It must have been invented by...

 When and where do you think there were invented?

brain surgery, concrete, eye make-up, water sanitation systems

Read the text and check your predictions

Which information did you find the most surprising? 

How certain is it that the sentences are true? 

Write certainly true (CT), possibly true (PT) or certainly not true (NT). 

1 Egyptians invented make-up.  

2 Both men and women in ancient Egypt wore make-up. 

3. Our ancestors knew about bacteria. 

4. It was a bad idea to perform brain surgery.

5. Roman concrete was good as modern concrete. 

6. Roman concrete was very strong. 

7 The people in the Indus valley were safe from dangerous diseases. 

Find the sentences in the text that told you the answers to Exercise 3. Match the modal structures with their meaning (1-4). Then read the Grammar box to check. 

1 It's very probable or certain that something happened 

2 It's quite possible that something happened. 

3 It's impossible that something happened. 

4 It was wrong to do something. 

GRAMMAR Speculating about the past 

You can talk about possibility and certainty in the X past using the structure: modal verb have X past participle. 

• Use must have if it's very probable or certain that something happened. 

Some of these operations must have been successful. 

• Use may have or might have if it's possible that something happened. 

Egyptians may/might have been the first to use make-up. 

• Use can't/couldn't have if it's impossible that something happened. 

Roman concrete can't have been as strong as modern concrete. 

• Use should/shouldn'"t have to talk about mistakes or express criticism. 

They shouldn't have been doing surgery then.

Practice