I would kill. 2X growth rate is too fast, and it is easily better 100 random people now than 200 immediately after.

What about these rules?

• The group of people in the tracks is randomized every time.

• The group always includes the person that the current decision maker loves the most.

• The choice is to kill, or to increase the number of people in the kill group by one.

• If the number of humans available reaches the population number, everyone dies.

• The list of every decision made by every decision maker is public knowledge.

• You are the first decision maker.