DNA is a series of approximations that had to diversify for six hundred MILLION years after the advent of reproduction that involved exchanging DNA (sex) to reach homo sapiens. DNA researchers, if pressed, are likely to admit that the tightly woven series of WowThatWorkedOutAndIDidn’tSeeItComing moments that constitute our three billion codons looks like a collision in a parts bin more than a Detroit Diesel Design output.
Why is that? Precisely because an incredible series of very small copying mistakes, or cosmic ray level disruptions, is constantly at play. Not one of these changes has been “by design.” Rather, the effect on reproductive success reveals which changes were “accidental” and which were “serendipity.”
Here is one isolated datum to illustrate the larger point: dog breeders have failed to make puppy-like long-nosed breeds, and failed to make non-puppy-like short nosed breeds. It’s the other way around, i.e. breeding for hunting skills has involved allowing development to proceed to full functionality (like the long, turbinated adult nose that helps a dog smell) while breeding for lap dog cuteness has only worked when the successive generations fail, more and more, to develop those adult traits. Like long noses.
Why is that? It turns out that the DNA doesn’t have separate coding for “I’m playful and cute” and “I have a superb smeller.” Instead, traits bind together because development from puppy to adult is a continuum, and you can’t get off the continuum early without giving up things that develop later. And why is that? “It’s complicated,” which is exactly the point. It’s messy.
Individual genes turn out to have multiple good effects, as though each one is capable of “Swiss Army Knife” utility, in some limited way. Genes interact in ways that only unfold when, at some point, their combination is A) beneficial and B) gets coded into some of the controlware in the genome.
There aren’t just genes in the genome – far from it. For instance there is a “homeobox” which tells insects to have six limbs, arachnids eight and chordates four. Mess with that, and you will run across a way to make a fruit fly with four legs not six. GOD help us if some loose cannon in a DNA lab wants a child with four arms, because that isn’t actually too far out of reach.
All of the wonder and glory of every different genome coalesced via an enormous series of accidents. Once in a while a “good accident” turned out to be a “These dice are GENIUS” grade accident. When enough good accidents accrue, you might get fins on fish, rudimentary eyes, nerve clusters that develop into brains, better eyes, a swim bladder that helps a fish float, and finally that existential O CRAP!!! moment when some poor fish’s swim bladder and its throat weren’t divided from each other.
That was a rough go for a while, but in time that species used its swim bladder to breathe air, and its stumpy fins to propel itself across the beach mud. Invent your own series of little accidents that could have made the inside of the bladder able to do what gills do, i.e. take oxygen into the blood. The genes for that were already on hand . . .
There WAS NO stage of development along the way from light-sensitive cells to the eagle’s astounding eye that was not gradual and did not involve some series of “good” accidents, including of course a few “These dice are GENIUS” changes. Looking at the complexity that is there and assuming that “There is NO WAY that could have come together by chance,” is to say that your brain is powerful enough to prove a negative.
The real intelligence in the design began with particle physics. Minute changes to the particle physics we understand today, i.e. jigger any of a fairly good-sized number of “arbitrary constants” that define — the strengths and properties of the four nuclear forces; the speed of light; the relative weights of subatomic particles; the placements of electron orbits around an atomic nucleus; the sizes of the quanta themselves that control all of the above — and stars might not form. Or if they did, they wouldn’t cook hydrogen and helium into the heavier elements. Or if they did that, those elements wouldn’t work as elegantly as they actually do. OR if they worked kinda like they do, DNA wouldn’t work as elegantly as GOD had in mind when HE said, “LET THERE BE LIGHT.”