speciation has definitely occurred when two groups of related organisms
a) cannot interbreed successfully.
b) have drastically different behaviors.
c) have drastically different appearances.
d) become permanently isolated from each other.

Humans have survived and thrived in mexico city by using technology to create greater access to land. when the spanish conquered the aztec capital, tenochtitlan, in the 16th century, they built mexico city by draining the lakes and filling in the lake water to create more arable land for agriculture. this technique of land reclamation has continued to be fundamental to human civilization in mexico city. 

Anstobacco uses;  

Largely uneconomic because they provide little profit or food surplusi think so