"We had light and dark moths before the industrial revolution ,"
"Actually , we did n't . The first record of a melanic form was in 1848 . Presumably other melanic individuals had appeared before this , both in Biston bebularia as well as other moths . We know that a similar mutation occucrred in other moths North America some years after the 1848 record of the B. betualria . There are actually several alleles of the gene responsible for color that form a dominence hierarchy with the fully black morph ( called carbonaria ) as the top dominant and the typical as recessive . The intermediate forms are referred to as insularia . They are uncommon . At any rate , by 1895 , 98 % of observed B. betularia in industrialized areas were carbonaria ."
"light and dark moths before the industrial revolution"
"the top dominant and the typical as recessive"