Myths and misconceptions about evolution. Let's talk about evolution. You've probably heard that some people consider
it controversial, even though most scientists don't. But even if you aren't one of those people and you think you have a pretty
good understanding of evolution, chances are you still believe
some things about it that aren't entirely right, things like, "Evolution is organisms
adapting to their environment." This was an earlier, now discredited, theory of evolution. Almost 60 years before Darwin
published his book, Jean-Baptiste Lamarck proposed that creatures evolve by developing certain traits over their lifetimes and then passing those
on to their offspring. For example, he thought that because giraffes spent their lives stretching to reach leaves
on higher branches, their children would be
born with longer necks. But we know now that's not
how genetic inheritance works. In fact, individual organisms
don't evolve at all. Instead, random genetic mutations cause some giraffes to be
born with longer necks, and that gives them
a better chance to survive than the ones who weren't so lucky, which brings us to "survival of the fittest". This makes it sound
like evolution always favors the biggest, strongest, or fastest creatures, which is not really the case. For one thing, evolutionary
fitness is just a matter of how well-suited
they are to their current environment. If all the tall trees suddenly died out and only short grass was left, all those long-necked giraffes would be at a disadvantage. Secondly, survival is not
how evolution occurs, reproduction is. And the world if full of creatures like the male anglerfish, which is so small and ill-suited
for survival at birth that it has to quickly find
a mate before it dies. But at least we can say that if an organism dies
without reproducing, it's evolutionarily useless, right? Wrong! Remember, natural selection happens not at the organism level, but at the genetic level, and the same gene
that exists in one organism will also exist in its relatives. So, a gene that makes an animal
altruistically sacrifice itself to help the survival
and future reproduction of its siblings or cousins, can become more widespread than one that is solely concerned
with self-preservation. Anything that lets more copies of the gene pass on to the next generation will serve its purpose, except evolutionary purpose. One of the most difficult things
to keep in mind about evolution is that when we say things like, "Genes want to make more
copies of themselves," or even, "natural selection," we're actually using metaphors. A gene doesn't want anything, and there's no outside mechanism that selects which genes
are best to preserve. All that happens is that random
genetic mutations cause the organisms carrying them to behave or develop in different ways. Some of those ways result in more copies of the mutated gene being passed on, and so forth. Nor is there any predetermined plan progressing towards an ideal form. It's not ideal for the human
eye to have a blind spot where the optic nerve exits the retina, but that's how it developed, starting from a simple photoreceptor cell. In retrospect, it would have been much more advantageous for humans to crave nutrients and vitamins rather than just calories. But over the millenia, during which our ancestors evolved, calories were scarce, and there was nothing to anticipate that this would later change so quickly. So, evolution proceeds blindly, step by step by step, creating all of the diversity
we see in the natural world.
