Any given chemical is not equally likely to cause pleasure for human beings, so of course alcohol and nicotine consumption have a genetic basis. It seems equally obvious that the availability of alcohol and nicotine are part of the environment. Additionally, they are parts of the environment where it is easy to imagine life being substantially similar without them (unlike environmental influences such as oxygen and gravity).
Any given chemical is not equally likely to cause pleasure for human beings, so of course alcohol and nicotine consumption have a genetic basis. It seems equally obvious that the availability of alcohol and nicotine are part of the environment. Additionally, they are parts of the environment where it is easy to imagine life being substantially similar without them (unlike environmental influences such as oxygen and gravity).