Name: Why Do You Love Your Family?
Uploaded: 2018-09-20T04:03:08.000Z
Duration: 8 min 10 s
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Harrison's favorite hobbies include pooping,
peeing, not sleeping, and costing me a fair

Not exactly the number one qualities you go
looking for in a friend.

Yet, I knew he was the world's most perfect
human the instant I laid eyes on him, I knew

I'd give up everything I have for him, even
my life, without hesitation.

All of that, even though just a few months
ago, we'd never even met.

Staying alive long enough to have healthy
offspring, and getting our traits from one

generation to the next is how we win the big-picture
game of evolution.

Some traits, whether it's being tall, or
having stripes, or six fingers on each hand,

If they increase an organism's chances of
surviving and reproducing, then they'll

This is one of Chuck D's basic principles
in his theory of natural selection.

The measure of how successful a trait is at
making it to the next generation, is called

A trait that's more likely to be passed
on has higher fitness compared to one that's

What we know today, and what Darwin didn't
know back when he was figuring all this out,

is that all these traits from how our bodies
are built to how we think are the product

of thousands of genes, all interacting with
each other and the environment.

Knowing that makes you realize we are survival
machines.

We exist to get our genes into the next generation.

Harrison represents my genes in the next generation.

What did you think, that I just stole someone's
baby?

Now, just for fun, let's say a pack of velociraptors
try to snatch him away.

But I step in and sacrifice my life to save
his!

This self-sacrifice is an extreme example
of altruism, which basically means your pain

Thing is, this kind of risk or ultimate sacrifice–doesn't
immediately make sense when you think of evolution.

If I become velociraptor food, my future chances
of reproducing are now zero.

So why would I give up 100% of my genes, the
ones in my body, to save just half of them,

It might seem like a really bad exchange on
my part, but it actually makes sense.

And some pretty basic math can help explain
why.

Whether an act of altruism is worth it depends
on the relationship between the two parties

The biologist WD Hamilton actually came up
with an equation for this: It factors in the

cost to you, C; the benefit to the other individual,
B; and how closely related the two of you

If the cost to you is less than the benefit
gained by the other individual, multiplied

by that individual's relatedness to you,
then acting altruistically is worth it in

When two individuals aren't related at all,
r will be zero.

Let's say a bus–full of velociraptors–is
careening towards a stranger, completely unrelated

If I push them out of the way and die myself,
I completely lose while the stranger completely

They might print something heroic about me
in the newspaper, but technically this is

not the kind of behavior that evolution rewards.

But if the relatedness is greater than 0,
things work differently.

Let's say the raptor bus is careening towards
my first cousin, and I die saving them.

Because my cousin and I have one-eighth of
our genes in common--our r is 0.125.

If I push my sister out of the way of the
raptor express?

Well, my sister and I have one-half the same
genes, so I only *half* lose.

Understanding this, biologist JBS Haldane
reportedly that he was “prepared to lay

down his life for eight cousins or two brothers.”

But let's say I'm given an even more difficult
choice.

Two busses of velociraptors, one heading towards
my brother and the other my child.

My brother and Harrison both share 50% of
my genes.

Well, I really really hope I never actually
have to make this choice, because I love my

brother too, but I suspect most parents would
save their kid first, and evolution has a

Because Harrison is a tiny baby with his whole
life ahead of him, and my brother and I are

adults, Harrison has the greatest “reproductive
potential” among us.

That's a fancy way of saying that Harrison
is likely to have more children from this

point on than either my brother or I will.

This is where we see the influence of genes
through generations.

Each one of Harrison's future offspring
will share about 25% of my genes.

If he has just two kids, I break even on my
sacrifice.

And if he has more than that, or if any of
his kids have kids of their own, I'd actually

All of these potential grandchildren and great-grandchildren
mean sacrificing myself for my child is a

better decision for the future of my genes
than by letting my child die.

Which I would never let happen, okay buddy?

Now we've been focusing on the most extreme
examples of altruism, giving up your life,

but the fact is altruistic acts are fairly
common among social animals.

Meerkat “guards” keep watch over the colony
and raise an alarm if they spot a predator,

Vampire bats regurgitate blood meals to neighbors
that don't get enough food, and scrub jay