Question

How can our country claim to be the cradle of world's culture

Answer 1

In short: The idea of a nation-state is a modern concept. "Oldest countries" don't exist because what we understand as "countries" are new. There may be some countries perceived as being defined by culture, but these cultural identities are nothing but modern constructions to create a consolidated, unified 'country', either from within the state or from an external perception.

Long: The 28 states of India are extremely distinct. Some Hindus in Kerala eat beef, while some hindus in UP abhor the practice of eating beef. There are 400+ major languages and 4000+ dialects. What we know as "Chinese" food isn't really anything - the food from Sichuan and Manchuria regions are distinct.

The idea of homogeneity is useful to create national fervour and to create a semblance of unique singular national culture - but more often than not, this 'national culture' simply does not exist.

This need to create a identifiable cultural identity based on a past history is extremely important from the nationalist point of view - how else would you have a strong nation, if there is no common bond? But at some point we must realize that these commonalities are nothing but the creation of Imagined Communities or what we do is create certain Invented Traditions to borrow terms from Benedict Anderson and Eric Hobsbawm.

Historically, there never have been singular cultures except within relatively small regions\kingdoms\provinces. Large regions always have had a multiplicity of cultures owing to dynasty, war, trade, religions, languages etc and it would be deluding oneself to suggest that there was a national culture, or spirit of a culture.

Don't get me wrong - there is definitely a kindred spirit I have with my fellow countrymen - although I do not delude myself that this belonging, fraternal feeling, national identity has anything to do with a single indistinguishable culture - i take pride that every community - religious, linguistic, regional has its own unique culture and cannot be singularly consolidated into one big myth of national culture.

Note: This started as a comment thread but thought it could qualify as an answer.