What Happened To Our Human Cousins?

The Natural History Museum in London has as many as nine human species which evolved around 300,000 years ago with one of them being Homo Sapiens (us) and probably the best known other being Neanderthals but there was also Denisovans, Homo Longi, Homo Rhodesiensis, Homo Floresiensis, Homo Luzonensis, Homo Heidelbergensis and Homo Naledi so the obvious question is where did the other eight of our human cousins go?
The theories are abrupt climate change, competition and interbreeding between species and each has its merits but one scientist has put it down to Homo Sapiens making an all important invention and it's not the wheel or fire, but the needle.
Homo Sapiens fossil records show that the needle was widely used and was only found in Homo Sapiens fossils and once we had gained the advantage of being able to sew, we were able to make bags, baskets, traps and nets which allowed us to hunt more effectively and stitch tents and clothes which allowed us to stay warm and most importantly, keep our infants warm and increase chances of their survival during the cold ages.
With a greater survival rate, Homo Sapiens quickly became the largest groups and out competed the smaller groups of other humans for resources who were pushed out to the less favourable land and slowly they died out, leaving us as literally the last man standing.   
Other theories are that we interbred with other humans species and there is some evidence of that, as much as 5% of human DNA is Neanderthal so there was certainly some fuzzy bumping going on so maybe we just bonked them out of existence which is probably better than the view i have always held which was that we just murdered them all.  
I base that on looking at what happened to the Natives of other lands we have come across and quickly conquered and murdered them so we probably met and killed our cousins because it is exactly what us Homo Sapiens do.