God informs Noah and his sons of several things about the new, postflood world here.
First, the animals had instinctively come to Noah - we have
already explored whether there were zoos or whether a single continent
like what scientists call Pangea could have let them come without any
issues with oceans. Now, things were different.
Whether mankind ate animals or was vegetarian before is
uncertain, but many nowadays think only here did people start to eat
meat. It is, however, also possible that the next few verses indicate
that people ate it and God's warning was about a sin which had occurred
before.
Either way, the animals lost their familiarity with
mankind. Animals almost certainly had killed people before, since they
had begun early to hunt other animals for food. Bit, their appetites for
any meat had been suppressed by God.
This has modern equivalents, in fact. Zoos in World War 2
in Britain couldn't get meat to feed the large lions and other animals,
so the lions and other beasts which normally ate meat kept full eating
grass and other plants.
