Lithuanian revival by the uniqueness of the Lithuanian language, an ancient tongue that, it was believed, faced extinction. The resurrection of the Lithuanian language among a growing segment of society would have an important influence on the rebirth of Lithuanian nationalism." (p. 7)
The 19th-century Russian Czars tried to limit the use of Lithuanian, and Krickus sums up the situation as follows:
"Throughout history, the Lithuanian language had been both a curse and a blessing to the people speaking it. In denying Lithuanians easy access to intellectual developments elsewhere in Europe, such as political and economic liberalism, it was a curse. Yet, it was a blessing because it sustained a profound sense of national identity and solidarity even in face of German, Polish, and Russian political and economic hegemony.
Along with Latvian, Lithuanian is the last of a line of Indo-European languages that once thrived in the Baltic region. Prussian, a related language, has vanished as a spoken tongue; the last person known to use it died in 1677. Had Lithuanian been cousin to German or Russian, the language and the people speaking it probably would have been absorbed centuries ago." (p. 8)
So the language and the people managed to survive the 19th century, and their spirit of solidarity led to the incredible events of early 1991, when Lithuanians opposed Soviet tanks with their bodies during a tense standoff, which led to 14 deaths but ultimately to the Soviets backing down, giving hope (leading to eventual independence) to the other Soviet republics.
Finally, let's take a brief look at the Tamil language. The Tamil are an ethnic minority in Sri Lanka, who have been oppressed by the Sinhalese majority since the island country gained independence from Great Britain. According to an article in the 3/6/09 Christian Science Monitor, the Tamil rebel group was formed in 1976, and civil war broke out in 1983. Recent reports indicate the government is on the verge of winning this war (if indeed such a war can ever be "won").
What does this mean for the Tamil language? It won't die out worldwide, since it has speakers all around the world. But the importance of language as forging the identity of the Tamil people is shown by this paragraph from a website (obviously written by one for whom English is not a first language):
"Language is one of the most important elements representing the national identity. In Sri Lanka, national language issue seems very influential in both cultural and political sphere; it was the major bone of contention between the Sinhalese and the Tamils. During the 1950s when the nationalism movement was in force, the language question became dominant political issue. By then the Buddhist revivalism also emerged and enforced the adoption of Sinhala as the sole official national language. Eventually, in 1956, despite efforts to conduct the two-language policy, the ruling coalition of the Parliament introduced the Official Language Bill of 1956, making the Sinhala the sole official language. From then onwards, the Tamils who resided elsewhere other than in Jaffna were discriminate against; all public servants were required to have proficiency in the Sinhala language within three years, or they would be penalized and lose their jobs. They were also discriminated against in political, educational and professional opportunity. Language issue led thus to the religio-ethno-nationalism as well as the communal riots in the country."