The Direction of Evolution

The recent death of Stephen Gould brings to mind on the matters of evolution he was staunch advocate of, that evolution is completley random. However, there are some that believe that evolution, has a goal it is trying to obtain.

The author of this article is a member of the later group.

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.

Link

What do you think?

An excellent alternative look at this concept of "directional evolution" was in Wayne Barlowe's amazing book of art, "Expedition". It's a phenomenal combination of speculative fiction, biology, and art. WayneBarlowe.com

It was recently turned into a Discover Channel Special: Alien Planet

It examines possible extraterrestrial biology and evolution as a result of a very different environment than earth.

BlackJackal

This so interesting . . . I knew something was different about whales and fish but I never realized until your made this thread that it was because they move their tail different.

Occurs I know one is a mammal and the other one a fish. Even at my age you learn something new each day.

But how about dolphins?

Originally posted by BlackJackal
Why do fish swim by swishing their tails from side to side rather than up and down like a whale?

Because of evolution, not because of geometric constraints.

These are the type of primary things that the DNA neural net

There is no 'DNA neural net'. THe author seems to be ascribing sentience to 'natural selection' itself.

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

This is purely speculation, that natural wants to make humans, and does so by attempting lots of different forms agianst the environment.

but they will always have major characteristics in common ... because ... these are fixed early on in evolution.

The problem is, that we have organism of 'this' general type because the major body plans were 'set' early in history. But this is because of what gould refered to as 'contingency'. There was a wide variety of body types in the cambrian, only a few survived. This means that those other body types are generally lost to the planet, and that the few that are left are the ones that have to fill all other niches. So all animals today have heads with eyes and noses and limbs and the like, because all animals are stemming from the same basic source. When you get to 'behind' that source, to more primitive types, and follow the alternative types up the 'tree' you get types that are entirely different.
So its because of the 'randomness' of whatever was going on in that bygone era that entire bodyplans were completely wiped out, and only a small, essentially random, set survived.

Evolution must proceed till it produces a being capable of turning it off.

? Evolution can be stopped by the destruction of life also. Indeed, even if man could somehow stop his own evolution, evolution would still be going on in all the other populations of living things. This is a rather strange statement.

We then have only variation on the same theme adapting to small changes in the environment or in the animals themselves

This is because of things precisely like what's been discussed. Life expands to fill niches, and populations can change so long as there aren't contstraints on it, phyiscally. So in the beginging, when there were little constraints, there were lots of differnet body plans out there in lots of different animals. Then there was competition and the dangers of existence, this wiped out some groups, and others expanded. Those expanding groups couldn't completely change their entire body plan into something else, because they are 'constrained' to work with the ones they have, not because of some 'neural net' that says 'well you're an animal with segements and a well defined head, you can't become anything else'. And then once we have that, of course the ensuing variation will be variation upon that theme and not be as drastic as it was when there were less contraints.

marg
Occurs I know one is a mammal and the other one a fish.

This is why they have different movements, not because of some 'neural net'.

There are two things operating here, developmental constraints, and environmental constraints. Anything living in the water is constrained by the phsyics of moveing thru water. Hence fish, sharks, whales, even sea going reptiles like icthyosaurs, have the same generalized shape, because to get thru water, you need things like paddles and a streamlined shape etc etc.

The differences are control by their 'developmental' constraints. Fish and sharks, for example, move their whole bodies side to side, because thats a good way to move in water. Icthyosaurs and whales, however, evolved from land dwelling animals, where floping around like a leggless fish doesn't get you anywhere. So in their historical development, their ancestors developed legs, and their body muscularture developed in such a way that the body flexes the spine up and down, to go along with the movemetn of the legs. When land animals return to water, its not a simple thing to get past this; their bodies are thus constrained. So after a long while developing for movement in the water, they get fish like tails and paddles, but they move the tails up and down, because of this ancestral constraint. Its the same reason why they don't re-grow gills, or why they don't lay fish like eggs. And its the same reasons why the paddles of land animals that adapted to the ocean are different that the unorganized spiny rays and fins of fishes. Becuase evoltuion has to work with what its got.