This is simply not the case.
When God asked Cain if he killed his brother Abel, Cain did not say yes.
He said, "I know not: Am I my brother's keeper?" (Genesis 4:9)
Cain lied because he knew that murder was a sin. At this time there are NO Israelites on the earth.
Noah also, knew the commandments of God. As the story is ususally told, Noah filled the Ark with every animal 2 by 2.
"... of every living thing of all flesh, two of every sort shalt thou bring into the ark, to keep them alive with thee; they shall be male and female. Of fowls after their kind, and of cattle after their kind, of every creeping thing of the earth after his kind, two of every sort shall come unto thee, to keep them alive." (Genesis 6:19-20)
The only problem with the above scripture is, that to have understanding on this matter we must continue to read...
3 verses later in chapter 7 we learn more:
"Of every clean beast thou shalt take to thee by sevens, the male and his female: and of beasts that are not clean by two, the male and his female." (Genesis 7:2)
Have you ever heard this part in the song of the story of Noah?
So if it only takes 2 to procreate, the question begs to be asked as to why Noah would bring 7 of every 'Clean Beast' into the Ark?
There are two answers;
1. "And Noah builded an altar unto the LORD; and took of every clean beast, and of every clean fowl, and offered burnt offerings on the altar. And the LORD smelled a sweet savour..." (Genesis 8:18-22)
After the waters of the flood receeded off the earth, Noah being thankful for being spared offered a sacrifice to the Most High God. Noah of course being called a righteous man in chapter 7 verse 1, understood that you can only sacrifice 'Clean' (kosher) animals to the True and Living God. Therefore it was necessary to bring 7 because had he only brought 2 and sacrificed 1 the animal left wouldn't be able to be fruitful and multiply and replensih the earth.
2. "Every moving thing that liveth shall be meat for you; even as the green herb have I given you all things" (Genesis 9:3)
Before the flood of Noah people did not eat meat. It was therefore necessary to bring 7 of every animal that God deemed 'clean' since Noah and his seed would now eat meat.
Some still try and use the last scripture I quoted to say that we can eat ALL meats. Because it says Every moving thing that liveth shall be meat for you, and I given you all things.