Wherever the Hittites and their Anatolian relations are discussed, the claim that they were Indo-European peoples is always stated quite matter-of-factly. This claim is based exclusively on the fact that the Anatolian languages had some vocabulary and grammatical forms which were evidently related to Proto-Indo-European in some way. But apart from this apparent Indo-European component of the Anatolian language group, there is nothing at all to indicate that the Anatolian peoples were in fact Indo-Europeans.
It is interesting that there are hardly any documents to be found on the Internet that discuss the obviously non-Indo-European aspects of the Anatolian languages, including clearly non-Indo-European vocabulary. So far, all that I have found on this is an article called “Possible Non-Indo-European Elements in Hittite” by J. Dyneley Prince that dates from 1921: https://www.jstor.org/stable/593722?seq=1#metadata_info_tab_contents . But of course, there are a number of researchers diligently trying to produce Indo-European etymologies for Hittite vocabulary.
One of the more intriguing features of the Hittite language is its relatively uncomplicated verb compared to the reconstructed Proto-Indo-European verb – among other things, the Hittite language lacks any subjunctive or optative forms. This is usually explained by saying that the Anatolian languages lost much of the Proto-Indo-European forms that their (supposedly) Indo-European ancestors had used. I think it much more likely that it was due to the ancestors of the Anatolians borrowing only the forms of the Proto-Indo-European verb that corresponded with their original non-Indo-European verb forms.
Just looking at the proper names of the Hittites and their gods gives one the clear impression that there is a blatantly non-Indo-European nature to them. It would be interesting to see Indo-European etymologies for proper names like Suppiluliuma or Telipinu (cf. Hattic pinu ‘child’), but I’m not holding my breath on that. I think it rather odd that an Indo-European people would have a total dearth of Indo-European names – especially their kings. Indeed, the names of the Hittite kings have more than a passing resemblance to the names of the Gutian Kings that appear on the Sumerian King List (compare Hittite Suppiluliuma and Gutian Elulumesh, or Hittite Arnuwanda and Gutian Yarlaganda), and I don’t mind suggesting that the ancestors of the Anatolian peoples and the Gutians were possibly related.
Aside from language, genetic analysis of the Hittites and other Anatolians would be very nice to see. But for some odd reason, it seems that looking at the genetics of the Hittites isn’t a high priority for genetic researchers. There simply isn’t any information at all on Hittite genetics as far as I can tell. By now, most Wikipedia articles on ancient peoples and cultures have a subsection on genetics, but there is no genetics subsection for the Hittites…
Of course, if the Hittites really were Indo-Europeans, the prevalent Y-DNA haplogroup among them would have to be R1b (or perhaps R1a, although that would be unlikely given that the distribution of R1a folks was more northerly than that of R1b folks). It’s probably safe to assume that the prevalent Y-DNA haplogroup among the Anatolian peoples was something quite other than R1b; my guess is that it was probably some clade of Y-DNA haplogroup G, a haplogroup which is quite common among the folks of the Caucasus region, and well-represented in Turkey as well as northwestern Iran.
Another thing that could help in more securely categorizing the Hittites as Indo-Europeans would be clear links between their culture and the culture of known Indo-European groups. I haven’t seen much about this apart from the apparent connection between the Hittite god Illuyanka and the Proto-Indo-European “Dragon Slayer” myth (a connection featured in Calvert Watkins “How to Kill a Dragon”). But it should be mentioned that the “Dragon Slayer” myth is not unique to the Indo-European peoples. And even if the “Dragon Slayer” myth among the Hittites was of Indo-European origin, it could easily be a result of borrowing (as was also the case with the Indo-European elements of the Hittite language).
Even though the Hittite language and other Anatolian languages did undoubtedly have an important Indo-European component, I frankly don’t believe that the Hittites and other Anatolian peoples were Indo-Europeans, and I have yet to see anything to make me believe otherwise. At most, I would admit only that the Hittites and other Anatolian peoples were somewhat “Indo-Europeanized”. In my post called “The Movements and Expansions of Indo-European Language Groups” (https://vellaunos.ca/2021/03/24/the-movements-and-expansions-of-indo-european-language-groups/), I suggested that the Anatolian language group “is the result of the (partial) adoption of South Indo-European by the non-Indo-European speakers north of the Caucasus who had produced the Maykop Culture”. But I now think it more likely that it was the Novotitorovka culture instead of the Maykop culture in which the Anatolian language group developed in contact with the South Indo-Europeans (or Steppe Indo-Europeans) of the Yamnaya culture.