If Genesis says all plants and all animals are put on earth to be eaten by man how come we have man made dietary laws?
Thank you very much for your interesting questions. First of all, we must realize that the Kosher dietary laws that we have today are not “man made”, they were given to the Jewish nation by G-d at Sinai. They are clearly spelled out in Leviticus Chapter 11, and in Deuteronomy Chapter 14.
Secondly, I assume that the verses in Genesis that you refer to are in 1:29-30. A careful reading will show (at least in the Hebrew original) that although man is to have dominion over animals and plants, only plants should be eaten by man. In other words, man was originally to have been a vegetarian! Only after the Great Flood does G-d tell Noah (Genesis 9:3) that man is now permitted to eat the flesh of animals, and the only restriction being not to eat limbs and flesh removed from animals while they are alive, which is applicable to all humanity even today. (In case this sounds strange to you, please note that in the October 1998 National Geographic there is an article about the state of Nebraska, and mentions that one of the delicacies of the livestock raising farmers there are “prairie oysters”, the fried testicles of the recently castrated calves. These are “non-Kosher” even for a non-Jew.)
However, the Kosher dietary laws as known today are only applicable to the Jewish nation from the time of the giving of the Torah at Sinai. Although our Rabbis teach us that our forefathers did keep the dietary laws even prior to Sinai, it was not obligatory upon them as a binding law to do so. There are other examples of laws that only came into effect from the time of our formation as a nation at Sinai. One example would be that although today we are not permitted to marry two sisters, our Forefather Jacob actually did marry two sisters! As a matter of fact, it can be argued that if Cain and Abel had not married their sisters, we would not be here today! Therefore, even though permission was grated to humanity in the times of Noah to eat all animals, which is applicable to non-Jews even today, additional restrictions were placed on the Jewish nation at the time that the Torah was given to them at Sinai.