WEBVTT

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Myths and misconceptions about evolution.

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Let's talk about evolution.

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You've probably heard

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that some people consider
it controversial,

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even though most scientists don't.

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But even if you aren't one of those people

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and you think you have a pretty
good understanding of evolution,

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chances are you still believe
some things about it

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that aren't entirely right,

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things like,

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"Evolution is organisms
adapting to their environment."

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This was an earlier,

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now discredited,

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theory of evolution.

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Almost 60 years before Darwin
published his book,

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Jean-Baptiste Lamarck proposed

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that creatures evolve by developing

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certain traits over their lifetimes

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and then passing those
on to their offspring.

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For example, he thought

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that because giraffes spent their lives

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stretching to reach leaves
on higher branches,

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their children would be
born with longer necks.

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But we know now that's not
how genetic inheritance works.

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In fact, individual organisms
don't evolve at all.

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Instead, random genetic mutations cause

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some giraffes to be
born with longer necks,

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and that gives them
a better chance to survive

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than the ones who weren't so lucky,

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which brings us to

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"survival of the fittest".

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This makes it sound
like evolution always favors

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the biggest,

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strongest,

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or fastest creatures,

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which is not really the case.

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For one thing, evolutionary
fitness is just a matter

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of how well-suited
they are to their current environment.

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If all the tall trees suddenly died out

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and only short grass was left,

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all those long-necked giraffes

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would be at a disadvantage.

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Secondly, survival is not
how evolution occurs,

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reproduction is.

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And the world if full of creatures

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like the male anglerfish,

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which is so small and ill-suited
for survival at birth

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that it has to quickly find
a mate before it dies.

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But at least we can say

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that if an organism dies
without reproducing,

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it's evolutionarily useless, right?

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Wrong!

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Remember, natural selection happens

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not at the organism level,

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but at the genetic level,

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and the same gene
that exists in one organism

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will also exist in its relatives.

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So, a gene that makes an animal
altruistically sacrifice itself

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to help the survival
and future reproduction

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of its siblings or cousins,

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can become more widespread

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than one that is solely concerned
with self-preservation.

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Anything that lets more copies of the gene

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pass on to the next generation

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will serve its purpose,

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except

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evolutionary purpose.

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One of the most difficult things
to keep in mind about evolution

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is that when we say things like,

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"Genes want to make more
copies of themselves,"

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or even,

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"natural selection,"

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we're actually using metaphors.

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A gene doesn't want anything,

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and there's no outside mechanism

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that selects which genes
are best to preserve.

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All that happens is that random
genetic mutations

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cause the organisms carrying them

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to behave or develop in different ways.

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Some of those ways result in more copies

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of the mutated gene being passed on,

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and so forth.

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Nor is there any predetermined plan

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progressing towards an ideal form.

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It's not ideal for the human
eye to have a blind spot

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where the optic nerve exits the retina,

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but that's how it developed,

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starting from a simple photoreceptor cell.

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In retrospect, it would have been

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much more advantageous for humans to crave

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nutrients and vitamins

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rather than just calories.

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But over the millenia,

NOTE Paragraph

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during which our ancestors evolved,

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calories were scarce,

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and there was nothing to anticipate

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that this would later change so quickly.

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So, evolution proceeds blindly,

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step

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by step

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by step,

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creating all of the diversity
we see in the natural world.