>    Regret did not make question clearer. I didn't mean how would early
> humans open nuts.. I meant: how does such an impenetrable seed open in
> nature..*in the absence of humans/animals*..in order to seed the next
> generation of macadamia plants.??
>
> [log in to unmask]

I guess it's like all nuts. If you observe a macadamia nut, there is
something like a "north pole" (where the root grows) and a "meridian".
When the nut sprouts, the nut splits into two parts along the "meridian"

JL