🧬 First, a Quick Reminder

In the last lesson, we saw that:

• Genes don’t think, but they give instructions

• Some instructions lead to feelings

• Feelings like fear, love, and anger help us survive

Now let’s look at something even bigger:

How do genes create behavior — without knowing what they’re doing?

What is behavior, first?

🚶 What Is Behavior?

Behavior means what you do.

It includes:

• Walking, talking, sleeping

• Playing, fighting, hugging

• Learning, running, helping

Even blinking or scratching your head is a behavior.

Now — what causes all of this?

Your brain.
And your brain is built by instructions.
Those instructions come from genes.

🧠 Genes Build Your Brain

Your brain is made of billions of cells called neurons.
They connect with each other and send messages.

But how are they built?

Genes tell the brain how to grow, how to wire the neurons, and what to do.

Genes can say things like:

• “Grow this part big”

• “Send these messages faster”

• “Make more cells for movement”

• “React to sounds this way”

So your brain’s shape and reactions — which control your behavior — all start from genes.

😮 But Genes Don’t Think

Let’s be very clear.

Genes do not know what a “hug” or “joke” is.
They don’t have minds.

They just give simple instructions like:

• “Make this protein”

• “Build this brain part this big”

• “Connect these cells”

But when you put millions of instructions together, something amazing happens:

The body starts to act.
And behavior comes out.

That’s why we say:

Genes shape behavior — without planning or knowing what behavior is.

🐶 Animal Behavior: A Good Example

Look at a baby duck.

The moment it hatches, it follows its mother.

Why?

Did anyone teach it?
Did it learn it in school?

No.

Its brain is built in a way that makes it follow the first big thing it sees.

This is called imprinting.

And the reason that behavior happens is because genes built the brain that way.

👶 Human Babies Too!

When a human baby cries, we comfort it.
But why do babies cry in the first place?

No one teaches them.

They do it because:

• It brings help

• It keeps them safe

• It gets attention from adults

This crying behavior is built into the brain — by genes.

Over time, babies that cried were more likely to survive.
So the “crying behavior” gene spread.

😍 Behaviors That Help Genes Spread

Let’s look at some more:

• Smiling makes people like you → Better chance of getting help

• Playing helps you learn → Better chance of surviving

• Staying with family → More safety, more gene-sharing

• Feeling curious → Leads to learning and solving problems

All these behaviors started because they helped bodies survive.
And the genes that caused them were copied more and more.

🧠 Recap

✅ Behavior means what we do: walking, talking, playing
✅ The brain controls behavior
✅ Genes build the brain — so they shape behavior
✅ Genes don’t “know” what they’re doing
✅ But helpful behaviors survive over time