This is my attempt to create the smallest, most concise anti-birth gene possible.
cond
*.robage 2 <
start
.tie *.robage 1 add mult inc
.deltie inc
stop
You can even get rid of the condition if you aren't going to be using ties with ID of 1.
cond
start
.tie *.robage 1 add mult inc
.deltie inc
stop
And if you don't mind losing a cycle:
cond
start
.tie *.robage mult inc
.deltie inc
stop
Now that's tiny!