Although a bit off topic I will add to my above comments the following ideas.
The body can change somewhat due to changes in the gene pattern. The other poster suggested this is caused by "random addition or deleted" gene mutations. Random meaning what? That is anyone's guess. Now the term "random" might work for an overall blanket perception. But when you get down to each single alteration in a gene we could likewise a particular cause for that change. Even if accidental it is still a particular cause for the effect taking place.
Example: if fish is brain food then eating fish might improve one's ability to think, but do genes effect the brain or the other way around? Or both ways.
Are people in Japan who eat a lot of fish smarter then cowboys who eat a lot of hambugers? Hmm?
But that is not my point anyway.
My question is "what causes those seemingly ramdom changes in our genes or DNA"? Or do those changes occur for no particular reason at all?
A Rattlesnake evolved the use of posion fangs where as other snakes living in the same enironmental locations did not. Hmm? Why some and not all?
Were those differences created by gene pool mutations or not? Do we wish to believe in limited evolution or do we wish to go "all the way" by thinking that each kind of snake evolved and alternated from one common ancestor?
That the tiny domestic kitty and the lion both had common roots, all somehow united as a "family" with their own original "Eve cat" way back then?
Now you can have tiny cats and big cats living in the same environments for thousands of years and so adaptation to the environment would leave open some room for doubt.
However the word "random" as a cuase tells us nothing, it is nearly useless.
And so I came up with another idea that I cannot prove. Here it is.
Some evolutionary changes are caused by a natual factor called "yearning".
Yearning is like wishing upon a star but does not demand thinking. Without even knowing that they are doing it creatures can yearn for this or that so that can have some advantage, security, or ability. Need generates that yearning. Once an eel was in rough waters and yearned for some help and at that moment the principle of electrical currents was unused, so the eel was able to adopt that principle and it became an electric eel. Somehow the yearning could manifest a principle such as electricity in the animals body.
For such events to happen the world (nature) had to have "fomulative stages" like those of young children. As nature became mature those drastic changes slowed down because it was no longer in that formuative stage of evolution.
If the yearning did not effect such internal manifestations (alterations) then the "crying out for help" was answered by a larger memory bank in nature, as discribed by Peter Russell. (book - the Global Brain). I will not suggest "God" becuase this is not a religious debate forum. Although we do have evidence of praying humans that evolved higher then the Chimps and so forth, they also ate more fish - like smart Dolphins do.
However most everything eats fish and not everything is as smart as I is.
But in fact people did and do yearn to know everything, and that yearning which started back just before recorded history has spearheaded us on towards our present day intelligent status. I guess those chimps just yearned to monkey around.
Now back to the background data for this concept. The DNA strand is like an informational collective antenna and it can recieve and download info from out of the blue - from that memory bank surrounding the planet. Morphic Field? That DNA stand is like a tree of knowledge that programs the rest of the body in co-operation with the brain. And becomes a generational communicator of knowledge due to reproduction. That is - knowledge in use - not book knowledge.
The yearning ties in with that informational highway called our DNA - data base.
If a monkey in Africa learns a new way to crack open shells then in the next generation the monkeys in South America will "know the same trick". That is because the DNA antenna of the South American monkey can pick up that info from that global memory bank.
Yearning works like a gravity force that pulls data from out of that cosmic like memory bank, so that it can be used or manifested into being by the creature yearning for some sort of help.
Articles and Papers - Scientific Papers - Morphic Resonance - Morphic Fields The Global Brain