Assuming free will exists, why will you be proud/ashamed of something like your dna which is not in your control?

It could've been the lack of public displays of affection. It could also have been things like the repeatedly observed acts including ritual cannibalism and other sorts of mistreatment of prisoners, such as in the Siege of Fort Henry for one famous example. [1] One should not white wash history, but going in the equal but opposite direction is absolutely no better.

Accurately recounting history is also the only way we can learn from it. If you turn a group into mindless evil idiots, then there's little to learn from such. But when you appreciate that there were real issues and awful acts that, in turn, drove no less awful responses from otherwise rationale and intelligent individuals behaving in what they felt was justifiable ways, in a sort of endless pendulum of death and destruction, until there was just one side left standing - it suddenly becomes strikingly similar to modern times in many ways, and there's yet much to learn from it all.

[1] - https://en.wikipedia.org/wiki/Siege_of_Fort_William_Henry

What are the extra proporties you possess?

East Asians apparently have a higher percentage of Neanderthal dna than Europeans, with it going as high as 4%. It's hard to believe that at 2% it's greater than 99% of people, since 2% seems rather average for the average East Asian and the East Asian population being 1.7B or so. East Asians also have Denisovans dna as well.

You make it sounds like he choose to be insecure about it.

It's social conditioning and ego doing it's thing to create pointless suffering/insecurity as usual. Nothing new. It will keep creating suffering for pointless things. The dna % just one of the mere labels it uses.

I wouldn't exactly say anything implies it is rare. 400,000,000 million people possess any particular trait at a greater prevalence than 95% of all people. It's more common than being an American.

I don't mean this as a negative comment aimed at you, but I always hate these sort of anecdote. The joke hinges on something we know to not be explicitly true -- ie, that if someone had more, or less, neanderthal DNA, they would be seen to be less evolved, more crude, etc. The joke relies on a misreading of the consequences for the presence of neanderthal DNA, and is only "funny" if you intentionally misread that yourself, or if you are unaware of the actual facts.