Evidence for Westward Indo-Aryan expansion:

The primordial Rig Vedic river goddess Danu  is the mother/progenitor of the Danava clan  of Indo-Aryans. The Danavas revolted against the Devas, and were eventually defeated and banished. As it turns out, that was far from the end of their story.

The word dānu means “fluid, drop” in Rig Vedic Sanskrit. The Avestan (old Iranian) word for “river” is “dānu”. The Scythian (Saka/Shaka) & Sarmatian words for “river” are also “dānu”.

Now consider this: linguistically, the names of the European rivers Danube, Dnieper, Dniestr, Don, Donets, Dunajec, Dvina/Daugava, and Dysna are all derived from the Rig Vedic Sanskrit root word “dānu”. These rivers flow across eastern & central Europe. These rivers, all named after the Rig Vedic goddess Danu, seem to trace the gradual westward migration through Europe of the Danava clan of Rig Vedic Indo-Aryans.

So where did the Danavas eventually end up?

According to Irish & Celtic mythology, the Irish & Celtic people are descended from a mother goddess – a river goddess – called Danu. The ancient (mythological) people of Ireland are called the Tuatha Dé Danann (Old Irish: “The peoples of the goddess Danu”).

Is there genetic evidence to support this story? As it turns out, there is. The R1a1a haplogroup is rare in Ireland, at 2.5% of the population. This can be explained by the fact that Ireland has suffered many invasions since the Bronze Age, which would have led to the gradual replacement of the R1a1a haplogroup with those of the various invaders. The fact that R1a1a is still present in Ireland proves that people of Indo-Aryan origin settled there in the past.