DNA is made of a long chain of nucleotides. There's, in essence, 4 different nucleotides.
3 nucleotides in a row code for 1 amino acid. Then long chains of amino acids bunch and
fold and form a proteins. Proteins basically do or control all the things
in the cell. From being enzymes, to constructing cell membranes, to.....
all the other stuff.
The DNA sequence can change by bits moving around, mistakes in the way it's copied, environmental
damage... and whatnot, that leads to different amino acids being coded for and different
proteins being made. And DNA is can be shuffled around, and mixed
and matched from things like sexual reproduction. These are some of the ways our blueprints
can change, this is sorta HOW things evolve. To better understand WHY things evolve, let's
first look at why things don't evolve. If something dies before it reproduces...
then it's not evolving. If that DNA doesn't get copied into a new organism.
When we're looking at evolution, we're basically looking at the changes in the blueprints along
lines of reproduction. So if an organism leaves behind no offspring, those blueprints aren't evolving.
Keep in mind, it's not the DNA itself changing.
It's just the information: the order of nucleotides, that's being copied and changed. New DNA is
assembled with each new cell, and the old DNA eventually falls apart.
The thing that passes from one individual to the next, is the information, the order
of the nucleotides. Overtime, the incidental and random changes in the sequence, and whatever
works long to reproduce again, results in all the different genomes and organisms we see.
Evolution doesn't AIM, for any organism or trait.
All the organisms that we see today are just the ones that came from a unbroken line of .....
organisms that reproduced before dying. With all those inherited
changes in their blueprints. So... no organism that is around today is
any more or less "evolved" than any other that is around today. They've all reproduced
down a line from the beginning of life to the present. And they're all equally successful.
So to pass on their blueprints. Creatures need to get nutrients and grow, find a mate,
if your sexual, and not die long enough reproduce. Since it's your genes that influence these
things, genes will have a better chance of getting passed on if they code for traits
that help survival and reproduction. Like genes for beaks that get at more food, genes
for camouflage that make them hide from predators, or genes for something that makes sounds to
attract mates. If a gene codes for a trait that doesn't help
reproduction, then it'll have a decreased chance of being passed on.
Like, let's say a bird had some genes that led to some cool horns.
Maybe they look impressive, but the extra weight prevents it from flying.
And all the energy it spent trying to make those horns, could have gone to something
more useful. So it can't get food as easily and it's dies
a lot from getting eaten by bears and other ground predators. Which decreases their chances
of reproducing. If there were a number of birds in a population
just for whatever reason, they wouldn't survive as long or reproduce as much as those without
these gene. Over time you'll stop seeing this particular gene for horns because those with
it, have an increased chance of dying before reproducing.
This is the basis for WHY things evolve. If a gene codes for something that helps survival
or reproduction, then it'll reproduce more. It helps not to think about the individual
as the thing that's being replicated. But the genes.
It's counter intuitive to do, because Gene's mostly don't reproduce on their own... mostly....
and their reproduction requires the actions of that entire vessel. So genes mostly code
for traits that help their vessel. But only insofar that it helps themselves reproduce.
Remember, the vessel dies, the old DNA falls apart. It's the code that goes from one generation
to the next. That's the thing being reproduced. The information stored as DNA, is the thing
that has to benefit from the protein. In terms of evolution, the individual doesn't matter
as much. Let's look at an example.
Let's presume there's some sort of...set of genes that code for something that makes an
organism care for its offspring. Like gene's for paternal love or something. These genes
actually hurt the individual, the parent's chance of survival and future reproduction.
They're spending time and energy caring for young when it could and just make more and
leave behind more copies. Since this gene hurts the individual, how could it survive
and be passed on? Why doesn't this gene go away the same way genes for sick ass horns on a bird would.
Why doesn't every animal abandon its young the way a lot of fish do?
It's because the offspring also has this child caring gene. This gene leads to a trait that
increases the reproduction of a copy of itself, in the child. So even though this gene hurts
the individual that it's in and ultimately itself, it still increases the survival of
futures copies of that gene. Which keeps it in circulation.
If we're looking at it from the perspective of the gene, then everything outside of the
gene, even other genes of the same organism, is just the environment to it.
Like, those same genes for horns that didn't work with the genes of the bird, in a different
environment with different genes, may be beneficial for reproduction.
The gene can code for any protein, that's what genes do. That protein is that genes
effect on the world outside itself. It can do anything that a chain of amino acids can
do. But if that protein does anything but support that gene's reproduction in some way.
Meaning it's not helping this happen, or helping this happen in the child like we saw, then...
while that's all fine and good. There's not really a strong reason to continue to see
that gene after that individual. Each individual is a hodge podge of a whole
bunch of different genes coding for a whole bunch of different proteins.
And with sexual reproduction, genes are shuffled around with each new individual. What this
means is that over long periods of time, genes kinda sorta act on their own.
Let's say there's one gene that codes for a trait that helps reproduction and another
gene that hurts reproduction... and let's say that that makes sense. Sure the red gene
will hurt the blue gene sometimes when they're together. But in other instances... for example,
in instances when they are not together, this individual will out compete this one, meaning
it will make more or better children. Some of them will die, as happens, they'll get
eaten or they'll fall into a snake pit. But since there's more of these guys and they're
theoretically better at surviving. This blue gene will have a better chance of remaining
than this red gene, even though they're together sometimes.
What is being implicated, by saying everything outside the gene is the environment to it,
is that the gene won't code for something that help something else. Genes code to help
the vessel they're in and have evolved to work well with the other genes in that organism
... but only because it helps itself. If a gene helps something else, at its own expense,
then each generation this gene will have a decreased chance of being passed.
Anyways, to summarize. Genes are shuffled around with each new organism, so when you
wanna look at what's being passed down and evolving you gotta look at the individual
genes. The more a gene helps reproduction, the more it'll reproduce and the more you
see it. The less a gene helps the less you see it. Such that, in the end, or I guess
in the present, the genes that remain, tend to be ones that code for traits that are relatively
self serving for reproduction.
Evolutionary theory people often talk about things only in terms of reproduction. Like: "camouflage is good because it helps reproduction".
I think because reproduction is the more important thing. It's sort of a short hand for saying:
"Camouflage helps survival so that the organism can go off and reproduce more." But can there be
a creature that lives forever and maybe only reproduces....
... more adaptive behaviours based on it all. Things without brains tend to have less
involved behaviours. Things along the lines of: "if notice certain chemical, then follow
certain chemical". So instead of it being a matter of: things that followed that chemical
left behind more copies than things that did not follow that chemical. Things with brains
can learn in one lifetime which chemicals to eat and with to leave alone. Some behaviours
are inherited before birth....