Minimum wage proponents say higher minimum wages won't cause unemployment. The first fundamental law of demand, to which there are no exceptions, says when prices rise people tend to buy less and when they fall people tend to buy more. When beef prices rise we buy less. When interest rates rise we take out fewer mortgages. After all if people didn't respond that way sellers could charge any price they wanted and we'd still buy it.
Labor services are no different.
Among those substitutes are automation, moving to a lower wage country and customer self-service. Low wages are more a result of people being under productive rather than underpaid. They simply do not have the skills to produce and do things their fellow man highly values. Seldom do we find poor highly productive individuals or nations. Those who earn low wages tend to have low skills and education.