Firstly, I would like to address the genetics question - this is often brought up as scientific fact, usually relating to enzymes, but is, in fact, a myth. Rather, there are a number of complex cultural and social reasons for the high levels of alcohol abuse within indigenous populations, and it really comes down to colonialism. Historically, indigenous peoples have been dispossessed of their land and culture, which has lead to high levels of depression, poverty, unemployment, etc. etc. Furthermore, in countries such as the US, Canada and Australia, alcohol was introduced at the same time as settlement occurred, and was seen as a way to ensure the 'docility' of the indigenous populations - particularly in the US when it came to treaty making. Alcohol was also used as a primary method of payment for work, rather than money (this was particularly prominent in the state of Victoria (Australia) during the nineteenth century on cattle and sheep farms). For more information and more general reading, I suggest First Australians (https://www.mup.com.au/items/9780522857535) and http://www.amazon.com/Contemporary-Native-American-Cultural-Communities/dp/0761990593

(Disclaimer: this is my first proper post on AskHistorians, and while I am currently a PhD student in indigenous history, please let me know if my answer could be improved upon - I realise it is a short answer for a complex topic.)

The alcohol problem isn't a myth. Statistics show a higher rate of incidence of alcohol-related deaths within Native American communities compared to the general US population. As well, the extreme range of academic papers on alcoholism amongst Native Americans as well as a general look at history show that alcohol is a problem in reality.

In a very condensed version of events, before colonization, Native Americans didn't know what alcohol was and that worked against them both in trade and vulnerabilities to alcoholism. Proliferation of alcohol also aligned with the desires of colonists to cleanse the land of Native Americans, and so it was very much in the goals of colonialism to allow as much access to alcohol to maximize damage on Native Americans.

Native Americans had no experience with alcohol before their exposure to it by Europeans, as shown by this excerpt from Lamarine's work.

"This population had virtually no history of alcohol use preceding the arrival of Europeans. Having had no experience with alcohol, Native Americans had not developed a social context for its use and were particularly vulnerable to its debilitating effects. The European settlers quickly took advantage of the deleterious effects of alcohol upon Native Americans in order to secure greater advantages in business negotiations."

Colonists also saw alcohol as a method for culling the native population, as shown in this Benjamin Franklin quote:

"If it be the design of Providence to extirpate these savages in order to make room for the cultivators of the earth, it seems not improbable that rum may be the appointed means. It has already annihilated all the tribes who formerly inhabited the seacoast."

This doesn't give insight as to why alcohol remained such a problem after colonization, but I hope this sheds some light on why the alcohol problem began in the first place. Alcohol was seen as a solution to a colonial problem, and the weaknesses inherent among Native Americans stemming from unfamiliarity with alcohol created the perfect storm for alcohol proliferation within Native American communities.

See: "Alcohol Abuse among Native Americans" by Lamarine, Roland J.

"Native Americans and Alcohol: Past, Present, and Future," by Szlemko, William J; Wood, James W; Thurman, Pamela.

"Making the Indian: Colonial Knowledge, Alcohol, and Native Americans" by Quintero, Gilbert

Follow up: Did the same thing happen to other colonized indigenous peoples in other places/eras?