Its Unconscious Goal: The Production of Humans
He was a firm believer in the chancy-ness of our existence, i.e. there is no really good reason why nature did not stop at fruit flies and ... forget about it.
"Humans are not the end result of predictable evolutionary progress, but rather a fortuitous cosmic afterthought, a tiny little twig on the enormously arborescent bush of life, which if replanted from seed, would almost surely not grow this twig again." - Stephen Jay Gould
Now, you know that I don't share this lowly depiction of man ... or I wouldn't be writing this.
DNA is a neural net
Evolution is the mechanism by which the nature forms inanimate matter into people by throwing various animals at their environment to see if they splatter. It they survive, they get to multiply and pass on their success story.
Who could possibly deny that the brute facts of geometry and physics dictate the position of various body parts? If you can only travel in one direction at once (necessitated by geometry), how is it that the sensory organs would be anywhere else but at the head?
Why do fish swim by swishing their tails from side to side rather than up and down like a whale? Again, geometry intervenes on behalf of the fish ... since the concern of fish is right to left much more than up and down (they live primarily near the surface or the bottom thus interacting with a restrictive plane) ... that's where the action goes. The whale has a different tale to tell. On land, mammals have to move primarily by bouncing up and down. They are in constant contact with the surface unlike fish gliding over or under the bottom or top surface without principle contact. But, clearly either will propel an animal in the water ... so ... it was to no advantage for mammals returning to the water to change their "stroke".
These are the type of primary things that the DNA neural net will pick up on at the earliest stages of evolution and incorporate into the design of a viable biological entity for this particular environment.
In the long run ...
I say that any planet wherein life develops of its own on a gas-solid interface will end up with a two-legged,two-armed, head on top, two eyes forward, crack in the back type humanoid. They may develop differences in appearance in minor ways (perhaps there is a planet of chicken-man where all the above beings are covered in feathers) ... but they will always have major characteristics in common ... because ... these are fixed early on in evolution.
Evolution must proceed till it produces a being capable of turning it off. The details of how it proceeds are not entirely random either.
Branching and pruning
DNA represents a growing tree of life. Think about it "The Tree of Life" (not the "Circle of Life" ... that has to do with the "action" of the thing rather than the thing itself).
The trunk of the tree is represented by the most basic attributes of living things:
How could it be otherwise?
At the earliest stages ...
Progress was very slow. Not knowing any fundamentals, the neural net was cast about at random just as Gould envisioned. The earliest trials were vastly different than anything we see today because those fundamental differences were not yet ruled on by the death struggle. Where does the head go? How many legs are needed? How to move on a surface? As bad designs were scrapped, the better ones were incorporated into the trunk DNA so that current animals have a "familiar" quality about them born of their common attributes. We simply don't see fundamentally different animals anymore. They've been pruned out long ago and will never come this way again. They can't develop again because the trunk data is never changed anymore ... it would simply result in an abortion when loaded up with all the other information. A broken or misshapen limb won't support the weight that the other had been designed for.
And experimentation virtually stops when another animal is in the way, i.e. already developed. To keep fundamental experimentation going we would need a wipe out of all major life forms ... todo ... nothing left but single celled animals. Then, nature would have to do it over again and sooner or later would end up cookin' up another two legged creature like us.
When the fundamentals were fixed, progress into every niche was very rapid by comparison. And if ever there is a near wipe out, rapid progress to fill the niches will again be warranted. When the niches are already filled there can be no quick progress because of competition ... and ... evolution slows down considerably. When the available niches are saturated evolution just about comes to a halt. We then have only variation on the same theme adapting to small changes in the environment or in the animals themselves. It would never stop completely because the environment is not completely stable.
How anyone could form the view that we are random and not inevitable (given the present information available), is unfathomable to me.
DNA looks like identical strings.
It doesn't have the shape of a tree. The most fundamental information looks just like the most trivial. Judging only by appearances, we would have to say that it's all random because the hierarchical structure is not readily apparent. Perhaps in the future it will be found that such fundamental data is redundantly iterated in DNA so that the more times a statement is made, the more stable it is. I won't hold my breath though.