What he's saying is, while a moth appears to be one animal, with a wormy start and a flying finish, it's actually two animals — two in one! We start with a baby caterpillar that lives a full life and then dies, dissolves. There's a pause. Then a new animal, the moth, springs to life, from the same cells, reincarnated.
According to this theory, long, long ago, two very different animals, one destined to be wormy, the other destined to take wing, accidently mated, and somehow their genes learned to live side-by-side in their descendants. But their genes never really integrated. They are sharing a DNA molecule like two folks sharing a car, except half way through the trip, one driver dissolves and up pops his totally different successor.
Many insects begin life as worm-shaped, leggy, tubular thingies that spend lots of time eating. We call them grubs or maggots or caterpillars, and they are programmed by a set of genes that sit in their DNA, spelled out in chemical letters, A, C, T and G.Notice I've put my "caterpillar" instruction genes on the left side of the DNA. The instructions on the right side are, temporarily, silent.
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