things vary naturally e g the moths some survive better e g the moths the surviver's variation is preserved more than those which survive less because the surviver survives more the net change is toward the better variation it has evolved into the kind with the newer variation it has another different variation less than of the versions of which survive better only some of the new versions propagate the net change is towards the preferred version of this nd variation ditto for a rd variation ditto for a th variation ditto for a th variation ditto for a th variation ditto for a th variation ditto for a th variation ditto for a th variation ditto for a th variation ditto for a th variation ditto for a th variation ditto for a th variation ditto for a th variation ditto for a th variation it is now beyond similarity of the original state repeat for years