When the hands become a currency, they are harvested by all means.

Some native Africans were employed to act as the enforcement of this colonial rule. And I don't say that to shift blame onto those Africans, it was a terrible dilemma; do you A) want to break your back trying to make impossible quotas for rubber and see your children lose their hands when you fail, or do you B) want better pay and protection for your family by being the one doing the cutting? Unless you can be sure that nobody else will accept B and thus make such harsh colonial rule unenforceable, it is safer if you accept B. The manual labour of genocides is often carried out by members of the group that is being subjected to genocide; Cremations and burials in the camps of the Holocaust was usually done by camp prisoners themselves.