Temi Samie
There isn't a definitive answer to this question as it depends on how "least common" is defined. However, languages like Njerep, Liki, and Dumi are considered some of the least spoken languages in the world with very few speakers.
Possibly in America. However, it isn't the most common language in the world. Mostly English.
It is difficult to determine the least common language spoken in the world due to limited data and the vast number of languages. However, some of the least spoken languages include endangered indigenous languages with only a few remaining speakers.
It is difficult to know for certain what language the Neolithic people spoke as they did not leave written records. However, linguistic studies suggest that various languages were spoken during the Neolithic period, depending on the region and cultural group.
Mandarin Chinese is the most common language in the world based on the number of native speakers. It is spoken by over a billion people globally.
Mandarin Chinese is the most widely spoken language in the world, with over a billion native speakers.
You speak the same language you spoke at the beginning of World War I.
No one knows what language neolithic peoples spoke, but since they lived in many parts of the world it is reasonable to expect that they spoke many different languages.
They spoke a language that couldn't be translated
Possibly in America. However, it isn't the most common language in the world. Mostly English.
English is an international language, so many people speak it in different countries. So it can be useful to speak it, as more people will understand you than if you spoke a less common language. It is also the international language used for airlines around the world. All pilots speak it.
they valued direct observation
The short answer is 'yes'. Just as mankind before the Tower of Babel had a common language, so there will again be a common language spoken by all men in the future during the Millennium after Jesus Christ returns as King of Kings and Lord of Lords.
English
It is difficult to determine the least common language spoken in the world due to limited data and the vast number of languages. However, some of the least spoken languages include endangered indigenous languages with only a few remaining speakers.
There is no natural language, humans never spoke one international language through the world, however the oldest language known is probably Sumerian because that was one of the first languages to be written
English is the language of all of Australia, however, just about every language in the world is spoken in Melbourne because of the huge immigrant population.
The Romans spoke Latin and they took the language with them as they expanded. At least five major European languages are based on Latin. These languages are known as the Romance languages--Italian, Spanish, Portuguese, French and Romanian. English too, has a strong Latin influence, although is is not actually a "grandchild" of Latin.