Why not include North and South Americans and the South Pacific in this same comparison, because they all fell victim to European colonization...
There are many reasons.... Why did one group of people develop faster than the other? It had to do with Geographic Advantages enjoyed by Eurasia, and all the waterfall of advantages which came with those geographic Advantages.
The landmass of Eurasia, laid out on an east-west axis, allowed for the sharing of crops, animals, germs(diseases) and ideas. The Americas and Africa, stretched out on a north-south axis, traverse various climate zones and geographic boundaries which discourage trade.
Major portions of Eurasia had a natural advantage in developing agriculture in the presence of plants that could be easily domesticated. Domesticated Animals here was also an advantage.
North and South America, as well as Africa had a lack of large domestic animals such as Europe and Asia.. ( Europe had the Horse, Oxen). Asia had these and the Elephant. (*) African elephants are not domesticatable, nor is the Zebra, nor is the water buffalo; The America's have the horse, but the horse is not native to the continent it was brought by early European settlers. Farming and domesticating animals provided social stability that is lacking in in hunter gather societies. Living so proximal with large domesticated animals was also an advantage in developing and immune system to a larger variety of germs, that even sophisticated American, South Pacific, and African cultures did not benefit from. Also Labor specializations naturally falls out of living with domesticated animals, this enabled certain groups of labor to eventually develop weapons.
All of these advantages along with the diversity and density of Eurasian populations created an immunity to germs that would later decimate the more isolated populations of Africa and the Americas, when the two populations ultimately did come into contact. This allowed Europeans easy conquest of decimated indigiouns people again and again and again when they came in contact with them.
When or if the population developed Gun Powder and Steel also falls out of the above advantages and plays a role. A lesser role however because it must be tied to either diversity of government or a government willing to pursue the technologies.. China developed gunpowder first but did not benefit from it; and Japan developed superior steel and fire arms first but because of their feudalistic prejudice against guns and a fascination with the sword; failed to capitalize on either advancement.
All these Ideas are tied together and better explained in Jared Diamond NYTimes best selling book, "Guns, Germs and Steel".
Alternatives Theories to Guns Germs and Steel..
Crosby's 'Ecological Imperialism: The Biological Expansion of Europe
900-1900'. Book came out about a decade before Diamond's, written more for scholastic consumption, wildly popular across many disciplines (medical, historical), comes to some of the same conclusions about weapons and germs, but not as comprehensive. Still a good read.
Works by philosophers R.G. Collingwood, Ludwig von Mises, and Michael
Oakeshott. All Philosophers who attempt to explain human past by reference to general laws or broad patterns, which itself is controversial in some circles.
Hitler's "Mein Kampf" and "Zweites Buch", It all goes back to India and the Himalayas, and a few young folks who couldn't keep their pants on.