Question: What is the first human invention?

"Daddy, what was the first thing invented by humans?"

I can't remember which kid asked this, but I had an old note with this question on it from years ago. 

Answer: Fig-leaf clothes. 

They didn't work well. They didn't cover their shame. Was it due to the cool breeze on those leaves as God walking in the Garden? No, only blood could really cover their shame of sin. So God made them clothes by the first sacrificed animal. The blood covered their sins, and the skin of the animal covered their nakedness.  

But the first inventors specifically mentioned for their inventions were children of Lemech, the 7th from Adam on Cain's side. These would be the evil pillars of society at the time right before the flood. 

Genesis 4:19-24:

And Lemech took two wives: the name of the one was Adah, and the name of the second, Zillah. And Adah bore  

Jabal: he was the father of those who dwell in tents, and [breed] cattle 

And his brother's name was 

Jubal: he was the father of those who handle the harp and pipe. 

And Zillah, she also bore 

Tubal-Cain, the forger of every kind of tool of brass and iron. 

And the sister of Tubal-Cain was Naamah. 

And Lemech said to his wives: 

Adah and Zillah,
     hear my voice, 
Ye wives of Lemech,
     listen to my speech.
For I have slain a man for my wound,
     and a youth for my bruise.
If Cain shall be avenged seven-fold;
     Lemech seventy and seven fold.