So most of my interest in haplogroups came from recorded history, the Slavs etc.

Lately I've been reading into its further origins. According to Eupedia, I2 was the most common haplogroup in Europe up to the end of the Mesolithic? Is this true? I've seen a few sites saying otherwise or mixed things.

What other haplogroups were common in Europe at the time and by how much was I2 more common? I mean, if we even have the answers.

I read it was gradually replaced by G then the R1a/b haplogroups. Was this due to warfare or disease or that the new arrivals were farmers?

Do we know which tribes/cultures may have been dominant with haplogroups I? What did these hunter gatherers leave behind? Did they build stone henge? Were there no haplogroup R lines in Europe at all? And what were they
(R people) doing at this time?

Also, do we know if these ancient Europeans influenced today's languages at all?

Not sure if this is the right page to ask these questions.